Molecular Characterization of an Endolithic Microbial Community in Dolomite Rock in the Central Alps (Switzerland)

Endolithic microorganisms colonize the pores in exposed dolomite rocks in the Piora Valley in the Swiss Alps. They appear as distinct grayish-green bands about 1-8mm below the rock surface. Based on environmental small subunit ribosomal RNA gene sequences, a diverse community driven by photosynthesis has been found. Cyanobacteria (57 clones), especially the genus Leptolyngbya, form the functional basis for an endolithic community which contains a wide spectrum of so far not characterized species of chemotrophic Bacteria (64 clones) with mainly Actinobacteria, Alpha-Proteobacteria, Bacteroidetes, and Acidobacteria, as well as a cluster within the Chloroflexaceae. Furthermore, a cluster within the Crenarchaeotes (40 clones) has been detected. Although the eukaryotic diversity was outside the scope of the study, an amoeba (39 clones), and several green algae (51 clones) have been observed. We conclude that the bacterial diversity in this endolithic habitat, especially of chemotrophic, nonpigmented organisms, is considerable and that Archaea are present as wel

Induction of stress proteins in the phototrophic bacterium Rhodobacter sphaeroides

The stress response of the phototrophic bacterium Rhodobacter sphaeroides was investigated by two-dimensional gel electrophoresis. Oxygen, 0.5% and 4% ethanol, UV radiation, heat shock at 42°C and 0.01% phenanthrene were tested as stress factors. The protein pattern on two-dimensional gels of stressed as compared to control cells revealed that all stress factors applied caused modifications in the protein pattern of R. sphaeroides. The intensity of particular spots increased or decreased as a consequence of altered protein synthesis. Specific and general stress responses were observe

Carotenoid Profiles in Pigment-Protein Complexes of Rhodospirillum rubrum

Young cells of Rhodospirillum rubrum contain a set of carotenoids from lycopene to spirilloxanthin. During growth, intermediates are almost completely converted to spirilloxan-thin. The ratio of the different carotenoid precursors vs. spirilloxanthin found in material of a certain age is the same in cells, chromatophores, light-harvesting complexes and reaction centers. Independent of the carotenoid composition and the age of the cells, the same detergent treatment can be used for isolation of pigment-protein complexes. Light-harvesting complexes of young cells containing mainly precursors of spirilloxanthin, as well as those of old cells in which spirilloxanthin dominates, both have their absorption maximum at 880 nm. It is thus assumed that all carotenoids of the spirilloxanthin series interact with bacteriochlorophyll a similarly to spirilloxanthin itself. From these results it is concluded that the micro-environment of these membrane-complexes is not influenced by the type of carotenoid present and that the assembly of the pigment-protein complexes in a growing membrane takes place before carotenoid biosynthesis has lead to the final produc

Influence of Temperature and pH on the Growth of the Thermophilic Cyanobacterium Mastigocladus laminosus in Continuous Culture

The thermophilic cyanobacterium Mastigocladus laminosus was grown in a steady state continuous culture. Regulation and data sampling of the turbidostat was done with a microcomputer. Growth performance was measured as a function of temperature and pH from 30 to 62°C and between pH 4 and 10. The temperature optimum was between 45 and 55°C. Under optimal conditions the filaments contained predominantly 8 cells with a high phycocyanin content but at the temperature extremes and at high pH, 2- and 4-cell filaments containing little phycocyanin were more abundan

Effects of natural and chemically synthesized furanones on quorum sensing in Chromobacterium violaceum

