Article

THE FINE STRUCTURE OF GREEN BACTERIA

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

The fine structure of several strains of green bacteria belonging to the genus Chlorobium has been studied in thin sections with the electron microscope. In addition to having general cytological features typical of Gram-negative bacteria, the cells of these organisms always contain membranous mesosomal elements, connected with the cytoplasmic membrane, and an elaborate system of isolated cortical vesicles, some 300 to 400 A wide and 1000 to 1500 A long. The latter structures, chlorobium vesicles, have been isolated in a partly purified state by differential centrifugation of cell-free extracts. They are associated with a centrifugal fraction that has a very high specific chlorophyll content. In all probability, therefore, the chlorobium vesicles are the site of the photosynthetic apparatus of green bacteria.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... Chlorosomes were discovered in 1964 and described as oblong bodies attached to the inner side of the cytoplasmic membrane in thin sections of cells from Chlorobi species (Fig. 1) (Cohen-Bazire et al., 1964). Subsequently, chlorosomes were found in three bacterial phyla: most of the known species of Chlorobi (all known members of the family Chlorobiaceae, green sulfur bacteria), certain Chloroflexi species (the majority of the known members of the class Chloroflexi and "Candidatus Chlorothrix halophila" (Klappenbach and Pierson, 2004), filamentous anoxygenic phototrophs, formerly known as green non-sulfur bacteria), and one bacterium belonging to Acidobacteria . ...
... (Imhoff and Thiel, 2010), showing chlorosomes (white bodies labeled as 'cv', chlorobium vesicles; one of the chlorosomes is highlighted by the red rectangle) attached to the cytoplasmic membrane. The figure is from the original paper in which chlorosomes were first described (Cohen-Bazire et al., 1964, reproduced with permission from Rockefeller University Press). (b) Schematic diagram of the shape and interior of a typical chlorosome. ...
Chapter
Full-text available
Chlorosomes are light-harvesting complexes found in photosynthetic bacteria belonging to three diverse phyla: Chlorobi, Chloroflexi and Acidobacteria. They are composed of bacteriochlorophylls with minor contributions from proteins, lipids, carotenoids and quinones. Proteins are confined to the surface of the chlorosome while most bacteriochlorophyll molecules are found within the interior where they assemble into aggregates. These aggregates consist of lamellar structures, in which bacteriochlorophylls form curved layers while hydrophobic esterifying alcohols of bacteriochlorophylls from adjacent layers interdigitate and hold the system together. Such an arrangement supports strong excitonic coupling between the pigments within a layer and enables efficient excitation energy transfer. This chapter surveys general features of the chlorosome, including structure, energy transfer, photoprotective mechanisms and assembly.
... She also worked on the structure and composition of phycobilisomes in cyanobacteria, and on chromatic adaptation (Glazer and Cohen-Bazire 1971;Bryant and Cohen-Bazire 1981). Cohen-Bazire became an expert electron microscopist and her micrographs helped lead to our current understanding of the membrane architecture of thylakoids in cyanobacteria, 'chromatophores' (intracytoplasmic membranes) in purple phototrophic bacteria and chlorosomes in green phototrophic bacteria (Cohen-Bazire and Kunisawa 1960;Cohen-Bazire et al. 1964;Guglielmi and Cohen-Bazire 1984). ...
Chapter
Full-text available
This paper introduces the third and final part of the ‘millennium celebrations of historical highlights of photosynthesis research.’ Part 1 (308 pages) was published in October 2002 as Vol. 73 of the journal Photosynthesis Research, and Part 2 (458 pages) was published in July 2003 as Vol. 76. Here, we recognize particularly the work of three major contributors to our understanding of photosynthesis: Roger Stanier (1916–1982); Germaine Cohen-Bazire (Stanier) (1920–2001); and William Arnold (1904–2001). We also introduce the historical papers contained in this volume; consider the legacy of Alfred Nobel (1833–1896); and identify Nobel prizes of special relevance to understanding the capture, conversion, and storage of light energy in both anoxygenic and oxygenic photosynthesis.
Article
— Chlorosomes isolated from two types of green sulfur bacteria, Chlorobium tepidum which contains bacteriochlorophyll c (BChl c) and the BChl e-containing Chlorobium phaeobacteroides, were subjected to alkaline treatment (pH 12.7 at 40°C for 20 min). This caused selective degradation of BChl a, whereas BChl c or e were not affected. Chlorobiumquinone in the Chlorosomes was partially degraded by the alkaline treatment but menaquinone was unchanged. Fluorescence decay kinetics showed that alkaline treatment disrupted energy transfer from BChl c or e to BChl a under reducing conditions. However, this did not give rise to any substantial increase in the excited state lifetime of BChl e in C. phaeobacteroides Chlorosomes, while for C. tepidum a decrease in the BChl c lifetime was found. The steady-state fluorescence of chlorosomes is highly dependent on the redox potential such that emission is quenched in oxidizing environments. Alkaline treatment diminished this quenching effect and caused a doubling in the BChl c or e emission intensity under aerobic conditions. Single-photon timing experiments confirmed that alkaline treatment inhibits the energy trapping process operative under aerobic conditions. These effects of alkaline treatment on the fluorescence intensity and decay kinetics are likely to be related to the depletion in BChl a or in Chlorobiumquinone or a combination of these.
Article
Reveals crucial influence (epicellular biomineralization) of small (<1 μm) coccoid cyanobacteria in the calcification process in Green Lake. Microscopic examination shows that the bioherms are actually modern thrombolitic. Groundwater enters Green Lake along the Syracuse Formation-Vernon Shale contact (~10 m depth) and the contact between the green and red shale facies of the Vernon Shale (~18 m depth). Electron microscopy of the bacteria from the oxic-anoxic interface reveals two predominant species of anoxygenic phototrophic sulfur bacteria and a facultative anoxygenic filamentous cyanobacterium. -from Authors
Article
Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria.
Article
Developmental biology and cell differentiation of photosynthetic prokaryotes are less noticed fields than the showpieces of eukaryotes, e.g. Drosophila melanogaster. The large metabolic versatility of the facultative purple bacteria and their great capability to adapt to different ecological conditions, however, aroused the inquisitiveness to investigate the process of cell differentiation and to use these bacteria as model system to study structure, function and biosynthesis of the photosynthetic apparatus. The great progress in research in this field paved the way to study principal mechanisms of cellular organization and differentiation in these bacteria. In this article, the history of the research on membrane structure and development of anoxygenic photosynthetic prokaryotes during the last 45 years is described. A personal account of how I entered the field through research on the phototaxis of cyanobacteria is given. Intracytoplasmic membranes (ICM) were detected by electron microscopy in cyanobacteria and in purple non-sulfur bacteria. The formation of ICM by invagination of the cytoplasmic membrane in purple bacteria was observed for the first time. Investigations on the effect of changes in oxygen tension and light intensity on the formation of pigments and intracytoplasmic membranes followed. The isolation, purification, and analysis of light-harvesting complexes and of pigment-binding proteins was the next step of our research. Lipopolysaccharides and peptidoglycans were detected and analyzed in the outer membrane of photosynthetic bacteria. Functional membrane differentiation includes variations in the rates of photophosphorylation and electron transport. Molecular genetic approaches have initiated the investigation of transcriptional regulation and the analysis of correlation between pigment and protein synthesis. Molecular analysis of assembly of light-harvesting complexes and membrane differentiation are the present aspects of our research. Cell differentiation has been considered under evolutionary view.
