Zdeno Gardian

University of South Bohemia in České Budějovice

Photoheterotrophic bacteria harvest light energy using either proton-pumping rhodopsins or bacteriochlorophyll (BChl)-based photosystems. The bacterium Sphingomonas glacialis AAP5 isolated from the alpine lake Gossenköllesee contains genes for both systems. Here, we show that BChl is expressed between 4°C and 22°C in the dark, whereas xanthorhodops...

Possibly the most abundant group of anoxygenic phototrophs are marine photoheterotrophic Gammaproteobacteria belonging to the NOR5/OM60 clade. As little is known about their photosynthetic apparatus, the photosynthetic complexes from the marine phototrophic bacterium Congregibacter litoralis KT71 were purified and spectroscopically characterised. T...

An aerobic, yellow-pigmented, bacteriochlorophyll a-producing strain, designated AAP5 (=DSM 111157=CCUG 74776), was isolated from the alpine lake Gossenköllesee located in the Tyro-lean Alps, Austria. Here, we report its description and polyphasic characterization. Phylogenetic analysis of the 16S rRNA gene showed that strain AAP5 belongs to the ba...

Photoheterotrophic bacteria represent an important part of aquatic microbial communities. There exist two fundamentally different light-harvesting systems: bacteriochlorophyll-containing reaction centers or rhodopsins. Here, we report a photoheterotrophic Sphingomonas strain isolated from an oligotrophic lake, which contains complete sets of genes...

Photosystem II (PSII) is a large membrane protein complex performing primary charge separation in oxygenic photosynthesis. The biogenesis of PSII is a complicated process that involves a coordinated linking of assembly modules in a precise order. Each such module consists of one large chlorophyll-binding protein, number of small membrane polypeptid...

Pathogenic Bordetella bacteria release a neurotropic dermonecrotic toxin (DNT) that is endocytosed into animal cells and permanently activates the Rho family GTPases by polyamination or deamidation of the glutamine residues in their switch II regions (e.g., Gln63 of RhoA). DNT was found to enable high level colonization of the nasal cavity of pigs...

Survival of phototrophic organisms depends on their ability to collect and convert enough light energy to support their metabolism. Phototrophs can extend their absorption cross section by using diverse pigments and by tuning the properties of these pigments via pigment–pigment and pigment–protein interaction. It is well known that some cyanobacter...

The soil chromophyte alga Xanthonema (X.) debile contains only non-carbonyl carotenoids and Chl-a. X. debile has an antenna system denoted Xanthophyte light-harvesting complex (XLH) that contains the carotenoids diadinoxanthin, heteroxanthin, and vaucheriaxanthin. The XLH pigment stoichiometry was calculated by chromatographic techniques and the pi...

We have used time-resolved absorption and fluorescence spectroscopy with nanosecond resolution to study triplet energy transfer from chlorophylls to carotenoids in a protective process that prevents the formation of reactive singlet oxygen. The light-harvesting complexes studied were isolated from Chromera velia, belonging to a group Alveolata, and...

The majority of life on Earth depends directly or indirectly on the sun as a source of energy. The initial step of photosynthesis is facilitated by light-harvesting complexes, which capture and transfer light energy into the reaction centers (RCs). Here, we analyzed the organization of photosynthetic (PS) complexes in the bacterium G. phototrophica...

Detailed discussion of the BChl a stoichiometry in PS complex. BChl, bacteriochlorophyll; PS, photosynthetic. (DOC)

Flash-induced absorbance spectra of purified photosynthetic complexes of G. phototrophica. As expected for the type 2 RC, the signal is dominated by signatures of the oxidized primary donor (P870+): bleaching around 865 nm, electrochomic shift of the accessory BChl a around 800 nm and bleaching of the Qx band of the primary donor at 600 nm. BChl, b...

Parameters used for computation of the steady-state optical spectra of G. phototrophica PS complex. PS, photosynthetic. (PDF)

Absorption spectra of PS membranes from G. phototrophica (red) and R. rubrum (grey). PS, photosynthetic. (TIF)

Upper panel: size exclusion chromatography of the partially purified PS complexes from G. phototrophica. The blue line recorded at 820 nm shows the fraction with the purified complex, and the red trace at 490 nm represent the carotenoids. Lower panel: the absorption spectrum of the obtained complex (blue) and the spectrum of the “free” carotenoids...

Example of a raw TEM image of G. phototrophica complexes. TEM, transmission electron microscopy. (TIF)

PS complex of G. phototrophica analyzed by native and SDS polyacrylamide gel electrophoresis. (A) Clear-native gel electrophoresis of G. phototrophica membrane complexes in comparison with membrane complexes of R. rubrum and Synechocystis sp. PCC 6803; the membranes were solubilized using 2% dodecyl-β-maltoside and loaded on 4%–14% clear-native gel...

BChl a fluorescence induction and relaxation recorded using the kinetic fluorometer FL-3000 (Photon Systems Instruments Ltd., Brno, Czech Republic). The BChl fluorescence induction transient was elicited by a 140 μs-long square-wave pulse of light with an intensity of approximately 0.1 mol photon m−2s−1 provided by an array of blue-green 505 nm Lux...

Estimated angular distance between neighboring subunits of the PS complex. The angle was measured as shown in the insert. The data were derived from 23 measurements from 4 individual complex images. PS, photosynthetic. (TIF)

The spectro-temporal datasets obtained from the measurements were analyzed globally by fitting package DAFit (Pascher Instruments). To visualize the excited state dynamics, we assumed that the excited states evolved according to a sequential, irreversible scheme A → B, B → C, C → D. The arrows represent increasingly slower processes and the time co...

