The effects of different environmental factors (nutrient deprivation, hyper
osmotic shock, exposure to light) on enteric bacteria which have been trans
ferred into the marine environment, have been studied experimentally (micro
cosms) by considering demographic, physiological and genetic responses in E
scherichia coli or Salmonella typhimurium populations. Short-term experimen
ts (less than or equal to 48 h) showed that nutrient deprivation induced li
mited changes in measured bacteriological variables, but when combined with
hyperosmotic shock, it results in an energy charge decrease and inactivati
on of membrane transport. Light exposure mainly affects the colony-forming
capacity of bacterial populations. Combining different stress factors confi
rmed the rapid appearance of a viable, but nonculturable state (VBNC) in po
pulations of E. coli and S. typhimurium. It has been shown that cellular fo
rms other than those previously described in the literature can be generate
d following incubation in seawater. It was also established that pre-adapta
tion phenomena may occur, leading to better survival (e.g. pre-incubation i
n seawater in darkness enhanced survival under light exposure). An explanat
ion concerning these phenomena can be found by looking at the rpoS gene whi
ch controls the expression of numerous genes and can trigger a general anti
-stress response under different adverse conditions. Although the results p
rovide better comprehension of the fate of enteric bacteria in the marine e
nvironment, they also raise numerous questions related to fundamental and a
pplied problems, given in the conclusion of this paper. (C) Elsevier, Paris
.