Effect of overexpression of proline dehydrogenase on high saline adaptation through proline utilization in Escherichia coli

Abstract

The effect of the amount of proline dehydrogenase PutA expression on the mechanism of adaptation of Escherichia coli cells under high salinity was analyzed. The PutA gene derived from E. coli expression plasmid was introduced into E. coli cell, and PutA high expression strain BL21-PutA was developed. Transcription of the PutA was induced by the addition of gene expression inducer IPTG, and high transcription was observed under 1 M NaCl condition. Growth of E. coli BL21-PutA in a Davis minimal medium was inhibited under 1 M NaCl condition, but it was remarkably recovered by the addition of L-proline. On the other hand, the recovery of growth in the presence of L-proline was inhibited when IPTG was added. Under 1 M NaCl condition, L-proline was quickly accumulated in cells, regardless of the strains. On the other hand, intracellular concentration of L-proline in BL21-PutA cells cultured with IPTG was lower than BL21 cells. These data suggested that the amount of the expression of PutA affected the adaptation of high salinity with L-proline in E. coli cells. Key words: Escherichia coli, high salinity adaptation, proline dehydrogenase PutA, overexpression