Changes in protein synthesis during the adaptation of Bacillus subtilis to anaerobic growth conditions.

Abstract

After a shift of Bacillus subtilis from aerobic to anaerobic growth conditions, nitrate ammonification and various fermentative processes replace oxygen-dependent respiration. Cell-free extracts prepared from wild-type B. subtilis and from mutants of the regulatory loci fnr and resDE grown under aerobic and various anaerobic conditions were compared by two-dimensional gel electrophoresis. Proteins involved in the adaptation process were identified by their N-terminal sequence. Induction of cytoplasmic lactate dehydrogenase (LctE) synthesis under anaerobic fermentative conditions was dependent on fnr and resDE. Anaerobic nitrate repression of LctE formation required fnr-mediated expression of narGHJI, encoding respiratory nitrate reductase. Anaerobic induction of the flavohaemoglobin Hmp required resDE and nitrite. The general anaerobic induction of ywfl, encoding a protein of unknown function, was modulated by resDE and fnr. The ywfl gene shares its upstream region with the pta gene, encoding the fermentative enzyme acetyl-CoA:orthophosphate acetyltransferase. Anaerobic repression of the synthesis of a potential membrane-associated NADH dehydrogenase (YjlD, Ndh), and anaerobic induction of fructose-1,6-bisphosphate aldolase (FbaA) and dehydrolipoamide dehydrogenase (PhdD, Lpd) formation, did not require fnr or resDE participation. Synthesis of glycerol kinase (GlpK) was decreased under anaerobic conditions. Finally, the effect of anaerobic stress induced by the immediate shift from aerobic to strictly anaerobic conditions was analysed. The induction of various systems for the utilization of alternative carbon sources such as inositol (IoIA, IoIG, IoIH, IoII), melibiose (MeIA) and 6-phospho-alpha-glucosides (GIvA) indicated a catabolite-response-like stress reaction.