Article
Whole cells and isolated chlorosomes (antenna complex) of the green photosynthetic bacterium Chloroflexus aurantiacus have been studied by absorption spectroscopy (77 K and room temperature), fluorescence spectroscopy, circular dichroism, linear dichroism and electron spin resonance spectroscopy. The chlorosome absorption spectrum has maxima at 450 (contributed by carotenoids and bacteriochlorophyll (BChl) a Soret), 742 (BChl c) and 792 nm (BChl a) with intensity ratios of 20:25. The fluorescence emission spectrum has peaks at 748 and 802 nm when excitation is into either the 742 or 450 nm absorption bands, respectively. Whole cells have fluorescence peaks identical to those in chlorosomes with the addition of a major peak observed at 867 nm. The CD spectrum of isolated chlorosomes has an asymmetric-derivative-shaped CD centered at 739 nm suggestive of exciton interaction at least on the level of dimers. Linear dichroism of oriented chlorosomes shows preferential absorption at 742 nm of light polarized parallel to the long axis of the chlorosome. This implies that the transition dipoles are also oriented more or less parallel to the long axis of the chlorosome. Treatment with ferricyanide results in the appearance of a 2.3 G wide ESR spectrum at g 2.002. Whole cells grown under different light conditions exhibit different fluorescence behavior when absorption is normalized at 742 nm. Cells grown under low light conditions have higher fluorescence intensity at 748 nm and lower intensity at 802 nm than cells grown under high light conditions. These results indicate that the BChl c in chlorosomes is highly organized, and transfers energy from BChl c (742 nm) to a connector of baseplate BChl B792 (BChl a) presumably located in the chlorosome baseplate adjacent to the cytoplasmic membrane.
Article
Efforts for building hybrid solar cells which have an antenna system similar to the chlorosomes of green photosynthetic bacteria are reviewed and discussed in the context of the current state-of-the-art.
Article
Chlorosomes, the major antenna complexes in green sulphur bacteria, filamentous anoxygenic phototrophs, and phototrophic acidobacteria, are attached to the cytoplasmic side of the inner cell membrane and contain thousands of bacteriochlorophyll (BChl) molecules that harvest light and channel the energy to membrane-bound reaction centres. Chlorosomes from phototrophs representing three different phyla, Chloroflexus (Cfx.) aurantiacus, Chlorobaculum (Cba.) tepidum and the newly discovered "Candidatus (Ca.) Chloracidobacterium (Cab.) thermophilum" were analysed using PeakForce Tapping atomic force microscopy (PFT-AFM). Gentle PFT-AFM imaging in buffered solutions that maintained the chlorosomes in a near-native state revealed ellipsoids of variable size, with surface bumps and undulations that differ between individual chlorosomes. Cba. tepidum chlorosomes were the largest (133×57×36 nm; 141,000 nm(3) volume), compared with chlorosomes from Cfx. aurantiacus (120×44×30 nm; 84,000 nm(3)) and "Ca. Cab. thermophilum" (99×40×31 nm; 65,000 nm(3)). Reflecting the contributions of thousands of pigment-pigment stacking interactions to the stability of these supramolecular assemblies, analysis by nanomechanical mapping shows that chlorosomes are highly stable and that their integrity is disrupted only by very strong forces of 1000-2000 pN. AFM topographs of "Ca. Cab. thermophilum" chlorosomes that had retained their attachment to the cytoplasmic membrane showed that this membrane dynamically changes shape and is composed of protrusions of up to 30 nm wide and 6 nm above the mica support, possibly representing different protein domains. Spectral imaging revealed significant heterogeneity in the fluorescence emission of individual chlorosomes, likely reflecting the variations in BChl c homolog composition and internal arrangements of the stacked BChls within each chlorosome.
Article
Description of intra-chlorosome and from chlorosome to baseplate excitation energy transfer in green sulfur bacteria and in filamentous anoxygenic phototrophs is presented. Various shapes and sizes, single and multi-walled tubes, cylindrical spirals and lamellae of the antenna elements mimicking pigment organization in chlorosomes were generated by using molecular mechanics calculations, and the absorption, LD, and CD spectra of these were predicted by using exciton theory. Calculated absorption and LD spectra were similar for all modeled antenna structures, on the contrary CD spectra turned out to be sensitive to the size and pigment orientations in the antenna. It was observed that bringing two tubular antennae at close enough interaction distance exciton density of the lowest energy state became localized on pigments facing each other in the antenna dimer. Calculations predicted for stacked tubular antenna elements extremely fast, faster than 500 fs, intra-chlorosome energy transfer towards the baseplates in the direction perpendicular to the chlorosome long axis. Down hill excitation energy transfer according our model is driven by interactions of the antennae with their immediate surroundings. Energy transfer from the chlorosome to the baseplate, consisting of 2D lattices of monomeric and dimeric bacteriochlorophyll a molecules, was predicted to occur in 5 to 15 ps, in agreement with experimental findings. Advancement of excitation through a double - tube antenna stack, a model for antenna element organization in chlorosomes of green sulfur bacteria, to a monomeric baseplate was visualized in space and in time.
Article
Chlorosomes of the thermophilic green sulfur bacteriumChlorobium tepidum have been isolated and their polypeptides analyzed by polyacrylamide gel electrophoresis and amino acid sequencing. These chlorosomes were shown to contain nine different polypeptides ranging in mass from approximately 6 to 27 kDa. ThecsmA gene, encoding a highly abundant chlorosome protein with a mass of 6.2 kDa, were cloned and sequenced from bothChlorobium vibrioforme strain 8327D andChlorobium tepidum. The gene from both species predicts identical proteins of 79 amino acid residues, and a comparison of the deduced sequence with that determined for the protein indicates that 20 amino acid residues are post-translationally removed from the carboxyl-terminus of the CsmA precursor. Transcript analyses showed that inChlorobium tepidum thecsmA gene is encoded on two transcripts of approximately 350 and 940 nucleotides; the smaller transcript probably results from processing of the larger RNA molecule. Transcription of the longer mRNA initiates 68 basepairs upstream from the start codon of a second open reading frame that is located 154 nucleotides 5′ tocsmA and that predicts a protein of 139 amino acid residues. The amino-terminal sequence determined for a 14.5 kDa polypeptide in the chlorosomes ofChlorobium tepidum matched the sequence deduced from this open reading frame except for the absence of the initiator methionine residue; accordingly, this gene has been namedcsmC. A comparison of the genomic organization of thecsmA loci inChlorobium vibrioforme, Chlorobium tepidum, andChloroflexus aurantiacus were found to be surprisingly similar.
