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Sulfate-reducing bacteria and their activities in cyanobacterial mats of solar lake (Sinai, Egypt).

ABSTRACT: The sulfate-reducing bacteria within the surface layer of the hypersaline cyanobacterial mat of Solar Lake (Sinai, Egypt) were investigated with combined microbiological, molecular, and biogeochemical approaches. The diurnally oxic surface layer contained between 10(6) and 10(7) cultivable sulfate-reducing bacteria ml-1 and showed sulfate reduction rates between 1,000 and 2, 200 nmol ml-1 day-1, both in the same range as and sometimes higher than those in anaerobic deeper mat layers. In the oxic surface layer and in the mat layers below, filamentous sulfate-reducing Desulfonema bacteria were found in variable densities of 10(4) to 10(6) cells ml-1. A Desulfonema-related, diurnally migrating bacterium was detected with PCR and denaturing gradient gel electrophoresis within and below the oxic surface layer. Facultative aerobic respiration, filamentous morphology, motility, diurnal migration, and aggregate formation were the most conspicuous adaptations of Solar Lake sulfate-reducing bacteria to the mat matrix and to diurnal oxygen stress. A comparison of sulfate reduction rates within the mat and previously published photosynthesis rates showed that CO2 from sulfate reduction in the upper 5 mm accounted for 7 to 8% of the total photosynthetic CO2 demand of the mat.

SUBMITTER: Teske A

PROVIDER: S-EPMC106797 | biostudies-literature | 1998 Aug

REPOSITORIES: biostudies-literature

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Sulfate-reducing bacteria and their activities in cyanobacterial mats of solar lake (Sinai, Egypt).

Teske A A Ramsing N B NB Habicht K K Fukui M M Küver J J Jørgensen B B BB Cohen Y Y

Applied and environmental microbiology 19980801 8

The sulfate-reducing bacteria within the surface layer of the hypersaline cyanobacterial mat of Solar Lake (Sinai, Egypt) were investigated with combined microbiological, molecular, and biogeochemical approaches. The diurnally oxic surface layer contained between 10(6) and 10(7) cultivable sulfate-reducing bacteria ml-1 and showed sulfate reduction rates between 1,000 and 2, 200 nmol ml-1 day-1, both in the same range as and sometimes higher than those in anaerobic deeper mat layers. In the oxic ...[more]

PMID: 9687455

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Project description:Calcifying microbial mats in hypersaline environments are important model systems for the study of the earliest ecosystems on Earth that started to appear more than three billion years ago and have been preserved in the fossil record as laminated lithified structures known as stromatolites. It is believed that sulfate-reducing bacteria play a pivotal role in the lithification process by increasing the saturation index of calcium minerals within the mat. Strain L21-Syr-ABT was isolated from anoxic samples of a several centimeters-thick microbialite-forming cyanobacterial mat of a hypersaline lake on the Kiritimati Atoll (Kiribati, Central Pacific). The novel isolate was assigned to the family Desulfovibrionaceae within the Deltaproteobacteria. Available 16S rRNA-based population surveys obtained from discrete layers of the mat indicate that the occurrence of a species-level clade represented by strain L21-Syr-ABT is restricted to a specific layer of the suboxic zone, which is characterized by the presence of aragonitic spherulites. To elucidate a possible function of this sulfate-reducing bacterium in the mineral formation within the mat a comprehensive phenotypic characterization was combined with the results of a comparative genome analysis. Among the determined traits of strain L21-Syr-ABT, several features were identified that could play a role in the precipitation of calcium carbonate: (i) the potential deacetylation of polysaccharides and consumption of substrates such as lactate and sulfate could mobilize free calcium; (ii) under conditions that favor the utilization of formate and hydrogen, the alkalinity engine within the mat is stimulated, thereby increasing the availability of carbonate; (iii) the production of extracellular polysaccharides could provide nucleation sites for calcium mineralization. In addition, our data suggest the proposal of the novel species and genus Desulfohalovibrio reitneri represented by the type strain L21-Syr-ABT (=DSM 26903T = JCM 18662T).

Dataset Information

Sulfate-reducing bacteria and their activities in cyanobacterial mats of solar lake (Sinai, Egypt).

Publications

Sulfate-reducing bacteria and their activities in cyanobacterial mats of solar lake (Sinai, Egypt).

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