Key internal factors leading to the variability in CO_2 fixation efficiency of different sulfur-oxidizing bacteria during autotrophic cultivation

摘要

Variability in the apparent CO_2 fixation yield of four aerobic sulfur-oxidizing bacteria (Halothiobacillus neapoli-tanus DSM 15147, Thiobacillus thioparus DSM 505, Thiomonas intermedia DSM 18155, and Starkeya novella DSM 506) in autotrophic culturing was studied, and mutual effects of key intrinsic factors on CO_2 fixation were explored. DSM 15147 and DSM 505 exhibited much higher CO_2 fixation yields than DSM 18155 and DSM 506. The differences in CO_2 fixation yield were determined not only by ebb gene transcription, but also by cell synthesis rate, which was determined by rRNA gene copy number; the rRNA gene copy number had a more significant effect than cbb gene transcription on the apparent CO_2 fixation yield. Moreover, accumulation of EDOC was observed in all four strains during chemoautotrophic cultivation, and the proportion of EDOC accounting for total fixed organic carbon (TOC; EDOC/TOC ratio) was much higher in DSM 18155 and DSM 506 than in DSM 15147 and DSM 505. The accumulation of EDOC led to a significant decrease in the ebb gene transcription efficiency during cultivation, and a further feedback inhibitory effect on CO_2 fixation.