Article
Highly purified fractions of chlorosomes and cytoplasmic membranes were isolated from Chloroflexus aurantiacus Ok-70-fl and Chlorobium limicola 6230. These fractions were comparatively analyzed for their pigmentation, phospholipid, glycolipid, and cytochrome c content as well as for their specific activities of succinate dehydrogenase and NADH-oxidase. The data showed that there are some differences in pigmentation and phospholipid content between the isolated fractions of Chloroflexus and Chlorobium. Chlorosomes of Chloroflexus contained a specific BChl a-complex with a characteristic absorption maximum at about 790 nm. This BChl a-complex could not be detected in spectra of chlorosomes from Chlorobium. The near infrared region of the spectra of the isolated cytoplasmic membranes of both organisms revealed considerable differences: The BChl a-complexes of Chloroflexus membranes exhibited peaks at 806 and 868 nm whereas the membranes of Chlorobium had a single BChl a-peak at 710 nm. In contrast to the findings with Chlorobium the chlorosomes of Chloroflexus contained at least twice as much phospholipids as did the cytoplasmic membranes. In Chlorobium the phospholipid content of cytoplasmic membranes is three times that of their chlorosomes. The distribution of all other components (carotenoid composition, enzyme activities, cytochrome c content, and glycolipids) was about the same in both strains. From the data it was concluded that differences in the organization of the photosynthetic apparatus are mainly based on differences of the organization of the photosynthetic units in the cytoplasmic membrane and probably the kind of linkage of the light harvesting system in the chlorosomes with the reaction center in the cytoplasmic membranes.
Article
Chlorosomes are efficient light-harvesting antennas containing up to hundreds of thousands of bacteriochlorophyll molecules. With massively parallel computer hardware, we use a non-perturbative stochastic Schrödinger equation, while including an atomistically-derived spectral density, to study excitonic energy transfer in a realistically sized model. We find that fast short-range delocalization leads to robust long-range transfer due to the antennae's concentric-roll structure. Additionally, we discover anomalous behavior arising from different initial conditions, and outline general considerations for simulating excitonic systems on the nanometer to micrometer scale.
Article
Chlorosomes from Chlorobium tepidum have been treated with alcohol-saturated buffers, followed by dilution to the buffers with half the saturated concentrations. Morphologic changes during this process have been statistically investigated by dynamic light scattering technique combined with electron microscopy to obtain the complete information on shape, size and distribution, while spectral properties have been studied by absorption, CD and magnetic circular dichroism. Three alcohols (1-hexanol, 1-butanol and phenol) have been found to produce nearly reversible conversion of absorption spectra despite the more than 15-times difference in the alcohol concentration. It is shown that the degree of saturation, not the alcohol concentration, is the key factor for the complete conversion of bacteriochlorophyll c in chlorosomes from the aggregated state to the monomeric form. We have observed substantial changes in the shape, size and distribution at each step of the treatment with 1-hexanol, indicating that the whole process is morphologically irreversible. Comparison of the morphologic changes with the corresponding spectroscopic behaviour suggests that the relative overall size rather than the shape and distribution may be a more important factor affecting the spectral properties.
Article
Full-text available
Chlorosomes are the distinguishing light-harvesting antenna complexes that are found in green photosynthetic bacteria. They contain bacteriochlorophyll (BChl) c, d, e in natural organisms, and recently through mutation, BChl f, as their principal light-harvesting pigments. In chlorosomes, these pigments self-assemble into large supramolecular structures that are enclosed inside a lipid monolayer to form an ellipsoid. The pigment assembly is dictated mostly by pigment-pigment interactions as opposed to protein-pigment interactions. On the bottom face of the chlorosome, the CsmA protein aggregates into a paracrystalline baseplate with BChl a, and serves as the interface to the next energy acceptor in the system. The exceptional light-harvesting ability at very low light conditions of chlorosomes has made them an attractive subject of study for both basic and applied science. This review, incorporating recent advancements, considers several important aspects of chlorosomes: pigment biosynthesis, organization of pigments and proteins, spectroscopic properties, and applications to bio-hybrid and bio-inspired devices.
Article
Scanning Electron Microscopy (SEM) is used to image geomicrobiological samples, typically containing interfaces between ?hard and soft materials? such as minerals and cells, which represent challenges for artifact-free preparation for high-resolution imaging. We used cell-mineral aggregates produced during microbial Fe(II) oxidation and Fe(III) reduction to evaluate different sample preparation and imaging techniques. Both rapid freezing and standard critical point drying (CPD) preserve structures of geomicrobiological samples, at least the ones obtained for Fe(II)-oxidizing and Fe(III)-reducing bacteria, without artifacts. We recommend a SEM sample preparation scheme for geomicrobiological specimens and discuss critical parameters like fixation, dehydration, coating, and acceleration voltages.
Article
The optical properties of the supramolecular aggregates formed by semisynthetic 31-methoxy zinc chlorins were studied theoretically using an exciton theory description. The exciton coupling between the chromophores was calculated using a transition density formalism, making it possible to distinguish stereochemical differences that arise from the facial orientations of the chiral zinc chlorin molecules in the aggregate. It is shown that the precise stereochemical orientation of the molecules inside the stack strongly influences the observed optical properties. These calculations point to a structure with alternating twist angles along the stack, suggesting a different orientation of neighboring molecules. This study is the first step to systematically investigate the optical properties of chlorophyll aggregates, to unveil the supramolecular organization, and to correctly describe the energy transport processes.
