Transient Accumulation of Glycine Betaine and Dynamics of Endogenous Osmolytes in Salt-Stressed Cultures of Sinorhizobium meliloti.

The fate of exogenously supplied glycine betaine and the dynamics of endogenous osmolytes were investigated throughout the growth cycle of salt-stressed cultures of strains of Sinorhizobium meliloti which differ in their ability to use glycine betaine as a growth substrate, but not as an osmoprotectant. We present (sup13)C nuclear magnetic resonance spectral and radiotracer evidence which demonstrates that glycine betaine is only transiently accumulated as a cytoplasmic osmolyte in young cultures of wild-type strains 102F34 and RCR2011. Specifically, these strains accumulate glycine betaine as a preferred osmolyte which virtually prevents the accumulation of endogenous osmolytes during the lag and early exponential phases of growth.

Survival and recovery of viable but noncultivable forms of Campylobacter in aqueous microcosm.

Previous studies suggesting that the persistence of thermotolerant Campylobacter in water, especially as a viable but non-cultivable form (VNC), was involved in human campylobacteriosis, the capacities of survival and resuscitation of a significant collection of 85 strains in aqueous microcosms were investigated. Two-thirds of these strains (68%) were not detectable on agar medium after a stay of 14-21 days, whereas 21% reached this state before 14 days and 11% were non-cultivable after a stay of 21 days. Some strains remained cultivable after 35 days in a shaken aqueous microcosm and beyond 60 days without shaking.

Osmoadaptation in rhizobia: ectoine-induced salt tolerance.

After having shown that ectoine (a tetrahydropyrimidine) displays osmoprotective properties towards Escherichia coli (M. Jebbar, R. Talibart, K.

Pipecolic acid is an osmoprotectant for Escherichia coli taken up by the general osmoporters ProU and ProP.

Exogenously supplied L-pipecolic acid was accumulated by Escherichia coli cells and protected them while growing at inhibitory osmolarity. Using specific uptake mutants and competitive assays, we established that the imino acid enters the cells through the ProP and ProU systems with Km values of 225 and 53 microM, respectively. Surprisingly, in spite of the requirement for the wild-type proX gene for osmoprotective ability, no binding activity of labelled pipecolate with the periplasmic protein encoded by proX could be detected.

Osmoprotection of Escherichia coli by ectoine: uptake and accumulation characteristics.

Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) is a cyclic amino acid, identified as a compatible solute in moderately halophilic bacteria. Exogenously provided ectoine was found to stimulate growth of Escherichia coli in media of inhibitory osmotic strength. The stimulation was independent of any specific solute, electrolyte or nonelectrolyte.