Changes in lipid and proteome composition accompany growth ofBacillus subterraneusMITOT1 under supercritical CO2and may promote acclimation to associated stresses

Recent demonstration that multiple Bacillus strains grow in batch bioreactors containing supercritical (sc) CO 2 (i.e. >73 atm, >31°C) is surprising given the recognized roles of scCO 2 as a sterilant and solvent. Growth under scCO 2 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 scCO 2 -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 CO 2 or N 2 . Growth under 100 atm CO 2 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 CO 2 and N 2 were similar (Spearman R>0.65), and principal component analysis revealed variation by treatment with the first two principal components corresponding to headspace gas (CO 2 or N 2 ) and pressure (1 atm and 100 atm), respectively. Amino acid metabolic proteins were enriched under CO 2 , 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 scCO 2 , suggesting modifications of cell membranes and amino acid metabolism may be involved in response to acidic, high CO 2 conditions under scCO 2 .