Article
Chlorosomes are one of the most unique natural light-harvesting antennas and their supramolecular nanostructures are still under debate. Chlorosomes contain bacteriochlorophyll (BChl)-c, d and e molecules and these pigments self-aggregate under a hydrophobic environment inside a chlorosome. The self-aggregates are mainly constructed by the following three interactions: hydrogen bonding, coordination bonding and π-π stacking. Supramolecular nanostructures of self-aggregated BChls have been widely investigated by spectroscopic and microscopic techniques. Model compounds of such chlorosomal BChl molecules have been synthesized and the effects of esterified long alkyl chains at the 17-propionate residue for their self-aggregation have been studied. Structurally simple zinc chlorophyll derivatives possessing an oligomethylene chain as the esterifying group at the 17-propionate residue were prepared as chlorosomal BChl models. The synthetic zinc BChls self-aggregated in nonpolar organic solvents to give precipitates. The resulting insoluble self-aggregated solids were investigated on a variety of substrates, including hydrophobic, neutral and hydrophilic substrates, by visible absorption, circular dichroism and polarized light absorption spectroscopies, as well as atomic force, transmission electron and scanning electron microscopies. The self-aggregates of synthetic Zn-BChls formed rods with an approximately 5 nm diameter and wires with further elongated growth of the rods (aspect ratio >200). The diameter size was consistent with that estimated for natural chlorosomal rods in a filamentous anoxygenic phototroph, Chloroflexus aurantiacus. The supramolecular formation and stability of the rod on the examined substrates depended on the length of an oligomethylene chain at the 17-propionate residue as well as on the surface properties. Especially, the number of the 5 nm rods on the substrates increased with an elongation of the chain.
Article
1. Fine-scale physical and chemical gradients and deep photosynthetic microbial populations were assessed to provide an initial characterisation of a small, thermally stratified reservoir (Cross Reservoir, Kansas, U.S.A.) and its deep chlorophyll maxima (DCM). Factors were identified that may affect vertical positioning of subepilimnetic photosynthetic sulphur bacteria (PSB) in lakes. 2. Results indicate that Cross Reservoir is a mesotrophic, dimictic lake with large subepilimnetic chlorophyll maxima containing dense layers of PSB. Characteristics of the deep PSB community of Cross Reservoir strongly correlate with both light and nutrient gradients. 3. The deep bacterial community mostly contained single-celled and aggregating green sulphur bacteria, specifically free-living Chlorobium limicola and the conspicuous motile ectosymbiotic consortium known as ‘Chlorochromatium aggregatum’. The bacteria were within the anaerobic hypolimnion, beneath a metalimnetic plate of Cryptomonas spp. and within very low sulphide and light conditions [mean of 67 μgS L−1 and 0.05% photosynthetically active radiation (PAR)]. Pigment concentrations and fluorescence trends indicate that the bacteria made up a larger proportion of the DCM biomass than did phytoplankton in 1996. 4. Cross Reservoir shares characteristics with natural lakes world-wide that also include a deep PSB community containing dense layers of ‘C. aggregatum’. Correlation analyses indicate that PSB community positioning and density are related to light, sulphide supply, redox potentials and pH. A 2-factor principal components analysis (PCA) and other data trends supported these interpretations and indicated that PSB are sensitive to the thermal stability of the water column, are nitrogen limited and regulated more by sulphide or sulphide to light ratios than local levels of light. The sensitivity of these deep photosynthetic bacteria to environmental gradients, and their significance to some aquatic systems, demonstrate their potential as indicators of environmental disturbance.
Article
1Evidence is presented that the ATPase activity detected in cell extracts of Chlorobium thiosulfatophilum is bound to the cytoplasmic membrane rather than to the chlorobium vesicles.2The activity of this ATPase is inhibited in vitro by various carbodiimides, phloridzin and sodium azide.3The apparent Km for ATP is ∼ 0.2 mM and the enzyme shows product inhibition by ADP.4Photophosphorylation, characterized in vivo, is inhibited by many of the compounds that in hibit the ATPase.
Article
Bacteriochlorophyll(BChl)s-c were extracted, isolated and purified from cultured cells of a green photosynthetic bacterium, Chloroflexus (Cfl.) aurantiacus. Their self-aggregates were prepared from a hydrophobic hexane-based solution and the obtained self-aggregate solids were examined by electronic absorption and circular dichroism (CD) spectroscopy as well as atomic force microscopy (AFM). Visible/near-infrared absorption and CD spectra of the BChl-c self-aggregates were very similar to those in cells of Cfl. aurantiacus. AFM analysis indicated that some self-aggregates had rods with a 5-nm diameter and a 3.5-mu m length at longest. The rod diameter was identical to that reported for natural chlorosomal rods of Cfl. aurantiacus. Rod self-aggregates of naturally occurring BChls-c with a 5-nm diameter were first reconstructed here in vitro.
Chapter
The unique physiological characteristic of the photosynthetic bacteria is their ability to grow anaerobically in the light, a property conferred on them by their photosynthetic pigment system. Bacterial processes generally require an exogenous reductant. The different genera of photosynthetic bacteria characteristically use reduced inorganic sulfur compounds, hydrogen, or organic substrates as reductant and also vary with respect to their ability to use carbon dioxide as sole carbon source. This chapter describes the organized structure of photosynthetic apparatus of bacterial system. It describes the structure and location of chromatophore material, isolation and composition of purified chromatophores, and formation of the photosynthetic apparatus. Bacteria like other photosynthetic forms of life have both carotenoids and chlorophylls. Carotenoids essentially harvest light at wavelengths, which are not absorbed by chlorophyll and also protect cells from photodynamic oxidation reactions. Bacteriochlorophyll a is the most widely distributed type of chlorophyll recognized in photosynthetic bacteria. Chromatophores represent a specialized structure that essentially houses the photosynthetic pigments and catalyzes photophosphorylation and photoreduction reactions.
Article
Advances in imaging technologies have revealed that many bacteria possess organelles with a proteomically defined lumen and a macromolecular boundary. Some are bound by a lipid bilayer (such as thylakoids, magnetosomes and anammoxosomes), whereas others are defined by a lipid monolayer (such as lipid bodies), a proteinaceous coat (such as carboxysomes) or have a phase-defined boundary (such as nucleolus-like compartments). These diverse organelles have various metabolic and physiological functions, facilitating adaptation to different environments and driving the evolution of cellular complexity. This Review highlights that, despite the diversity of reported organelles, some unifying concepts underlie their formation, structure and function. Bacteria have fundamental mechanisms of organelle formation, through which conserved processes can form distinct organelles in different species depending on the proteins recruited to the luminal space and the boundary of the organelle. These complex subcellular compartments provide evolutionary advantages as well as enabling metabolic specialization, biogeochemical processes and biotechnological advances. Growing evidence suggests that the presence of organelles is the rule, rather than the exception, in bacterial cells. Advances in imaging techniques have revealed an unexpected abundance and diversity of organelles in bacteria. In this Review, Greening and Lithgow outline the different types of bacterial organelles and discuss common themes in their formation and function.
Chapter
In the beginning of the nineteenth century, de Saussure established that, for the formation of organic matter by green plants in the light, the amount of carbon dioxide assimilated was stoichiometrically related to the amount of cell material formed and molecular oxygen liberated. Since cell material was more reduced than carbon dioxide, it was generally believed that the oxygen produced originated from carbon dioxide. It was Ingenhousz who had shown in 1779 that only the green-pigmented parts, and not the colorless parts of the plants nor the animals, were capable of oxygen production in the light (Rabinowitch, 1945). We can understand, therefore, that the three characteristics of green color, carbon dioxide assimilation, and oxygen evolution conceptually became the fundamental properties of photoautotrophic organisms for the following 130 years.
