Comprehensive Detection of Phototrophic Sulfur Bacteria Using PCR Primers That Target Reverse Dissimilatory Sulfite Reductase Gene

Green sulfur bacteria (GSB) oxidize sulfide and thiosulfate to sulfate, with extracellular globules of elemental sulfur as an intermediate. Here we investigated which genes are involved in the formation and consumption of these sulfur globules in the green sulfur bacterium Chlorobaculum tepidum. We show that sulfur globule oxidation is strictly dependent on the dissimilatory sulfite reductase (DSR) system. Deletion of dsrM/CT2244 or dsrT/CT2245, or the two dsrCABL clusters (CT0851–CT0854, CT2247–2250), abolished sulfur globule oxidation and prevented formation of sulfate from sulfide, whereas deletion of dsrU/CT2246 had no effect. The DSR system also seems to be involved in the formation of thiosulfate, because thiosulfate was released from wild-type cells during sulfide oxidation, but not from the dsr mutants. The dsr mutants incapable of complete substrate oxidation oxidized sulfide and thiosulfate about twice as fast as the wild-type, while having only slightly lower growth rates (70–80 % of wild-type). The increased oxidation rates seem to compensate for the incomplete substrate oxidation to satisfy the requirement for reducing equivalents during growth. A mutant in which two sulfide : quinone oxidoreductases (sqrD/CT0117 and sqrF/CT1087) were deleted exhibited a decreased sulfide oxidation rate (∼50 % of wild-type), yet formation and consumption of sulfur globules were not affected. The observation that mutants lacking the DSR system maintain efficient growth suggests that the DSR system is dispensable in environments with sufficiently high sulfide concentrations. Thus, the DSR system in GSB may have been acquired by horizontal gene transfer as a response to a need for enhanced substrate utilization in sulfide-limiting habitats.

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Characterization of the marine propionate-degrading, sulfate-reducing bacterium Desulfofaba fastidiosa sp. nov. and reclassification of Desulfomusa hansenii as Desulfofaba hansenii comb. nov.

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.02820-0 ◽

2004 ◽

Vol 54 (2) ◽

pp. 393-399 ◽

Cited By ~ 25

Author(s):

Lone Abildgaard ◽

Niels Birger Ramsing ◽

Kai Finster

Keyword(s):

Small Subunit ◽

Phenotypic Traits ◽

Rrna Gene ◽

Sulfate Reducing ◽

Dissimilatory Sulfite Reductase ◽

Small Subunit Rdna ◽

Reductase Gene ◽

Morphological And Physiological Traits ◽

Dissimilatory Sulfite Reductase Gene

A rod-shaped, slightly curved sulfate reducer, designated strain P2T, was isolated from the sulfate–methane transition zone of a marine sediment. Cells were motile by means of a single polar flagellum. The strain reduced sulfate, thiosulfate and sulfite to sulfide and used propionate, lactate and 1-propanol as electron donors. Strain P2T also grew by fermentation of lactate. Propionate was oxidized incompletely to acetate and CO2. The DNA G+C content was 48·8mol%. Sequence analysis of the small-subunit rDNA and the dissimilatory sulfite reductase gene revealed that strain P2T was related to the genera Desulfonema, Desulfococcus, Desulfosarcina, ‘Desulfobotulus’, Desulfofaba, Desulfomusa and Desulfofrigus. These genera include incomplete as well as complete oxidizers of substrates. Strain P2T shared important morphological and physiological traits with Desulfofaba gelida and Desulfomusa hansenii, including the ability to oxidize propionate incompletely to acetate. The 16S rRNA gene similarities of P2T to Desulfofaba gelida and Desulfomusa hansenii were respectively 92·9 and 91·5%. Combining phenotypic and genotypic traits, we propose strain P2T to be a member of the genus Desulfofaba. The name Desulfofaba fastidiosa sp. nov. (type strain P2T=DSM 15249T=ATCC BAA-815T) is proposed, reflecting the limited number of substrates consumed by the strain. In addition, the reclassification of Desulfomusa hansenii as a member of the genus Desulfofaba, Desulfofaba hansenii comb. nov., is proposed. A common line of descent and a number of shared phenotypic traits support this reclassification.

