SerC Is involved in vitamin B 6 biosynthesis in Escherichia coli but not in Bacillus subtilis

Abstract

The possible involvement of serC in vitamin B 6 (B 6) biosynthesis in Bacillus subtilis was investigated and compared with that in Escherichia coli. The genes of E. coli and B. subtilis were disrupted with pBEN66 and pMutin1-derived integration vectors, respectively. Nutrient requirement analyses showed that the serC-disrupted E. coli mutant required pyridoxine (PN) and l-serine, and lacked the ability to synthesize B 6. Glycolaldehyde (GA), a confirmed precursor of B 6, could replace PN and support the growth of the disruptant. However, the serC-disrupted E. coli mutant grown in a minimal medium supplemented with l-serine and GA synthesized B 6 at a level less than 20% of that synthesized by the wild type. In contrast to E. coli, the serC-disrupted B. subtilis mutant required L-serine or glycine for growth, but did not require PN. The serC disruptant retained its ability for B 6 biosynthesis and produced almost the same amount of PN as the wild type. GA had no effect on the growth and level of B 6 biosynthesis of both the wild type and the serC disruptant. These results lead to the conclusion that serC is directly involved in B 6 biosynthesis in E. coli, but not in B. subtilis.