Adaptational change in proline and water content of Staphylococcus aureus after alteration of environmental salt concentration

Abstract

Adaptation of Staphylococcus aureus to a change in salinity was studied by estimating the intracellular content of water and proline after alteration of the salt concentration of the culture medium. The intracellular water content of S. aureus cultured in normal broth was 1.70 g/g (dry weight). After transfer to 1.8 M NaCl-containing broth, the water content decreased to 0.80 g/g (dry weight) within 1 min. After changing the salt concentration of the medium, intracellular free proline (assumed to be one of the osmoregulators in S. aureus) increased gradually from 0 to 1,400 umol/g (dry weight) during 30 min of incubation at 370C. The water content rose to 0.88 g/g (dry weight) in 30 min. Proline was not taken up at 0 to 40C, suggesting that the process was one of active transport. The salt tolerance of S. aureus, therefore, appears to occur initially by dehydration of the cell after transfer from a medium of low salinity to one of high salinity and then by accumulation of proline, which carries water into the cell with it. o. 3 S.A.

Physiological and genetic responses of bacteria to osmotic stress.

“…The mechanism responsible for this regulation has not been studied. However, Staphylococcus alureius can accumulate high concentrations of proline in response to osmotic stress as a result of transport but not by increased synthesis (4,125). In general, gram-negative bacteria achieve high intracellular concentrations of proline during osmotic stress only by enhanced transport.…”

Temporal Stability of the Healthy Human Skin Microbiome Following Dead Sea Climatotherapy

“…Therefore, the observed stability of the healthy human skin microbiome following DSC reflects only total community membership, and does not take into account molecular and biochemical capabilities. In addition, several culturebased studies have indicated that skin commensals are halotolerant, and therefore the microbial community may not be affected dramatically by exposure to the high salinity of the Dead Sea (30,31).…”

Microbial behaviour in salt-stressed ecosystems

“…In bacteria, until then, only amino acids like proline and glutamic acid had been suspected of serving an osmotic function. However, the few reports available were not only inconclusive, contradicting each other as to the presence of an ionic cytoplasma, but had also failed to distinguish between de novo synthesis and uptake of solutes from the growth medium [43][44][45][46]. In addition, due to analytical problems, the most common compatible solutes remained undetected and the apparent failure to meet osmotic balance led to the proposal of a hypoosmotic cytoplasm [47,48].…”