[show abstract][hide abstract] ABSTRACT: This work characterizes a unicellular cyanobacterium with nearly spherical cells and thin outlined sheaths that divide irregularly forming small packets immersed in a diffluent mucilaginous layer. It was isolated growing on calcite speleothems and walls in a show cave in Collbató (Barcelona, Spain). Spectral confocal laser and transmission electron microscopies were used to describe the morphology, the fine structure and the thylakoid arrangement. The pigments identified were phycoerytrin, phycocyanin, allophycocyanin and chlorophyll a. The three-dimensional reconstructions, generated from the natural fluorescence z-stacks, evidenced a large surface area of nearly flat arm-like thylakoidal membranes connected to each other and forming a unified structure in a way that has never been described before. Phylogenetic analyses showed 95% homology to the strain Chroococcus sp. JJCM (AM710384). The phenotypic diacritic features do not correspond to any species currently described and the genetic traits support it being classified as an independent genus in the order Chroococcales and the family Chroococcaceae. Hence, we propose the name Chalicogloea cavernicola gen. nov. sp. nov. The type strain is Chalicogloea cavernicola-COLL 3T (=CCALA 975 T = CCAP 1424/1 T).
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 11/2012; · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: Surfaces of buildings at the archaeological site of Palenque, Mexico, are colonized by cyanobacteria that form biofilms, which in turn cause aesthetic and structural damage. The structural characterization and species composition of biofilms from the walls of one of these buildings, El Palacio, are reported. The distribution of photosynthetic microorganisms in the biofilms, their relationship with the colonized substratum, and the three-dimensional structure of the biofilms were studied by image analysis. The differences between local seasonal microenvironments at the Palenque site, the bioreceptivity of stone and the relationship between biofilms and their substrata are described. The implications for the development and permanence of species capable of withstanding temporal heterogeneity in and on El Palacio, mainly due to alternating wet and dry seasons, are discussed. Knowledge on how different biofilms contribute to biodegradation or bioprotection of the substratum can be used to develop maintenance and conservation protocols for cultural heritage.
[show abstract][hide abstract] ABSTRACT: Caves with dim natural light, and lighted hypogean environments, have been found to host phototrophic microorganisms from varioustaxonomic groups. These microorganisms group themselves into assemblies known as communities or biofilms, which are associated withrock surfaces. In this work, the phototrophic biofilms that colonise speleothems, walls and floors in three tourist caves (Spain) were studied.Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to study these organisms and acquirethree-dimensional data on their biofilm structure. CLSM was used in a multi-channel mode whereby the different channels map individualbiofilm components. Cyanobacteria, green microalgae, diatoms, mosses and lichens were found to be grouped as biofilms that differedaccording to the sampling sites. The biofilms were classified into six types regarding their environmental conditions. These types weredefined by their constituent organisms, the thickness of their photosynthetic layers and their structure. Light-related stress is associated with lower biofilm thickness and species diversity, as is low humidity, and, in the case of artificially illuminated areas, the duration of lightexposure.
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to evaluate the potential of green light (GL) for preventing biofilm growth in areas of cultural patrimony, which are normally illuminated with artificial white light (WL). The aerophytic cyanobacterium Gloeocapsopsis magma, colonizer of caves, was cultured under either GL or WL and its morphology and ultrastructure were compared. Spectral analysis of pigments showed high levels of phycoerythrin. GL light quality affected the morphology of colonies, thickness and organization of the sheath, cell size and formation of storage products. At the fine structure level the number of thylakoids was significantly decreased, compared to WL grown cells. Cells from two-months and sixmonths old WL cultures did not differ either in the number or disposition of their thylakoids. Although G. magma exposed to GL survived in nature and in culture the unbalanced fine structure reveals the limits of its adaptation.
[show abstract][hide abstract] ABSTRACT: Artificial illumination can harm works of art by inducing the development of photosynthetic biofilms. With the aim of preventing biodeterioration or esthetic damage to such surfaces, we evaluated and compared the effects of illuminating biofilms formed by Gloeothece membranacea (cyanobacteria) and Chlorella sorokiniana (Chlorophyta) using exclusively white or green light.
Applied and Environmental Microbiology 05/2006; 72(4):3026-31. · 3.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: A new imaging technique for the analysis of fluorescent pigments from a single cell is reported. It is based on confocal scanning laser microscopy coupled with spectrofluorometric methods. The setup allows simultaneous establishment of the relationships among pigment analysis in vivo, morphology, and three-dimensional localization inside thick intact microbial assemblages.
