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Correlative light/electron microscopy for the investigation of microbial mats from Black Sea Cold Seeps
No full textIn several fields of cell biology, correlative microscopy is applied to compare the structure of objects at high resolution under the electron microscope with low resolution light microscopy images of the same sample. It is, however, difficult to prepare samples and marker systems that are applicable for both microscopic techniques for the same specimen at the same time. In our studies, we used microbial mats from Cold Seep communities for a simple and rapid correlative microscopy method. The mats consist of bacterial and archaeal microorganisms, coupling reverse methanogenesis to the reduction of sulfate. The reverse methanogenic pathway also generates carbonates that precipitate inside the mat and may be the main reason for the formation of a microbial reef. The mat shows highly differentiated aggregates of various organisms, tightly interconnected by extracellular polysaccharides. In order to investigate the role of EPS as adhesive mucilage for the biofilm and as a precipitation matrix for carbonate minerals, samples were embedded in a hydrophilic resin (Lowicryl K4 M). Sections were suitable for light as well as electron microscopy in combination with lectins, either labeled with a fluorescent marker or with colloidal gold. This allows lectin mapping at low resolution for light microscopy in direct comparison with a highly resolved electron microscopic image
Archaea in Symbioses
Full text linkDuring the last few years, the analysis of microbial diversity in various habitats greatly increased our knowledge on the kingdom
Archaea. At the same time, we became aware of the multiple ways in which Archaea may interact with each other and with
organisms of other kingdoms. The large group of euryarchaeal methanogens and their methane oxidizing relatives, in particular,
take part in essential steps of the global methane cycle. Both of these processes, which are in reverse to each other, are partially
conducted in a symbiotic interaction with different partners, either ciliates and xylophagous animals or sulfate reducing bacteria.
Other symbiotic interactions are mostly of unknown ecological significance but depend on highly specific mechanisms. This paper
will give an overview on interactions between Archaea and other organisms and will point out the ecological relevance of these
symbiotic processes, as long as these have been already recognized
A novel in situ detection technique of metabolic enzymes in Black Sea methane seep microbial mats
No full textA novel in situ detection technique of metabolic enzymes in Black Sea methane seep microbial mats
No full textLocalization of methyl-coenzyme M reductase as metabolic marker for diverse methanogenic archaea
Full text linkMethyl-Coenzyme M reductase (MCR) as key enzyme for methanogenesis as well as for anaerobic oxidation of methane represents an important metabolic marker for both processes in microbial biofilms. Here, the potential of MCR-specific polyclonal antibodies as metabolic marker in various methanogenic Archaea is shown. For standard growth conditions in laboratory culture, the cytoplasmic localization of the enzyme in Methanothermobacter marburgensis, Methanothermobacter wolfei, Methanococcus maripaludis, Methanosarcina mazei, and in anaerobically methane-oxidizing biofilms is demonstrated. Under growth limiting conditions on nickel-depleted media, at low linear growth of cultures, a fraction of 50-70% of the enzyme was localized close to the cytoplasmic membrane, which implies "facultative" membrane association of the enzyme. This feature may be also useful for assessment of growth-limiting conditions in microbial biofilms
The fingerprint of chemosymbiosis: origin and preservation of isotopic biosignatures in the nonseep bivalve Loripes lacteus compared with Venerupis aurea
No full textEndosymbionts in marine bivalves leave characteristic biosignatures in their host organisms. Two nonseep bivalve species collected in Mediterranean lagoons, thiotrophic symbiotic Loripes lacteus and filter-feeding nonsymbiotic Venerupis aurea, were studied in detail with respect to generation and presence of such signatures in living animals, and the preservation of these signals in subfossil (late Pleistocene) sedimentary shells. Three key enzymes from sulfur oxidation (APS-reductase), CO2 fixation (RubisCO) and assimilation of nitrogen [glutamine synthetase (GS)] were detected by immunofluorescence in the bacterial symbionts of Loripes. In Loripes, major activity was derived from GS of the symbionts whereas in Venerupis the host GS is active. In search of geologically stable biosignatures for thiotrophic chemosymbiosis that might be suitable to detect such associations in ancient bivalves, we analyzed the isotopic composition of shell lipids (d 13C ) and the bulk organic matrix of the shell (d 13C , d 15N , d 34S ). In the thiotrophic Loripes, d 13C values were depleted compared with the filter-feeding Venerupis by as much as 8.5 parts per thousand for individual fatty acids, and 4.4 parts per thousand for bulk organic carbon. Likewise, bulk d 15N and d 34S values were more depleted in recent thiotrophic Loripes. Whereas d 34S values were found to be unstable over time, the combined d 15N and d 13C values in organic shell extracts revealed a specific signature for chemosymbiosis in recent and subfossil specimens
Dynamic Localization of a Transcription Factor in Bacillus subtilis: the LicT Antiterminator Relocalizes in Response to Inducer Availability
No full textBacillus subtilis transports beta-glucosides such as salicin by a dedicated phosphotransferase system (PTS). The expression of the beta-glucoside permease BglP is induced in the presence of the substrate salicin, and this induction requires the binding of the antiterminator protein LicT to a specific RNA target in the 5' region of the bglP mRNA to prevent the formation of a transcription terminator. LicT is composed of an N-terminal RNA-binding domain and two consecutive PTS regulation domains, PRD1 and PRD2. In the absence of salicin, LicT is phosphorylated on PRD1 by BglP and thereby inactivated. In the presence of the inducer, the phosphate group from PRD1 is transferred back to BglP and consequently to the incoming substrate, resulting in the activation of LicT. In this study, we have investigated the intracellular localization of LicT. While the protein was evenly distributed in the cell in the absence of the inducer, we observed a subpolar localization of LicT if salicin was present in the medium. Upon addition or removal of the inducer, LicT rapidly relocalized in the cells. This dynamic relocalization did not depend on the binding of LicT to its RNA target sites, since the localization pattern was not affected by deletion of all LicT binding sites. In contrast, experiments with mutants affected in the PTS components as well as mutations of the LicT phosphorylation sites revealed that phosphorylation of LicT by the PTS components plays a major role in the control of the subcellular localization of this RNA-binding transcription factor
Deposition of biogenic iron minerals in a methane oxidizing microbial mat.
Full text linkThe syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates
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