Expression dynamics of the poly-γ-glutamic acid biosynthesis genes of Bacillus subtilis in response to glucose and glutamic acid-A pilot study

Abstract

Poly-γ-glutamic acid (PGA) is biosynthesized by various Bacillus species through PGA synthetase, encoded by PGA operon comprising of ywsC and ywtABC genes. Due to the minimal available knowledge, understanding the expression pattern of PGA operon genes is pivotal. In this study, the effect of glucose and glutamic acid on global gene expression profile of Bacillus subtilis Natto3 was investigated using high throughput microarray, with an emphasis on PGA operon and genes influencing PGA production. Two treatment groups (set1-in presence of glutamic acid and set2-in presence of glutamic acid+glucose) were analyzed against control, (in presence of glucose). In Microarray, both the groups, showed trend of up-regulation for ywsC and ywtA genes (log2 fold change of 0.55, p=0.0194, 0.92, p=0.0069 in set1 and 0.78, p=0.0023, 0.59, p=0.0172 in set2, respectively) and down-regulation of ywtB and ywtC genes (log2 fold change of -1.83, p=0.0001, -1.42, p=0.0017 in set1 and -1.52, p=0.0012, -0.55, p=0.1112 in set2, respectively), supporting indispensability of ywsC and ywtA genes in PGA production. Interestingly, ywtB and ywtC genes, belonging to the same operon were down-regulated in both the conditions (set1 and set2). To the best of our knowledge, this expression pattern of PGA operon genes is a unique observation.