Escherichia coli, a constitutive microflora of mammalian guts, was originally thought to be able to live only in the enteric environment. As such, the occurrence of E. coli in water and food has been used as an indicator of fecal contamination, signaling the possible presence of fecal pathogens. However, recent reports have indicated that E. coli can be found in many different types of external habitats (e.g. seawater, sediment and soil) independent of fecal input. Once exposed to the external environment, E. coli will encounter various stresses that are not present in the animal hosts. One of immediate impact to E. coli cells entering the marine environment is the high salinity of seawater. Although the physiology, genetics and biochemistry of E. coli have been intensively stud...[ Read more ]

Escherichia coli, a constitutive microflora of mammalian guts, was originally thought to be able to live only in the enteric environment. As such, the occurrence of E. coli in water and food has been used as an indicator of fecal contamination, signaling the possible presence of fecal pathogens. However, recent reports have indicated that E. coli can be found in many different types of external habitats (e.g. seawater, sediment and soil) independent of fecal input. Once exposed to the external environment, E. coli will encounter various stresses that are not present in the animal hosts. One of immediate impact to E. coli cells entering the marine environment is the high salinity of seawater. Although the physiology, genetics and biochemistry of E. coli have been intensively studied, it remains unknown that how the bacterium survive in the external habitats. Previous studies also showed that E. coli exhibited considerable intraspecies genomic variation, which suggested that the organism was capable of adapting to different ecological niches. In this study, we investigate the tolerance of 160 fecal E. coli isolates to different salinity levels so as to understand the intra-specific variations in such stress resistance. After that, we used transcriptomic and proteomic analysis to unravel the methods that E. coli isolates of different genetic background use to overcome salinity stress. Different proteomic and transcriptomic profiles of different E. coli isolates revealed that during growth under different salinity conditions, several metabolic processes were involved in overcoming osmosis stress. Elucidating the global adaptive response of different E. coli isolates during exposure to different salinity stress has provided more information of the physiology of this bacterium when facing high salinity stress of marine environment.