Effects on Bacillus subtilis of conditional expression of the accBC operon encoding subunits of acetyl coenzyme A carboxylase, the first enzyme of fatty acid synthesis.

Abstract

A Bacillus subtilis strain was constructed in which the operon accBC, encoding the biotin carboxyl carrier protein (BCCP) and biotin carboxylase (BC) subunits of acetyl-CoA carboxylase (ACC), was placed under the control of the IPTG-inducible promoter spac. A reduction in the levels of BCCP resulted in a decrease of de novo fatty acid synthesis and in the total content of membrane fatty acids. This strain was dependent upon the presence of IPTG for a normal growth phenotype. Growth was specifically restored by supplying exogenous long branched-chain fatty acids in the medium, indicating that the inducer-dependent phenotype was specifically related to a conditional block in fatty acid biosynthesis. The strain showed a strong decrease in sporulation frequency when it was induced to sporulate in an IPTG-free medium. Germination and outgrowth were both delayed in spores of the mutant obtained in the absence of IPTG.