Changes in lipid and proteome composition accompany growth of Bacillus subterraneus MITOT1 under supercritical CO2 and may promote acclimation to associated stresses.

Abstract

Recent demonstration that multiple Bacillus strains grow in batch bioreactors containing supercritical (sc) CO2 (i.e. >73 atm, >31{degrees}C) is surprising given the recognized roles of scCO2 as a sterilant and solvent. Growth under scCO2 is of interest for biotechnological applications and for microbially-enhanced geologic carbon sequestration. We hypothesize that Bacillus spp. may alter cell wall and membrane composition in response to scCO2-associated stresses. In this study, protein expression and membrane lipids of B. subterraneus MITOT1 were profiled in cultures grown under headspaces of 1 and 100 atm of CO2 or N2. Growth under 100 atm CO2 revealed significantly decreased fatty acid branching and increased fatty acyl chain lengths relative to 1 atm cultures. Proteomes of MITOT1 grown under 1 and 100 atm pressures of CO2 and N2 were similar (Spearman R>0.65), and principal component analysis revealed variation by treatment with the first two principal components corresponding to headspace gas (CO2 or N2) and pressure (1 atm and 100 atm), respectively. Amino acid metabolic proteins were enriched under CO2, including the glycine cleavage system, previously shown to be upregulated in acid stress response. These results provide insights into the stationary phase physiology of strains grown under scCO2, suggesting modifications of cell membranes and amino acid metabolism may be involved in response to acidic, high CO2 conditions under scCO2.