Article
The fine structure of the cell wall and the process of cell division were examined in thin sections of two unicellular blue-green algae grown under defined conditions. Unilateral invagination of the photosynthetic lamellae is the first sign of cell division in the rod-shaped organism, Anacystis nidulans. Symmetrical invagination of the cytoplasmic membrane and inner wall layers follows. One wall layer, which appears to be the mucopolymer layer, is then differentially synthesized to form the septum; the outer wall layers are not involved in septum formation. Centripetal splitting of the inner layer separates the two daughter cells. A second division, in a plane parallel to the first, usually occurs before the first daughter cells are separated. In the coccoid organism, Gleocapsa alpicola, the features of cell division are broadly similar; however, unilateral invagination of the lamellae is not observed and the second division takes place in a plane perpendicular to the plane of the previous division.
Article
Full-text available
Background Endolithic microbes in coral skeletons are known to be a nutrient source for the coral host. In addition to aerobic endolithic algae and Cyanobacteria, which are usually described in the various corals and form a green layer beneath coral tissues, the anaerobic photoautotrophic green sulfur bacteria (GSB) Prosthecochloris is dominant in the skeleton of Isopora palifera. However, due to inherent challenges in studying anaerobic microbes in coral skeleton, the reason for its niche preference and function are largely unknown. Results This study characterized a diverse and dynamic community of endolithic microbes shaped by the availability of light and oxygen. In addition, anaerobic bacteria isolated from the coral skeleton were cultured for the first time to experimentally clarify the role of these GSB. This characterization includes GSB’s abundance, genetic and genomic profiles, organelle structure, and specific metabolic functions and activity. Our results explain the advantages endolithic GSB receive from living in coral skeletons, the potential metabolic role of a clade of coral-associated Prosthecochloris (CAP) in the skeleton, and the nitrogen fixation ability of CAP. Conclusion We suggest that the endolithic microbial community in coral skeletons is diverse and dynamic and that light and oxygen are two crucial factors for shaping it. This study is the first to demonstrate the ability of nitrogen uptake by specific coral-associated endolithic bacteria and shed light on the role of endolithic bacteria in coral skeletons. Electronic supplementary material The online version of this article (10.1186/s40168-018-0616-z) contains supplementary material, which is available to authorized users.
Article
Chlorosomes are unique light-harvesting apparatuses in photosynthetic green bacteria. Single chlorosomes contain a large number of bacteriochlorophyll(BChl)-c, d, e, and f molecules which self-assemble without protein assistance. These BChl self-assemblies using specific intermolecular interaction (Mg···O3²-H···O=C13¹ and - stacks of chlorin skeletons) in a chlorosome have been reported to be round-shaped rods (or tubes) with a 5-nm or 10-nm diameters, or lamellae with an approximately 2-nm layer spacing. In this study, we report the self-assemblies of synthetic zinc BChl-d analogs possessing ester, amide, and urea groups in the 17-substituent. Spectroscopic analyses indicated that the zinc BChl-d analogs self-assembled in a non-polar organic solvent similarly as in natural chlorosomal BChls with additional assistance by hydrogen-bonding of secondary amide (or urea) groups (CON-H···O=CNH). Microscopic analyses of the supramolecules of a zinc BChl-d analog possessing amide and urea groups showed round- or square-shaped rods with a ~65-nm width. A cryogenic transmission electron microscope showed a lamellar arrangement of the zinc chlorin with the layer spacing of 1.5 nm inside the rod. Similar thick rods were also visible in the microscopic images of self-assemblies of zinc BChl-d analogs possessing one or two secondary amide moieties in the 17-substituent.
Chapter
Among the most significant conceptual advances in biology made in the twentieth century was the realization that sharp discontinuities exist, on the one hand, between cellular organisms and the noncellular entities now known as viruses and, on the other hand, between those cellular organisms that are prokaryotic and those that are eukaryotic in organization of their cells. It may seem strange to a contemporary microbiologist that nonrecognition of these discontinuities, and of the related distinctions among these kinds of life forms, persisted as long as it did. In fact, manifestations of this ignorance were still with us into the 1970s when a number of plant diseases, thought for a century to be caused by filterable viruses, were first shown actually to be caused by various deformable (and, hence, filterable) bacteria without cell walls, the mycoplasma-like entities (Whitcomb and Tully, 1979; this Handbook, Chapters 167 and 169).
Chapter
Among eukaryotes the cyclic respiratory processes just described occur for the greater part in an organelle of the cytoplasm known as the mitochondrion, while glycolysis and related activities are confined to the cytoplasm. In the prokaryotes mitochondria are absent, but many types of those organisms possess a membranous body in which the citric acid cycle may proceed. Because the eukaryotic organelle has been far more extensively explored, its structure receives attention prior to the simpler bodies found in bacteria and their relatives. Although the primary function of the mitochondrion is in cell respiration, it seems to be involved in numerous other aspects of the cell’s economy, as attested by the differing enzyme systems found from tissue to tissue. Most of these roles remain unknown, but some are coming to light at the current time. For instance, in earthworm spermiogenesis it plays an evident part in the condensation of the chromatin in the nucleus (Figure 9.1; Martinucci and Felluga, 1979). Moreover, it has been found to be active in mediating the action of luteinizing hormone in the synthesis of steroids in Amphibia (Wiebe, 1972).
Chapter
The second type of energy-related organelle, the chloroplast, is so closely interwoven with its chief function, photosynthesis, that it is difficult to discuss one without the other. Furthermore, less obvious, but just as real, interrelations exist between this light-dependent production of sugars and other complex series of metabolic events such as glycolysis and photorespiration. Consequently, this organelle and these processes together provide that basis for the bulk of this chapter, along with less thoroughly explored topics that throw light on the ancestry of the modern organelle and its activities.
Chapter
A time line of important research relating to anoxygenic photosynthetic organisms is presented. The time line includes discoveries of organisms, metabolic capabilities, molecular complexes and genetic systems. It also pinpoints important milestones in our understanding of the structure, function, organization, assembly and regulation of photosynthetic complexes.
