Synthesis, Release, and Recapture of Compatible Solute Proline by Osmotically Stressed Bacillus subtilis Cells

• DOI: 10.1128/aem.01040-12
• Publication Date: 2012-06-09T03:59:21Z
• Authors: Tamara Hoffmann; Carsten von Blohn; Agnieszka Stanek; Susanne Moses; Helena Barzantny; Erhard Bremer
• Keywords: Osmoregulation; Osmotic concentration; Osmotic shock; Ectoine; Growth medium

Bacillus subtilis synthesizes large amounts of the compatible solute proline as a cellular defense against high osmolarity to ensure physiologically appropriate level hydration cytoplasm and turgor. It also imports for this purpose via osmotically inducible OpuE transport system. Unexpectedly, an opuE mutant was at strong growth disadvantage in high-salinity minimal media lacking proline. Appreciable were detected culture supernatant strain, they rose concomitantly with increases external salinity. We found that intracellular pool severely salinity-stressed cells considerably lower than its opuE(+) parent strain. This loss into medium resulting decrease content provide rational explanation observed salt-sensitive phenotype OpuE. None known MscL- MscS-type mechanosensitive channels B. participated release under permanently imposed conditions. The data reported here show transporter not only possesses previously role scavenging exogenously provided osmoprotectant but functions highly important recapturing device is synthesized de novo subsequently released by salt-stressed cells. wider implications our findings retention solutes challenged microorganisms roles uptake systems are considered.