Applied and Environmental Microbiology 07/2004; 70(6):3745-50. · 3.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: The distribution of biofilms, the diversity of phototrophic organisms, and their relation to environmental conditions were studied in three limestone cavities in the karstic Garraf massif (Barcelona, NE Spain). Sixty-two taxa: 28 Cyanobacteria (42.8% Chroococcales, 21.4% Oscillatoriales, 7.1% Nostocales and 28.6% Stigonematales), 11 Chlorophyta, 16 Bacillariophyta and 7 lichens were identified. The environmental data obtained at three cavities by measuring temperature, relative humidity and light, showed a clear gradient from the entrance to a certain depth beyond which they remained stable. In a broad sense, the existence of three different levels can be assumed: a) Entrance level. The microclimate was strongly influenced by the outdoors. Scarcely attenuated light and abiotic factors fluctuated throughout the year. On the highly illuminated dry rocks the microflora colonies were quite rich, with special abundance of mucilaginous biofilms composed of algae and cyanobacteria typical of terrestrial aerophytic or atmophytic habitats. The community dominated by Scytonema julianum thrived in areas protected from rain. Trentepohlia sp. and many crustose lichens, which had this alga as a photobiont, were abundant. b) Intermediate level, with moderate abiotic oscillations and low light (25-0.5 mV) that was not yet a stress factor.A mixture of species formed biofilms. Cyanobacteria were their most visible constituents, occasionally mixed with green algae and diatoms. Biofilm abundance diminished with decreasing irradiance. c) Deep level (< 1 mV) until light extinction, with stable abiotic factors (10°C and dew point humidity). Only a few species were able to colonize this dim light zone. The presence of remains and empty sheaths increased with decreasing irradiance, and except for Geitleria calcarea and Loriella osteophila, the algae were heavily colonized by bacteria and filamentous fungi.
Nova Hedwigia 04/2004; 78(3-4):329-351. · 0.81 Impact Factor
[show abstract][hide abstract] ABSTRACT: Confocal Laser Scanning Microscopy (CLSM) was used to investigate aerophytic phototrophic biofilms thriving on artificially illuminated surfaces in Roman hypogean monuments, particularly the St. Callistus and Domitilla Catacombs (Rome, Italy). Phototrophic organisms were visualized by their in vivo pigment fluorescence, whereas extrapolymeric substances (EPS) and DNA structures of both photo- and heterotrophic microorganisms were revealed respectively with the carbohydrate recognising lectin Concanavalin-A conjugated with the fluorophore Alexa Fluor 488 and the fluorochrome Hoechst 33258 labels. Inherent fluorescences other than pigment fluorescence such as CaCO3 fluorescence of the substratum were also detected. Distribution of microorganisms and EPS in biofilms and their relationship with substratum was evidenced with the application of diverse kinds of image analyses. Detailed localization of certain structures or taxa was achieved with the examination of gallery images. On the other hand, particular image analyses enlightened one or several partial aspects of the biofilm heterogeneity. Extended focus images built with the maximum intensity projections of the x-y, x-z, and y-z planes were best to compare among biofilms and to reveal their porosity and stratification. 3D-reconstructions of biofilms as perspective images gave an account of the surface characteristics such as roughness or coverage of the substratum surface. Topographic reconstruction was used to measure geometrical and biological heterogeneity parameters like sample thickness or surface roughness. What makes CLSM so powerful is the ability to analyse samples with minimal preparation and non-disturbing architectural observation, the use of multiple excitation and detection wavelengths at different depths of focus, and the large pool of digital image processing algorithms with which one can effectively target specific elements in the biofilm sample, such as molecules (e.g. DNA and pigments), structure (e.g. surfaces, matrix, sheaths and filaments) and properties (e.g. stage of cell division, growth and senescence), with the capability to fully visualise them all in 3D image.
[show abstract][hide abstract] ABSTRACT: Organisms building biofilms are of considerable interest in the context of degradation of cultural heritage. Particularly, hypogean environments exposed to artificial light are colonized by microbial communities, which damage walls and frescoes. In order to ascertain the mechanisms by which phototophic biofilms thrive under the particular conditions of hypogea, the organism composition and three-dimensional structure of biofilms from the Roman catacombs St. Callistus and Domitilla were studied. The main phototrophic organisms forming the biofilms were filamentous sheathed cyanobacteria and mosses. Biofilms were spatially very heterogeneous in thickness, density and organism composition but could be classified as regards their main organisms. There was a trend of decreasing diversity in the phototrophic composition of the biofilms under lower irradiances, the one at the lowest irradiance being uniquely built by erected filaments of Leptolyngbya sp. Except for this biofilm, the main organism composition was not clearly related with decreasing irradiance. However, biofilms from dim light samples were porous and the filamentous cyanobacteria in them were erected. Leptolyngbya sp., the most ubiquitous species, displayed a high number of phycobilisomes and its hormogonia a gliding movement that allowed colonization of substrata. Such mechanisms may have an important role for thriving under the low light conditions of the catacombs.