Chapter
In 1964 an electron microscope study of thin sections of several strains of green bacteria belonging to the genus Chlorobium revealed that these organisms always contained vesicle-like elements connected with the cytoplasmic membrane. Upon fractionation these elements turned out to be associated with a fraction that contained a very high specific chlorophyll content. These observations led to the assumption that these vesicles were the site of the photosynthetic apparatus of green bacteria Ctohen-Bazire, 1964). In 1980 a structural model of these vesicles, then called chlorosomes, in Chlorobium limicola was proposed, based on freeze-fracture studies (Staehelm et al., 1980). In this study evidence was presented for the occurrence of a crystalline baseplate consisting of BChl a-protein between the BChl c-protein in the chlorosome core and the reaction centres in the cytoplasmic membrane. The observation that the chlorosome contains some BChl a-protein, not identical to that present in the baseplate CBerola and Olson, 1966), ted to a slightly modified model (Fig. 1). The baseplate BChl a-protein from the related bacterium, Prosthecochloris aestuarii, has been crystallized and its structure determined by X-ray techniques at 0.19-nm resolution (Fenna et al., 1974; Tronrud et al., T9S6).
Article
Photosynthesis begins when a network of pigment-protein complexes captures solar energy and transports it to the reaction center, where charge separation occurs. When necessary (under low light conditions), photosynthetic organisms perform this energy transport and charge separation with near unity quantum efficiency. Remarkably, this high efficiency is maintained under physiological conditions, which include thermal fluctuations of the pigment-protein complexes and changing local environments. These conditions introduce multiple types of heterogeneity in the pigment-protein complexes, including structural heterogeneity, energetic heterogeneity, and functional heterogeneity. Understanding how photosynthetic light-harvesting functions in the face of these fluctuations requires understanding this heterogeneity, which, in turn, requires characterization of individual pigment-protein complexes. Single-molecule spectroscopy has the power to probe individual complexes. In this review, we present an overview of the common techniques for single-molecule fluorescence spectroscopy applied to photosynthetic systems and describe selected experiments on these systems. We discuss how these experiments provide a new understanding of the impact of heterogeneity on light harvesting and thus how these systems are optimized to capture sunlight under physiological conditions.
Chapter
The three bacterial representatives capable of anoxygenic photosynthesis are members of the family Rhodospirillaceae, Chromatiaceae and Chlorobiaceae (10). Although there are many physiological and anatomical distinctions characterizing each of the families, a major distinction is that the former two families have both their light-harvesting (LH) and reaction-center (RC) activities within the same membrane system (9), whereas members of the Chlorobiaceae have structurally separated these activities (3). Many representatives of the Rhodospirillaceae in addition to growing photoheterotrophically are capable of chemotrophic growth. On the other hand, the Chromatiaceae and Chlorobiaceae are, by and large photoautotrophs (9). Generally, these organisms require a simple salts medium supplemented with a few common B-vitamins. Finally, the purple bacteria, Rhodospirillaceae and Chromatiaceae contain either bacteriochlorophylls (Bchl) a or b (11) (some Bchla containing species have 5% Bchlb:6), while members of the Chlorobiaceae contain in addition to Bchla, Bchl’s c, d or e (7).
Chapter
This chapter discusses the growth of phototrophic bacteria and blue–green algae. The considerable amount of physiological and biochemical work employing blue–green algae involves a few species. Anabaena variabilis, Anabaena cylindrica, Anacystis nidulans, Nostoc muscorum, and Tolypothrix tenuis are some whose relatively rapid growth rate and ease of cultivation permit convenient biochemical examination. Macroscopic growth of blue–green colonies may sometimes be seen in streams and ponds as well as on soil surface, old brickwork, and concrete guttering. The chapter describes some general media that are suitable for several species of Myxophyceae. It discusses some of the special media suitable for a particular species, or group of species. The major variable open to studies on blue–green algae nutrition is the supply of nitrogen. Nitrogen may be supplied as nitrate, nitrite, or ammonia and the presence of such ions in the medium prevents nitrogen fixation.
Chapter
As has been described in Chapter 1, the structure of the outer layers of Grampositive bacteria is reasonably simple as far as can be seen by present techniques. They consist of walls of variable, but always considerable, thickness and of no very clearly defined internal structure. In some species, these walls may bear on their outer surfaces patterned layers of protein which are easily removed, each unit of which consists of a number of sub-units. Underlying the wall and probably physically anchored to it, is the cytoplasmic membrane. This may be invaginated at a limited number of places to form the mesosomes. These sacs or goblets are filled with membranous tubules which are extruded between the wall and membrane when the bacteria are placed in hypertonic solutions. Gram-negative cells, on the other hand, differ considerably in the complexity of their envelopes. Several layers and two membranes are present and the mesosomal membranes are usually less well developed. Among such bacteria are those more specialized micro-organisms that can fix inorganic nitrogen, photosynthesize and use such unlikely food as gaseous H2 and methane. In these groups well developed membrane systems are present, often as packed lamellae or vesicles. Mutants of very common Gram-negative bacteria such as Escherichia coli have also been isolated that under appropriate conditions, seem to accumulate large amounts of extra internal membrane.
Chapter
Earlier reviews in this series primarily discussed electron transport processes in photosynthesis. This is an area of study where rapid progress has occurred during the last 10 or 20 years, and significant advances have again been made since the previous review was written. One area that has been extensively studied in recent years concerns the mechanism of oxygen evolution, a subject that was also discussed at some length 2 years ago (AMESZ 1983). For the first time, evidence is now available concerning the chemical identity of the electron carrier Z that connects the oxygen-evolving complex with the primary electron donor of photosystem II (DEKKER et al. 1984a, O’MALLEY and BABCOCK 1984, DINER and DeVITRY 1984). Moreover, direct evidence has been obtained that manganese functions as the redox center for the oxygen evolving complex (DEKKER et al. 1984b,c, see also DISMUKES and SIDERER 1981) and insight in the roles of Ca2+ and C1- ions and of some of the peptides that are part of the photosystem II complex in oxygen evolution is emerging now (see Sect. 3a).
Chapter
By nature, humans are inquisitive animals: this is the foundation of scientific investigation. However, we sometimes have difficulty in comprehending, and therefore interpreting, the data; this is especially true when working with systems much different from those of our own experience. In these cases, we are forced to attempt to comprehend the system by the use of analogy. For example, when describing the nature of fundamental quark particles, nuclear physicists have allocated to them the characteristics of flavor and color. These words are used because different flavors or kinds of quarks exist, and all possess one of three colors that combine in quantum mechanics reminiscent of the way visual colors coalesce. The words color and flavor have nothing whatsoever to do with our visible and tangible world, but the analogy makes it easier to understand. Analogies are advantageous, as they make difficult concepts simpler by equating them with the experience of our everyday life. However, we must also realize that they may make our interpretation too shallow for those uncertain worlds beyond our total grasp.
