An extracellular aminopeptidase encoded by the ywaD gene plays an important role in supplying nitrogen nutrition for the growth of Bacillus subtilis 168

Abstract

To investigate the physiological role of an extracellular aminopeptidase (BSAP168) encoded by the ywaD gene in Bacillus subtilis 168, we constructed the ywaD-deletion mutant (BS-AP-K). Compared with that of the wild-type strain, the maximum growth rate of BS-AP-K was reduced by 28% when grown in soybean protein medium at 37 °C, but not in Luria–Bertani medium. The impaired growth rate was more marked at higher temperature and could be compensated by supplementation of amino acid to the culture media. Further studies showed that in regards to the amino acid compositions and peptide distribution in the culture supernatants, there was an obvious difference between the culture supernatants of wild-type and BS-AP-K strains. In addition, another mutant strain (BS-AP-R) was constructed by replacing ywaD with ywaD-ΔPA to evaluate the effect of a protease-associated domain in BSAP168 on growth. All these findings indicated that BSAP168 played an important role in supplying the amino acids required for growth.