Carbon isotopic fractionations associated wit thermophilic bacteria Thermotoga maritima and Persephonella marina

摘要

Stable carbon isotopes can provide insight into carbon cycling pathways in natural environments. We examined carbon isotope fractionations associated with a hyperthermophilic fermentative bacterium, Thermotoga maritima, and a thermophilic chemo-lithoautotrophic bacterium Persephonella marina. In T. maritina, phospholipid fatty acids (PLFA) are slightly enriched in ~(13)C relative to biomass (ε = 0.1-0.8‰). However, PLFA and biomass are depleted in ~(13)C relative to the substrate glucose by ～8‰. IN P. marina, PLFA are 1.8-14.5‰ enriched in ~(13)C relative to biomass, which suggests that the reversed tricar-boxylic acid (TCA) cycle or the 3-hydroxypropionate pathway may be used for CO_2 fixation. This is supported by small fractionation between biomass and CO_2 (ε = -3.8‰ to -5.0‰), which is similar to fractionations reported for other organisms using similar CO_2 fixation pathways. Identification of the exact pathway will require biochemical assay for specific enzymes associated with the reversed TCA cycle or the 3-hydroxypropionate pathway.