Chapter
Phototrophic bacteria, including oxygenic and anoxygenic phototrophic bacteria, can transform light energy into metabolically useful chemical energy by chlorophyll- or bacteriochlorophyll-mediated processes. Major differences between oxygenic and anoxygenic phototrophic bacteria relate to their photosynthetic pigments and the structure and complexity of the photosynthetic apparatus (Stanier et al., 1981). Photosynthesis in anoxygenic phototrophic bacteria depends on oxygen-deficient conditions, because synthesis of the photosynthetic pigments is repressed by oxygen (bacteria like Erythrobacter longus are exceptions to this rule); in contrast to photosynthesis in plants and cyanobacteria (including Prochloron and related forms), oxygen is not produced. Unlike the cyanobacteria and eukaryotic algae, anoxygenic phototrophic bacteria are unable to use water as an electron donor. Most characteristically, sulfide and other reduced sulfur compounds, but also hydrogen and a number of small organic molecules, are used as photosynthetic electron donors. [Anoxygenic photosynthesis with sulfide, an inhibitor of photosystem II, as electron donor is also carried out by some cyanobacteria using photosystem I only (Cohen et al., 1975; Garlick et al., 1977).] As a consequence, the ecological niches of anoxygenic phototrophic bacteria are anoxic parts of waters and sediments, which receive light of sufficient quantity and quality to allow phototrophic development. Representatives of this group are widely distributed in nature and found in freshwater, marine, and hypersaline environments, hot springs, and arctic lakes, as well as elsewhere. They live in all kinds of stagnant water bodies, in lakes, waste water ponds, coastal lagoons, stratified lakes, and other aquatic habitats, but also in marine coastal sediments, in moist soils, and in paddy fields.
Article
Since the discovery of the green sulfur bacteria and the first description by Larsen (1952), this group of bacteria has gained much interest because of a number of highly interesting features. These include the unique structures of the photosynthetic apparatus and the presence of small organelles, the chlorosomes, which act as light-harvesting antenna. Chlorosomes are very powerful light receptors that can capture minute amounts of light and enable the green sulfur bacteria to perform photosynthesis and to grow at very low-light intensities. This has important ecological consequences, because the efficient light harvesting determines the ecological niche of these bacteria at the lowermost part of stratified environments, where the least of light is available. Furthermore, the strict dependency on photosynthesis to provide energy for growth and the obligate phototrophy of the green sulfur bacteria together with their characteristic sulfur metabolism has provoked much interest in their physiology, ecology, and genomics. The oxidation of sulfide as the outmost important photosynthetic electron donor of the green sulfur bacteria involves the deposition of elemental sulfur globules outside the cells and separates the process of sulfide oxidation to sulfate clearly into two steps. In the phylogenetic-based taxonomy, the green sulfur bacteria are treated as family Chlorobiaceae with the genera Chlorobium, Chlorobaculum, Prosthecochloris, and Chloroherpeton.
Article
Bacterial chromatophores exhibit certain biochemical properties similar to those of chloroplasts and are comparable to those of plant or animal mitochondria. For instance, chromatophores carry out cyclic photophosphorylation similar to that of chloroplasts; on the other hand, chromatophores, like mitochondria, catalyze a dark oxidation of certain substrates via an electron carrier system with oxygen as the final electron acceptor, and this oxidation may be accompanied by phosphorylation. Chromatophores present an unusual combination of metabolic systems present in chloroplasts and mitochondria of higher organisms. When a strain of photosynthetic bacteria is cultured under a variety of environmental conditions, changes in the yield of chromatophores, their pigment content, and other biochemical changes may be detected. The procedures employed for the isolation and fractionation of chromatophores from photosynthetic bacteria fall into two groups: (1) mechanical rupture of cells and dispersal of cell contents by sonic oscillation, or by the French pressure cell, or by grinding with alumina and (2) enzymatic disruption of cell walls formation of spheroplasts, followed by osmotic lysis or mild homogenization.
Article
Four taxonomic groups of classical prokaryotes and one group of archaebacteria (Woese, Magrum, and Fox, 1978) can convert light energy into chemical-bond energy. They belong to three functional categories, in terms of the photochemical mechanisms involved (Table 1).
Article
The ubiquity of cell membranes and cell surface structures has long been recognized as an essential element of cellular structure and function. Thus a surface membrane or envelope provides the cell with the necessary protective barrier which enables it to regulate the biochemical processes needed for biosynthesis, cell growth, and energy metabolism. Indeed, in the earliest microscopic studies of Anton van Leeuwenhoek the existence of a surface film or layer which held the “animalcules” together was anticipated. One almost senses Leeuwenhoek’s feeling of surprise when he recorded that he was unable to “discern any film” which “contained” these “clear globules” (i.e., bacteria) resolved under his primitive microscope. The concept of the structural and functional reality of cell membranes was given much substance by the early work of Gorter and Grendel (1925) and Danielli and Dayson (1935). These pioneers of the modern work on cell membranes established that biological membranes were essentially lipid—protein structures, and, moreover, a rather specific type of molecular architecture in the form of the bimolecular leaflet or sandwich structure was assigned to the membrane (Danielli and Dayson, 1935). Electron microscopy of thin sections of fixed, stained cells of various origins led Robertson (1959) to suggest the universality of the “unit” double-track membrane for all cells. The alternate electron dense—light-dense layering of the membrane profiles provided remarkable visual evidence which supported the molecular organization implicit in the Danielli—Dayson model.
Article
Chlorosomes are major light-harvesting antenna apparatuses in green photosynthetic bacteria. Chlorosomes contain a large amount of bacteriochlorophyll(BChl)-c, d, e and f molecules and the supramolecular nanostructures of their self-assemblies are suggested to be rods with 5-nm or 10-nm diameters and/or lamellas with approximately 2-nm spacing. BChls-c were extracted, isolated and purified from cultured cells of a green sulfur photosynthetic bacterium, Chlorobaculum (Cba.) tepidum. Self-assemblies of the natural composite BChls-c as well as each pure homolog/epimer were prepared in a hydrophobic hexane-based solution and the resulting self-assembled solids were investigated by spectroscopic and microscopic techniques. Visible and near-infrared absorption and circular dichroism spectra of the in vitro self-assemblies of the natural composite BChls-c on a quartz substrate were closely similar to those in cells of Cba. tepidum in an aqueous buffer solution. Self-assemblies of (31 R)-epimerically pure BChl-c molecules showed a wider Qy absorption band with increase in the steric bulkiness of hydrocarbon substituents at the 8- and 12-positions, which were effective for capturing wider wavelength light. (31 S)-BChls-c gave similar self-assembly bands, but more monomeric and/or dimeric species than (31 R)-BChls-c. Atomic force microscopic images of in vitro self-assemblies of natural composite BChls-c showed a rod with a 5-nm height and bundles of fibrils with 1-2-nm heights. Spectroscopic and microscopic analysis suggested that the 82-methylation enhanced π-π stacking of self-assemblies by hydrophobic interaction, but the 121-methylation slightly weakened the intermolecular interactions due to its steric bulkiness.