BACKGROUND: Cell to cell signaling systems in Gram-negative bacteria rely on small diffusible molecules such as the N-acylhomoserine lactones (AHL). These compounds are involved in the production of antibiotics, exoenzymes, virulence factors and biofilm formation. They belong to the class of furanone derivatives which are frequently found in nature as pheromones, flavor compounds or secondary metabolites. To obtain more information on the relation between molecular structure and quorum sensing, we tested a variety of natural and chemically synthesized furanones for their ability to interfere with the quorum sensing mechanism using a quantitative bioassay with Chromobacterium violaceum CV026 for antagonistic and agonistic action. We were looking at the following questions: 1. Do these compounds affect growth? 2) Do these compounds activate the quorum sensing system of C. violaceum CV026? 3) Do these compounds inhibit violacein formation induced by the addition of the natural inducer N-hexanoylhomoserine lactone (HHL)? 4) Do these compounds enhance violacein formation in presence of HHL? RESULTS: The naturally produced N-acylhomoserine lactones showed a strong non-linear concentration dependent influence on violacein production in C. violaceum with a maximum at 3.7*10(-8 )M with HHL. Apart from the N-acylhomoserine lactones only one furanone (emoxyfurane) was found to simulate N-acylhomoserine lactone activity and induce violacein formation. The most effective substances acting negatively both on growth and quorum sensing were analogs and intermediates in synthesis of the butenolides from Streptomyces antibioticus. CONCLUSION: As the regulation of many bacterial processes is governed by quorum sensing systems, the finding of natural and synthetic furanones acting as agonists or antagonists suggests an interesting tool to control and handle detrimental AHL induced effects. Some effects are due to general toxicity; others are explained by a competitive interaction for LuxR proteins. For further experiments it is important to be aware of the fact that quorum sensing active compounds have non-linear effects. Inducers can act as inhibitors and inhibitors might be able to activate or enhance the quorum sensing system depending on chemical structure and concentration levels

Light environment and synthesis of bacteriochlorophyll by populations of Chromatium okenii under natural environmental conditions

In the meromictic alpine Lake Cadagno a dense layer of phototrophic bacteria, mainly Chromatium okenii and Amoebobacter purpureus, develop annually at the chemocline at about 10 to 11 m depth. Radiometric spectral profiles of the incident sunlight demonstrate different attenuation coefficients in the mixolimnion and in the chemocline not only for the visible light effective at each depth (photosynthetically available radiation), but also for selected photosynthetically active wavelengths used by oxygenic and anoxygenic phototrophs. Phototrophic bacteria sampled from the upper part of the layer at the maximum of cell concentration were incubated in transparent bottles at the sampling depth and at a lower depth where the light intensity is only a few percent of the one at the sampling depth. Within 4 h the specific bacteriochlorophyll concentration (Bchl protein−1) increased up to 50% depending on the difference in light intensity between the sampling and the incubation depth. The specific bacteriochlorophyll concentration in the upper part of the layer remained constant (53.0 mg Bchl g−1 protein, S.D. = 4.8) in spite of large changes in cell concentrations in the lake water over the season. These observations illustrate the phenomenon of light-regulated pigment synthesis under natural condition

Microbial recovery of metals from solids

A variety of both lithotrophic and organotrophic microorganisms are known to mediate the mobilization of various elements from solids mostly by the formation of inorganic and organic acids. Under appropriate environmental conditions, metals are solubilized and extracted from metal-rich materials in subsurface ecosystems by the action of bacteria and fungi. In mine tailings or landfills microbial metal leaching represents a potential environmental hazard. However, these microbial activities can be successfully applied in the industry for the recovery of metals from solid materials such as ores or incineration residues. Microbial leaching processes are currently used for the winning of gold and copper from low-grade ores (‘bioleaching'). Solid industrial waste materials such as fly ash, sludges, or dust might also be microbially treated to recover metals for the re-use in metal-manufacturing industries. Bioleaching allows the cycling of metals by a process close to natural biogeochemical cycles reducing the demand for resources such as ores, energy, or landfill spac

Bacterial diversity and community composition in the chemocline of the meromictic alpine Lake Cadagno as revealed by 16S rDNA analysis

Using different techniques of molecular biology we investigated the bacterial diversity of the chemocline of the meromictic Lake Cadagno. Cloning of a total community 16S rDNA PCR product and subsequent screening with a combination of amplified ribosomal DNA restriction analysis and temporal temperature gradient gel electrophoresis (TTGE) analysis revealed that 30 of 47 randomly selected clones were unique. Partial sequencing and comparative analysis indicated a high bacterial diversity dominated by the γ-Proteobacteria (33.3%). Most of these rDNA clone sequences were not closely related to any 16S rDNA sequence in the database. In a second approach, the TTGE pattern from an environmental sample was compared with the migration of the cloned 16S rDNA fragments. Four clone types were identified on the environmental pattern by excising and sequencing comigrating bands, three of which were well represented in the library: two Chromatiaceae species and one sequence affiliated with the Desulfobulbus assemblage. Using the fluorescent in situ hybridization technique we essentially confirmed the results of the cloning experiments and the TTGE analysi