Regulation of the Escherichia coli water channel gene aqpZ

Giuseppe Calamita, Bettina Kempf, Mélanie Bonhivers, William R. Bishai, Erhard Bremer, Peter Agre

Research output: Contribution to journalArticlepeer-review

Abstract

Osmotic movement of water across bacterial cell membranes is postulated to be a homeostatic mechanism for maintaining cell turgor. The molecular water transporter remained elusive until discovery of the Escherichia coli water channel, AqpZ, however the regulation of the aqpZ gene expression and physiological function of the AqpZ protein are unknown. Northern analysis revealed a transcript of 0.7 kb, confirming the monocistronic nature of aqpZ. Regulatory studies performed with an aqpZ::lacZ low copy plasmid demonstrate enhanced expression during mid-logarithmic growth, and expression of the gene is dependent upon the extracellular osmolality, which increased in hypoosmotic environments but strongly reduced in hyperosmolar NaCl or KCl. While disruption of the chromosomal aqpZ is not lethal for E. coli, the colonies of the aqpZ knockout mutant are smaller than those of the parental wild-type strain. When cocultured with parental wild-type E. coli, the aqpZ knockout mutant exhibits markedly reduced colony formation when grown at 39°C. Similarly, the aqpZ knockout mutant also exhibits greatly reduced colony formation when grown at low osmolarity, but this phenotype is reversed by overexpression of AqpZ protein. These results implicate AqpZ as a participant in the adaptive response of E. coli to hypoosmotic environments and indicate a requirement for AqpZ by rapidly growing cells.

Original languageEnglish (US)
Pages (from-to)3627-3631
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number7
DOIs
StatePublished - Mar 31 1998

Keywords

  • Aquaporins
  • Bacteria
  • Osmoregulation
  • Water transport

ASJC Scopus subject areas

  • General

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