Biomass production and energy source of thermophiles in a Japanese alkaline geothermal pool

Abstract

Microbial biomass production has been measured to investigate the contribution of planktonic bacteria to fluxations in dissolved organic matter in marine and freshwater environments, but little is known about biomass production of thermophiles inhabiting geothermal and hydrothermal regions. The biomass production of thermophiles inhabiting an 85 degrees C geothermal pool was measured by in situ cultivation using diffusion chambers. The thermophiles' growth rates ranged from 0.43 to 0.82 day(-1), similar to those of planktonic bacteria in marine and freshwater habitats. Biomass production was estimated based on cellular carbon content measured directly from the thermophiles inhabiting the geothermal pool, which ranged from 5.0 to 6.1 microg C l(-1) h(-1). This production was 2-75 times higher than that of planktonic bacteria in other habitats, because the cellular carbon content of the thermophiles was much higher. Quantitative PCR and phylogenetic analysis targeting 16S rRNA genes revealed that thermophilic H2-oxidizing bacteria closely related to Calderobacterium and Geothermobacterium were dominant in the geothermal pool. Chemical analysis showed the presence of H2 in gases bubbling from the bottom of the geothermal pool. These results strongly suggested that H2 plays an important role as a primary energy source of thermophiles in the geothermal pool.

In Situ Determination of Bacterial Growth in Mixing Zone of Hydrothermal Vent Field on the Hatoma Knoll, Southern Okinawa Trough

“…The growth rate of thermophiles inhabiting an 85 C geothermal pool has been measured by the similar in situ diffusion chamber tool, and recorded a range from 20 to 39 h doubling time under 0.2 mM sulfide in geothermal fluid (Kimura et al 2010). This range was a comparable result determined in 2 mM sulfide in the hydrothermal vent of Hatoma Knoll.…”

“…It has been applied in deep-sea expeditions for hydrothermal vents, and successfully isolated and/or accumulated novel chemolithotrophic bacteria Reysenbach et al 2000;Takai et al 2003). Of theses several types of in situ chambers, a diffusion chamber is a very useful apparatus for in situ physiological experiments of microbes (Bollmann et al 2007;McFeters and Stuart 1972;Vasconcelos and Swartz 1976), in situ determination of growth rate of phytoplankton (Furnas 1991) and thermophiles in alkaline geothermal pool (Kimura et al 2010).…”

Production and Consumption of Hydrogen in Hot Spring Microbial Mats Dominated by a Filamentous Anoxygenic Photosynthetic Bacterium

“…Nakabusa hot spring in Japan has been well-documented by geochemists and microbiologists in terms of its well-developed microbial mats (7–9, 11, 12, 19–22, 24, 30, 31, 40). The hot spring water is slightly alkaline (pH 8.3–8.9) and contains sulfide (~0.1 mM), sulfate (~0.1 mM) and low concentrations of organic compounds (0.4 mg L −1 total organic carbon) (24, 30, 31).…”

In Situ Biomass Production of a Hot Spring Sulfur-Turf Microbial Mat

“…From the microbial cell density and the carbon content, the cellular carbon content was roughly calculated to be 4.15±0.01 pg of C cell −1 (mean±standard deviation; n=9). The estimated biovolume and cellular carbon content were much higher than those of other natural microbes and bacterial strains (2,9,11,12). Ogawa and Maki (19) reported that sulfur-turf microbial mats produce gelatinous extracellular polysaccharides.…”

“…The growth rates ranged from 0.45 to 0.52 h −1 with an overall average of 0.48 h −1 ( Table 2). These growth rates were at least an order of magnitude higher than those of the phototrophic and heterotrophic bacterioplankton that inhabit marine environments (10,16,21), as well as the thermophiles that inhabited a geothermal pool of 85°C (9). From the growth rates determined in this study, the doubling time was calculated to range from 80 to 92 min.…”