Glutamine synthetase gene expression at elevated hydrostatic pressure in adeep-sea piezophilic Shewanella violacea

A glutamine synthetase gene (glnA) was isolated from a deep-sea piezophilic bacterium, Shewanella violacea strain DSS12. A 7.5-kb SacI fragment contai ning the complete glnA gene was cloned and sequenced. The glnA gene was fou nd to encode a protein consisting of 469 amino acid residues, showing 75.0% identity to the glutamine synthetase of Escherichia coli. Primer extension analyses revealed two transcription initiation sites in glnA and expressio n from each site was positively regulated by pressure. Putative promoters r ecognized by sigma (70) and sigma (54) were identified in the region upstre am of glnA. An electrophoretic mobility shift assay demonstrated that S. vi olacea sigma (54) specifically binds to the promoter region of glnA, sugges ting that sigma (54) may play an important role in pressure-regulated trans cription in this piezophilic bacterium. (C) 2000 Federation of European Mic robiological Societies. Published by Elsevier Science B.V. All rights reser ved.