Cloning and characterization of groESL operon in Acetobacter aceti

The groESL operon of Acetobacter aceti was cloned and sequenced. We observed that GroES and GroEL of A. aced had high amino acid sequence homologies to GroES and GroEL of Escherichia coli and Bacillus subtilis. The upstream region of the groESL operon contained the heat-shock promoter, which was previously reported in alpha-purple proteobacteria, and the highly conserved inverted repeat sequence. Phylogenetic analysis revealed that the A. aced GroES and GroEL are very closely related to those of other alpha-purple proteobacteria. Transcription of this operon in A. aceti was induced by heat shock as well as by exposure to ethanol and acetic acid, which are present during fermentation of acetic acid. A. aced that overexpressed the groESL was more resistant than the control strain to stressors such as heat, ethanol, or acetic acid, indicating that GroES and GroEL are closely associated with the characteristic nature of Acetobacter and play an important role in acetic acid fermentation.