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

Bacillus subtilis can attain cellular protection against the detrimental effects of high osmolarity through osmotically induced de novo synthesis and uptake of the compatible solute L-proline. We have now found that B. subtilis can also exploit exogenously provided proline-containing peptides of various lengths and compositions as osmoprotectants. Osmoprotection by these types of peptides is generally dependent on their import via the peptide transport systems (

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SynopsisDuring the past few decades, there has been an increased interest in the essential role of commensal skin bacteria in human body odour formation. It is now generally accepted that skin bacteria cause body odour by biotransformation of sweat components secreted in the human axillae. Especially, aerobic corynebacteria have been shown to contribute strongly to axillary malodour, whereas other human skin residents seem to have little influence. Analysis of odoriferous sweat components has shown that the major odour-causing substances in human sweat include steroid derivatives, short volatile branched-chain fatty acids and sulphanylalkanols. In this minireview, we describe the molecular basis of the four most extensively studied routes of human body odour formation, while focusing on the underlying enzymatic processes. Considering the previously reported role of b-oxidation in odour formation, we analysed the genetic repertoire of eight Corynebacterium species concerning fatty acid metabolism. We particularly focused on the metabolic abilities of the lipophilic axillary isolate Corynebacterium jeikeium K411. Ré suméPendant les décennies passées, il ya eu un intérêt croissant pour le rôle essentiel des bactéries commensales de la peau dans la formation des odeurs du corps humain. Il est maintenant généralement admis que les bactéries de la peau sont à l'origine de ces odeurs corporelles par biotransformation de composants de la sueur axillaire. On a, en particulier, montré que les corynebacteria aérobiques contribuent fortement à l'odeur axillaire, tandis que d'autres rési-dents de la peau semblent avoir une influence moindre. L'analyse de composants odoriférants de la sueur a montré que les substances majoritairement responsables de l'odeur incluent des dérivées de stéroïdes, des acides gras volatils à courtes chaines et des sulphanylalcanols. Dans cette mini revue, nous décrivons les bases molécu-laires des quatre voies les plus largement étudiées dans la formation des odeurs corporelles, en nous concentrant sur les processus enzymatiques sous-jacents. En considérant le rôle précédemment décrit de la b oxydation dans la formation d'odeur, nous avons analysé le répertoire génétique de huit espèces de Corynebacterium concernant le métabolisme des acide gras. Nous nous sommes particulièrement concentrés sur les capacités métaboliques de Corynebacterium jeikeium K411 isolé de la composante lipophile axillaire.

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