Energetics ofAcidianus ambivalensgrowth in response to oxygen availability

摘要

All life requires energy to drive metabolic reactions such as growth and cell maintenance; therefore, fluctuations in energy availability can alter microbial activity. There is a gap in our knowledge concerning how energy availability affects the growth of extreme chemolithoautotrophs. Toward this end, we investigated the growth of thermoacidophileAcidianus ambivalensduring sulfur oxidation under aerobic to microaerophilic conditions. Calorimetry was used to measure enthalpy (Delta H-inc) of microbial activity, and chemical changes in growth media were measured to calculate Gibbs energy change (Delta G(inc)) during incubation. In all experiments, Gibbs energy was primarily dissipated through the release of heat, which suggests enthalpy-driven growth. In microaerophilic conditions, growth was significantly more efficient in terms of biomass yield (defined as C-mol biomass per mole sulfur consumed) and resulted in lower Delta G(inc)and Delta H-inc. Delta G(inc)in oxygen-limited (OL) and oxygen- and CO2-limited (OCL) microaerophilic growth conditions resulted in averages of -1.44 x 10(3) kJ/C-mol and -7.56 x 10(2) kJ/C-mol, respectively, and average Delta H(inc)values of -1.11 x 10(5) kJ/C-mol and -4.43 x 10(4) kJ/C-mol, respectively. High-oxygen experiments resulted in lower biomass yield values, an increase in Delta G(inc)to -1.71 x 10(4) kJ/C-mol, and more exothermic Delta H(inc)values of -4.71 x 10(5) kJ/C-mol. The observed inefficiency in high-oxygen conditions may suggest larger maintenance energy demands due to oxidative stresses and a preference for growth in microaerophilic environments.