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Congruent Phylogenies of Most Common Small-Subunit rRNA and Dissimilatory Sulfite Reductase Gene Sequences Retrieved from Estuarine Sediments

Applied and Environmental Microbiology ◽

10.1128/aem.67.7.3314-3318.2001 ◽

2001 ◽

Vol 67 (7) ◽

pp. 3314-3318 ◽

Cited By ~ 53

Author(s):

Catherine Joulian ◽

Niels B. Ramsing ◽

Kjeld Ingvorsen

Keyword(s):

Target Genes ◽

Small Subunit ◽

Estuarine Sediments ◽

Sulfite Reductase ◽

Small Subunit Rrna ◽

Sulfate Reducing ◽

Dissimilatory Sulfite Reductase ◽

Phylogenetic Affiliation ◽

Reductase Gene ◽

Reducing Bacteria

ABSTRACT The diversity of sulfate-reducing bacteria (SRB) in brackish sediment was investigated using small-subunit rRNA and dissimilatory sulfite reductase (DSR) gene clone libraries and cultivation. The phylogenetic affiliation of the most commonly retrieved clones for both genes was strikingly similar and producedDesulfosarcina variabilis-like sequences from the inoculum but Desulfomicrobium baculatum-like sequences from a high dilution in natural media. Related organisms were subsequently cultivated from the site. PCR bias appear to be limited (or very similar) for the two primersets and target genes. However, the DSR primers showed a much higher phylogenetic specificity. DSR gene analysis is thus a promising and specific approach for investigating SRB diversity in complex habitats.

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Anoxygenic photo- and chemosynthesis of phototrophic sulfur bacteria from an alpine meromictic lake

FEMS Microbiology Ecology ◽

10.1093/femsec/fiab010 ◽

2021 ◽

Author(s):

Francesco Di Nezio ◽

Clarisse Beney ◽

Samuele Roman ◽

Francesco Danza ◽

Antoine Buetti-Dinh ◽

...

Keyword(s):

Carbon Fixation ◽

Meromictic Lake ◽

Purple Sulfur Bacterium ◽

Phototrophic Sulfur Bacteria ◽

Anaerobic Microorganisms ◽

Sulfur Bacteria ◽

Pure Cultures ◽

Chlorobium Phaeobacteroides ◽

Anoxic Environment ◽

Dark Carbon Fixation

Abstract Meromictic lakes are interesting ecosystems to study anaerobic microorganisms due their permanent stratification allowing the formation of a stable anoxic environment. The crenogenic meromictic Lake Cadagno harbors an important community of anoxygenic phototrophic sulfur bacteria responsible for almost half of its total productivity. Besides their ability to fix CO2 through photosynthesis, these microorganisms also showed high rates of dark carbon fixation via chemosyntesis. Here, we grew in pure cultures three populations of anoxygenic phototrophic sulfur bacteria previously isolated from the lake, accounting for 72.8% of the total microbial community, and exibiting different phenotypes: 1) the motile, large-celled purple sulfur bacterium (PSB) Chromatium okenii, 2) the small-celled PSB Thiodictyon syntrophicum, and 3) the green sulfur bacterium (GSB) Chlorobium phaeobacteroides. We measured their ability to fix CO2 through photo- and chemo-synthesis, both in situ in the lake and in laboratory under different incubation conditions. We also evaluated the efficiency and velocity of H2S photo-oxidation, an important reaction in the anoxygenic photosynthesis process. Our results confirm that phototrophic sulfur bacteria strongly fix CO2 in the presence of light and that oxygen increases chemosynthesis at night, in laboratory conditions. Moreover, substancial differences were displayed between the three selected populations in terms of activity and abundance.

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