Chapter
This chapter discusses centrifugal techniques for the isolation and characterization of subcellular components from bacteria. Centrifugal procedures are applied early in many microbiological investigations. For small volumes of culture fluid the micro-organisms may be harvested in a single batch process in a variety of swing-out or fixed-angle rotors. The majority of manufacturers of centrifuge equipment produce instruments operating at controlled temperatures with rotors of this capacity and capable of developing the necessary gravitational fields to sediment most micro-organisms. For larger volumes of culture fluid, a continuous flow rotor is to be preferred. Such rotors may be of the cream-separator type or a rotor designed or modified for continuous operation in a conventional laboratory centrifuge. In both continuous and batch harvesting, although the fields applied will theoretically sediment all of the organisms from the culture, the yield of cells is sometimes sacrificed to speed the harvest. Developments in the theory of sedimentation and the design of rotors, cells, and accessories have permitted the full exploitation of three basic physical parameters of biological objects to separate and characterize them by the application of centrifugal force. Separations may be achieved (1) on the basis of their size and shape, (2) by their density differences, or (3) by their mass differences.
Article
Membrane fragments of Heliobacillus (Hc.) mobilis were characterized using resonance Raman (RR) spectroscopy in order to determine the configuration of the neurosporene carotenoid, the pigment-protein interactions of the bacteriochlorophyll (BChl) g molecules, and the Chl a-like chlorin pigments present in the antenna-reaction center complex constituting the photosynthetic apparatus. Using 363.8 nm excitation, the Raman contributions of the BChl g molecules were selectively resonantly enhanced over those of the carotenoid and the Chl a-like chlorin pigments. The RR spectrum of BChl g in these membranes excited at 363.8 nm exhibits bands at 1614 and 1688 cm−1, which correspond to a CaCm methine bridge stretching mode and a keto carbonyl group stretching mode, respectively. Both of these bands are 16 cm−1 wide (full width at half maximum, FWHM), indicating that a sole population of BChl g molecules is being enhanced at this excitation wavelength. The observed frequency of the CaCm stretching mode (1614 cm−1) indicates that the bulk of BChl g molecules is pentacoordinated with only one axial ligand to the central Mg atom while that of the keto carbonyl stretching mode (1668 cm−1) indicates that these groups are engaged in a hydrogen bond. This homogeneous population of BChl g molecules bound to the heliobacterial core polypeptides is in contrast to the heterogeneous population of Chl a molecules bound to the core polypeptides of the reaction center of photosystem I of Synechocystis 6803 as observed by the inhomogeneously broadened C9 keto carbonyl band in its RR spectrum. The RR spectrum of the Chl a-like chlorin pigments in Hc. mobilis excited at 441.6 nm exhibits a broad keto carbonyl band (43 cm−1 FWHM) with components at 1665, 1683 and 1695 cm−1, indicating several populations of these pigments differing in their protein interactions at the level of the keto carbonyl group. Fourier transform (FT) pre-RR spectroscopic measurements of intact whole cells and membrane fragments at room temperature using 1064 nm excitation indicate that high quality vibrational spectra of the BChl g molecules can be obtained with no photodegradation. Low-temperature FT Raman spectra excited at 1064 nm reveals an inhomogeneously broadened 1665 cm−1 band corresponding to the C9 keto carbonyl stretching mode. Spectral deconvolution and second derivative analysis of this band reveal that it is comprised of components at 1665, 1682 and 1695 cm−1, the latter two most likely arising from BChl g photoconversion products. Excitation using 885 nm to enhance the preresonance effect of the BChl g molecules yields an FT Raman spectrum where the keto carbonyl band at 1665 cm−1 is narrow, as is the case in the Soret RR spectra, reflecting a sole population of BChl g molecules, which are engaged in an H bond. The RR spectrum of the neurosporene molecule in Hc. mobilis membranes excited at 496.5 nm is compared to that of 1,2-dihydroneurosporene bound in a cis configuration in reaction centers of Rhodopseudomona viridis and to that of the same carotenoid in its all-trans configuration extracted from these reaction centers in the presence of light. The similarity of this latter RR spectrum with that of neurosporene in the Hc. mobilis membranes indicates that it is bound in an all-trans configuration.
  • C B Van Niel
VAN NIEL, C. B., Arch. Mikrobiol., 1932, 3, 1.
  • V N Kondrat 'eva
SHAPOSHNIKOV, V. N., KONDRAT'EVA, E. N., and FEOOROV, V. D., Nature, 1960, 187,167.
  • H E Zubay
HUXLEY, H. E., and ZUBAy, G., J. Mol. Biol., 1960, 2, 10.
  • A M Hopwood
GLAUERT, A. M., and HoPwooD, D., J. BiG physic. and Biochem. Cytol., 1959, 6, 515.
  • W Van Iteason
VAN ITEaSON, W., J. Biophysic. and Biochern. Cytol., 1961, 9, 183.
  • P Daews
GIESBRECHT, P., and DaEws, G., Arch. Mikrobiol., 1962, 43, 152.
  • A Ryter
  • Kellenbf Rger
RYTER, A., and KELLENBF.RGER, E., Z. Naturforsch., 1958, 13b, 597.
  • G Millonm
MILLONm, G., J. Biophysic. and Biochem. Cytol., 1961, 11,736.
  • R Y Stanier
STANIER, R. Y., and SMITH, J. H. C., Biochim. et Biophysica Acta, 1960, 41,478.
  • V N Shaposhnikov
  • E N Kondrat'eva
SHAPOSHNIKOV, V. N., KONDRAT'EVA, E. N., and FEOOROV, V. D., Nature, 1960, 187,167.
  • E G Prinosheim
PRINOSHEIM, E. G., Arch. Mikrobiol., 1953, 19,353.
  • N Pfennig
PFENNIG, N., Naturwissenschaften, 1961, 48, 136.
  • H E Huxley
  • G Zubay
HUXLEY, H. E., and ZUBAy, G., J. Mol. Biol., 1960, 2, 10.
  • A Layne
LAYNE, A., in Methods in Enzymology, (S. P. Colowick and N. O. Kaplan, editors), New York, Academic Press, Inc., 1957, 3,448.
  • P C Fitz-James
FITZ-JAMES, P. C., J. Biophysic. and Biochem. Cytol., 1960, 8,507.
  • A M Glauert
  • D Hopwood
GLAUERT, A. M., and HoPwooD, D., J. BiG physic. and Biochem. Cytol., 1959, 6, 515.
  • P Giesbrecht
  • G Daews
GIESBRECHT, P., and DaEws, G., Arch. Mikrobiol., 1962, 43, 152.