Bacteria starved for prolonged periods develop increased protection against lethal temperatures

Enteric bacterial pathogens may undergo severe stresses in aquatic environments. In other respects, these bacteria share an oral route of infection and have to cross the gastric barrier to cause disease in human hosts. Considering the cross-protection against environmental stress, i.e. heat, acid and oxidation, induced by osmotic shock and nutrient starvation, the ability of various enterobacteria, including species of Escherichia, Shigella, Salmonella, Klebsiella and Yersinia, to acquire resistance to the acidic conditions encountered in the stomach (pH 2,5 for 2 h) after incubation in oligotrophic fresh or seawaters was examined. Acid resistance of E. coli, shigellae and Salmonella typhimurium was enhanced by a hundred to a hundred millions times after 100 min in seawater. This effect was also observed when cells were incubated in distilled water and phosphate buffers with low or high osmolarity. It is therefore not specific to seawater. Acid resistance was, however, 2 to 4 times higher in seawater. Acquired resistance depended on the growth phase of the cells. It was lost by subculturing the cells and proved partly dependent on rpoS and on de novo protein synthesis. A similar induced acid resistance was observed in faecal coliforms from human faeces and wastewater. The increased levels of surviving acid-resistant, enteric pathogens in natural waters may have sanitary and epidemiological implications. and Salmonella typhimurium develop adaptative responses to salt [7], heat [38], peroxides [11], acid [3,14] and nutrient starvation [33,40] generally related to the synthesis of stress proteins. To some extent, adaptation to a given stress increases tolerance to other environmental stresses [32]. Several or factors regulate the expression of survival genes, and the alternative ~r factor RpoS very likely plays a central role in cross protection [31,34]. Although rpoS is specifically regulated by carbon starvation in E. coli, rpoS mutants exhibit a higher sensitivity to a SSDI 0168-6496(94)00023-P

Section: Discussionsupporting

confidence: 71%

Effect of a short period of starvation in oligotrophic waters on the resistance of enteric bacterial pathogens to gastric pH conditions

Gauthier

1994

“…On the other hand, the maximum level of 192 protection against heat in Vtbrio sp. strain DW1 was also reached within 2 h of starvation [26], but without significant induction of synthesis of the stress proteins at that time (Fig. 4C).…”

Section: Discussionmentioning

confidence: 94%

“…The exact positions of the induced proteins were verified by Western Blot analysis. When the different Vibrio strains and an E. coli strain (Sc122) were exposed to carbon starvation, the rate of protein synthesis decreased with about 90% [25,26] and hence an induction of a starvation responder can easily be observed on a onedimensional SDS-PAGE. The induction of the stress proteins was studied in heat-shocked cells, growing cells and cells starved for 0, 0.5, 3, 24 and 96 h. Mid log phase cells and cells at the onset of the starvation period were taken as reference points.…”

Section: Discussionmentioning

confidence: 99%

“…Given the presumed role of DnaK and GroEL as molecular chaperones, it is of interest to attempt to correlate their induction with the appearance of general stress resistance. It is well established that mutants lacking functional DnaK in E. coh are impaired in survival after exposure to heat shock, cold shock, osmotic shock, oxidative stress and carbon starvation [8,[24][25][26][27][28][29][30][31][32]. The carbon starvation induced cross-protection against a variety of stress conditions in the Vibrio strains included in this study may be dependent on DnaK.…”

Section: Discussionmentioning

confidence: 99%

“…It has also been demonstrated that the cross-protection against heat offered by E. coli (Sc122) and Vibrto sp. strata DW1 cells starved for 48 h is not dependent on protein synthesis [26]. Jenkins et al [30] suggested that DnaK in E. coli does not play a role in the development of stress resistance in the initial phase of carbon starvation.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

The induction of stress proteins in three marine Vibrio during carbon starvation

Holmquist

Jouper-Jaan

Weichart

et al. 1993

The induction of DnaK and GroEL homologous proteins by heat‐shock and long‐term carbon starvation was studied in Vibrio vulnificus, Vibrio sp. strain S14, and Vibrio sp. strain DW1. In each Vibrio strain one protein (60 kDa) reacted with antibodies against Escherichia coli‐GroEL and two proteins, DnaK (69 kDa) and Sis1 (62‐60 kDa), reacted with antibodies against E. coli‐Dnak. The carbon starvation elicited induction of the stress proteins was strain‐specific, suggesting that the induction of stress proteins like DnaK and GroEL in marine Vibrios might not be a uniform starvation response. It appears as of these proteins, only DnaK in Vibrio sp. strain S14 remains induced after long‐term carbon starvation in the three marine bacterial strains that were tested.

Long-term oxidant deficiency in Pseudomonas aeruginosa PAO303 results in cells which are non-culturable under aerobic conditions

Binnerup

1993

The effect of long-term energy starvation (lack of electron acceptor in respiration) on the culturability of Pseudomonas aerugmosa PAO303 was studied by subsequent incubations for growth on aerobic or anaerobic media. A batch culture was grown on O2-free citrate minimal medium containing NO~-as oxidant. Stationary phase was reached when NO~-was exhausted. This was followed by a rapid loss of cell culturability as tested by aerobic growth on agar plates (colony forming units, cfu) or on 0.2 /~m membrane filters (epifluorescence technique) using the citrate minimal medium. However, energy-starved cells could form ten times more colonies when incubated anaerobically with NO~ (denitrifying condiUons) than when incubated aerobically. Hence the energy starvation resulted in a subpopulatlon of cells, which were detectable under denitnfymg, but not under aerobic growth conditions.