Regulation of acetate metabolism in Escherichia coli BL21 by protein Nε-lysine acetylation

Acetate production is one of the most striking differences between Escherichia coli K12 and BL21 strains. Transcription of acetate metabolism genes is regulated. Additionally, acetyl-CoA synthetase, which activates acetate to acetyl-CoA, is regulated by post-translational acetylation. The aim of this study was to understand the contribution of reversible protein lysine acetylation to the regulation of acetate metabolism in E. coli BL21. The phenotypic differences between both strains were especially important in the presence of acetate. The high expression of acetyl-CoA synthetase (acs) in glucose exponential phase in BL21 allows the simultaneous consumption of acetate and glucose. Lack of catabolite repression also affected its post-translational regulator, the protein acetyltransferase (patZ). The effect of the deletion of cobB (encoding a sirtuin-like protein deacetylase) and patZ genes depended on the genetic background. The deletion of cobB in both strains increased acetate production and decreased growth rate in acetate cultures. The deletion of patZ in BL21 suppressed acetate overflow in glucose medium and increased the growth rate in acetate cultures. Differences on acetate overflow between BL21 and K12 strains are caused by many overlapping factors. Two major contributing effects were identified: (1) the expression of acs during exponential growth is not repressed in the BL21 strain due to concomitant cAMP production and (2) the acetyl-CoA synthetase activity is more tightly regulated by protein acetylation in BL21 than in the K12. Altogether these differences contribute to the lower acetate overflow and the improved ability of E. coli BL21 to consume this metabolite in the presence of glucose.