The ilvGMEDA operon is regulated by transcription attenuation in Vibrio alginolyticus ZJ-T

Abstract

Bacteria synthesize amino acids according to their availability in the environment or, in the case of pathogens, within the host. We explored the regulation of the biosynthesis of branched-chain amino acids (BCAAs) (L-leucine, L-valine, and L-isoleucine) in Vibrio alginolyticus, a marine fish and shellfish pathogen and an emerging opportunistic human pathogen. In this species, the ilvGMEDA operon encodes the main pathway for biosynthesis of BCAAs. Its upstream regulatory region shows no sequence similarity to the corresponding region in Escherichia coli or other Enterobacteriaceae, and yet we show that this operon is regulated by transcription attenuation. The translation of a BCAA-rich peptide encoded upstream of the structural genes provides an adaptive response similar to the E. coli canonical model. This study of a nonmodel Gram-negative organism highlights the mechanistic conservation of transcription attenuation despite the absence of primary sequence conservation.