Influence of osmoregulation processes on starvation survival of Escherichia coli in seawater

Abstract

The adaptation of enteric bacteria in seawater has previously been described in terms of nutrient starvation. In the present paper, we bring experimental arguments suggesting that survival of these microorganisms could also depend on their ability to overcome the effects of osmotic stress. We analyzed the influence of osmoregulatory mechanisms (potassium transport, transport and accumulation of organic osmolytes) on the survival of Escherichia coli in seawater microcosms by using mutants lacking components of the osmotic stress response. Long-term protection was afforded to cells by growth in a medium whose osmotic pressure was increased by either NaCl, LiCl, or saccharose. Achievement of the protection state depended at least partly on osmoregulatory mechanisms, but differed when these were activated or induced during prior growth or in resting cells suspended in phosphate buffer or in seawater. When achieved during growth, K+ transport, glycine-betaine (GBT) synthesis or transport, and trehalose synthesis helped increase the ability to survive in seawater. Protection by GBT was also obtained with resting cells in a phosphate buffer at high osmotic pressure. However, when added only to the seawater, GBT did not change the survival ability of cells no matter what their osmoregulation potential. These results showed that the survival of E. coli cells in seawater depends, at least partly, on whether they possess certain genes which enable them to regulate osmotic pressure and whether they can be stimulated to express those genes before or after their release into the environment. This expression requires nutrients as the substrates from which the corresponding gene products are made.

Bacteria starved for prolonged periods develop increased protection against lethal temperatures

“…Several studies have also addressed the ability of E. coil cells to survive in sea-water [19,20] and to resist other forms of stress [6]. The survival of E. coli in sea-water seems to be strain dependent and the ability to survive is related to the ability to osmoregulate [21]. The difference in the long term survival potential between the two E. coli strains, Sc122 and K165 (Fig.…”

Survival of enteric bacteria in seawater

“…When released into the sea, enteric bacteria are subjected to an immediate osmotic upshock, and their ability to overcome this by means of several osmoregulatory systems could largely in£uence their subsequent survival in the marine environment [24,47].…”

Microbial growth and resuscitation alter community structure after perturbation

“…Preliminary results of growth experiments at 4" C, indicate that some isolates recovered only after storage double at rates which cannot account for the numbers of these cells after storage. Others have suggested that temperature, nutrient level and osmotic changes were responsible for the increased culturability of VNBC cells [13][14][15][16]301. In this study, an entire cluster of organisms related to Arthrobacter was cultured only after storage at 4" C ( Fig.…”

“…VBNC bacteria are present in many natural environments [lo-131, and certain conditions may aid the resuscitation of these dormant bacterial cells, thereby increasing recovery. Enrichment methods for VBNC bacteria include the use of media with low nutrient concentrations [14], liquid media [ll], the addition of specific metabolites [15], and osmotic or temperature shock [13,16]. Perturbations that occur during sampling and sample handling may result in such enrichment conditions.…”