Amy Banta

Thermodesulfobacterium hydrogeniphilum sp. nov., a thermophilic, chemolithoautotrophic, sulfate-reducing bacterium isolated from a deep-sea hydrothermal vent at Guaymas Basin, and emendation of the genus Thermodesulfobacterium

A thermophilic, non-spore-forming, marine, sulfate-reducing bacterium, strain SL6T, was isolated from deep-sea hydrothermal sulfides collected at Guaymas Basin. The gram-negative-staining cells occurred singly or in pairs as small, highly motile rods. The temperature range for growth was 50-80 degrees C with an optimum at 75 degrees C. The pH range for growth at 70 degrees C was 6.3-6.8, with an optimum at 6.5. The NaCl concentration range for growth was 5-55 g l(-1), with an optimum at 30 g l(-1). H2 and CO2 were the only substrates for growth and sulfate reduction. However, growth was stimulated by several organic compounds. Sulfur, thiosulfate, sulfite, cystine, nitrate and fumarate were not used as electron acceptors. Pyruvate, lactate and malate did not support fermentative growth. Desulfoviridin was not detected. The G+C content of the genomic DNA was 28 mol%. On the basis of 16S rRNA sequence analysis, strain SL6T is related to members of the genus Thermodesulfobacterium. However, the novel organism possesses phenotypic and phylogenetic traits that differ from those of its closest relatives. Therefore, it is proposed that this isolate, which constitutes the first marine representative of this genus, should be described as the type strain of a novel species, Thermodesulfobacterium hydrogeniphilum sp. nov. The type strain is SL6T (= DSM 14290T = JCM 11239T). Because of the phenotypic characteristics of the novel species, it is also proposed that the description of the genus Thermodesulfobacterium requires emendation.

Microbial essentials at hydrothermal vents.

Hot, anoxic fluids emerging from deep-sea hydrothermal vents mix suddenly with cold oxygenated sea water, providing ideal microbial niches for organisms that need limited amounts of oxygen. We have now identified and grown the first microaerophilic, thermophilic eubacterium from a deep-sea hydrothermal chimney. In view of the likely abundance of this type of microenvironment in hydrothermal structures, these newly discovered thermophilic microbes could constitute a large part of the microbial populations in seafloor hydrothermal systems.

Biogeochemistry: Microbial essentials at hydrothermal vents

Hot, anoxic fluids emerging from deep-sea hydrothermal vents mix suddenly with cold oxygenated sea water, providing ideal microbial niches for organisms that need limited amounts of oxygen. We have now identified and grown the first microaerophilic, thermophilic eubacterium from a deep-sea hydrothermal chimney. In view of the likely abundance of this type of microenvironment in hydrothermal structures, these newly discovered thermophilic microbes could constitute a large part of the microbial populations in seafloor hydrothermal systems.

Microbiological Comparison of Core and Groundwater Samples Collected from a Fractured Basalt Aquifer with that of Dialysis Chambers Incubated In Situ

Microorganisms associated with basalt core were compared to those suspended in groundwater pumped from the same well in the eastern Snake River Plain Aquifer (Idaho, USA). Two wells located at different distances from the source of a mixed-waste plume in the fractured basalt aquifer were examined. In the well more distal from the plume source, an array of dialysis chambers filled with either deionized water or crushed basalt was equilibrated to compare the microorganisms collected in this fashion with those from core and groundwater samples collected in a traditional manner from the same well. The samples were characterized to determine the total amount of biomass, presence of specific populations or physiological groups, and potential community functions. Microorganisms and their activities were nearly undetectable in core and groundwater collected from the well farthest from the plume source and substantially enriched in both core and groundwater from the well closest to the plume source. In both wells, differences (statistically significant for some measures) were found between bacteria associated with the cores and those suspended in the groundwater. Significantly higher populations were found in the basalt- and water-filled dialysis chambers incubated in the open well compared with core and groundwater samples, respectively. For a given parameter, the variation among dialysis chambers incubated at different depths was much less than the high variation observed among core samples. Analyses on selected basalt- and water-filled dialysis chamber samples suggested that these two communities were compositionally similar but exhibited different potential functions. Documented knowledge of cell physiological changes associated with attachment and potential differences between attached and unattached communities in aquifers indicate that careful consideration should be given to the type of sample media (i.e., core, groundwater, substrata incubated in a well) used to represent a subsurface environment.

Microbial essentials at hydrothermal vents : Biogeochemistry

Hot, anoxic fluids emerging from deep-sea hydrothermal vents mix suddenly with cold oxygenated sea water, providing ideal microbial niches for organisms that need limited amounts of oxygen. We have now identified and grown the first microaerophilic, thermophilic eubacterium from a deep-sea hydrothermal chimney. In view of the likely abundance of this type of microenvironment in hydrothermal structures, these newly discovered thermophilic microbes could constitute a large part of the microbial populations in seafloor hydrothermal systems.