Comparison of B816 and B868 absorption bands. Red line: absorption spectrum of G. phototrophica PS complex. Grey area: absorption spectrum of R. rubrum complex scaled and blue-shifted to match the B868 band. Blue area: the difference between the red and grey spectra, corresponds to the pure spectrum of the B816 absorption band. The ratio of B816 an...

Photosystem I (PSI) is a multi-subunit integral pigment–protein complex that performs light-driven electron transfer from plastocyanin to ferredoxin in the thylakoid membrane of oxygenic photoautotrophs. In order to achieve the optimal photosynthetic performance under ambient irradiance, the absorption cross section of PSI is extended by means of p...

We present proteomic, spectroscopic, and phylogenetic analysis of light-harvesting protein (Lhc) function in oleaginous Nannochloropsis oceanica (Eustigmatophyta, Stramenopila). N. oceanica utilizes Lhcs of multiple classes: Lhcr-type proteins (related to red algae LHCI), Lhcv (VCP) proteins (violaxanthin-containing Lhcs related to Lhcf/FCP protein...

Formation of the multi-subunit oxygen-evolving Photosystem II (PSII) complex involves a number of auxiliary protein factors. In this study we compared the location and possible function of two homologous PSII assembly factors, Psb28-1 and Psb28-2, from the cyanobacterium Synechocystis sp. PCC 6803. We show that FLAG-tagged Psb28-2 is present in bot...

Spatial segregation of photosystems in the thylakoid membrane (lateral heterogeneity) observed in plants and in the green algae is usually considered to be absent in photoautotrophs possessing secondary plastids, such as diatoms. Contrary to this assumption, here we show that thylakoid membranes in the chloroplast of a marine diatom, Phaeodactylum...

Chlorobaculum tepidum is a representative of green sulfur bacteria, a group of anoxygenic photoautotrophs that employ chlorosomes as the main light-harvesting structures. Chlorosomes are coupled to a ferredoxin-reducing reaction center by means of the Fenna-Matthews-Olson (FMO) protein. While the biochemical properties and physical functioning of a...

The remarkable adaptability of diatoms living in a highly variable environment assures their prominence among marine primary producers. The present study integrates biochemical, biophysical and genomic data to bring new insights into the molecular mechanism of chromatic adaptation of pennate diatoms in model species Phaeodactylum tricornutum, a mar...

The arrangement of core antenna complexes (B808-866-RC) in the cytoplasmic membrane of filamentous phototrophic bacterium Chloroflexus aurantiacus was studied by electron microscopy in cultures from different light conditions. A typical nearest-neighbor center-to-center distance of ~18 nm was found, implying less protein crowding compared to membra...

Fucoxanthin-chlorophyll proteins (FCP) are the major light-harvesting proteins of diatom algae, a major contributor to marine carbon fixation. FCP complexes from representatives of centric (Cyclotella meneghiniana) and pennate (Phaeodactylum tricornutum) diatoms were prepared by sucrose gradient centrifugation and studied by means of electron micro...

A novel chlorophyll a containing pigment protein complex expressed by cells of Chromera velia adapted to growth under red/far red illumination [1]. Purification of the complex was achieved by means of anion-exchange chromatography and gel-filtration. The antenna is shown to be an aggregate of ~20kDa proteins of the LHC family, unstable in the isola...

The structure and composition of the light harvesting complexes from the unicellular alga Chromera velia were studied by means of optical spectroscopy, biochemical and electron microscopy methods. Two different types of antennae systems were identified. One exhibited molecular weight (18-19kDa) similar to FCP (Fucoxanthin Chlorophyll Protein) compl...

Chromophytes are an important group of microorganisms that contribute significantly to the carbon cycle on Earth. Their photosynthetic capacity depends on efficiency of the light-harvesting system that differs in pigment composition from that of green plants and other groups of algae. Here we employ femtosecond transient absorption spectroscopy to...

Photosynthetic carbon fixation by Chromophytes is one of the significant components of a carbon cycle on the Earth. Their photosynthetic apparatus is different in pigment composition from that of green plants and algae. In this work we report structural maps of photosystem I, photosystem II and light harvesting antenna complexes isolated from a soi...

Chlorophyll (Chl) a/b-binding proteins from Prochlorothrix hollandica known as Pcb antennae were studied by femtosecond transient absorption technique to identify energy transfer rates and pathways in Pcb and Pcb-PS I complexes. Carotenoids transfer energy to Chl with low efficiency of approximately 25% in Pcb complexes. Interestingly, analysis of...

The freshwater filamentous green oxyphotobacterium Prochlorothrix hollandica is an unusual oxygenic photoautotrophic cyanobacterium differing from most of the others by the presence of light-harvesting Pcb antenna binding both chlorophylls a and b and by the absence of phycobilins. The pigment-protein complexes of P. hollandica SAG 10.89 (CCAP 1490...

Gun4 is a porphyrin-binding protein that activates magnesium chelatase, a multimeric enzyme catalyzing the first committed step in chlorophyll biosynthesis. In plants, GUN4 has been implicated in plastid-to-nucleus retrograde signaling processes that coordinate both photosystem II and photosystem I nuclear gene expression with chloroplast function....

Structure and organisation of Photosystem I and Photosystem II isolated from red alga Cyanidium caldarium was determined by electron microscopy and single particle image analysis. The overall structure of Photosystem II was found to be similar to that known from cyanobacteria. The location of additional 20 kDa (PsbQ') extrinsic protein that forms p...

In this paper our algorithm, which helps biologists to examine structure of very small objects, is described. These small objects are many times on the display limit of the best existent microscopes and the quality of the raw images is insufficient. In this case is advantageous to use a digital postprocessing of the images. The digital postprocessi...