Survival of Escherichia coli and Acinetobacter junii at various concentrations of sodium chloride

Abstract

The survival of two heterotrophic bacteria in conditions of various concentrations of NaCl was tested. Both bacteria can commonly enter marine environments through sewage or wastewater treatment plant effluents; the Escherichia coli is a common enteric bacterium and Acinetobacter junii is a phosphate-accumulating bacterium inhabiting activated sludge. When cultivated in nutrient rich media (COD 8700 mg O 2 L -1 ), both bacteria were multiplying during 72 h at concentrations of NaCl up to 5% for E. coli and 3.5% for A. junii. Total die-off of E. coli was detected at 72 h by NaCl concentration of 20%. Total die-off of A. junii was detected at 72 h by NaCl concentration of 10%. When the same bacteria were cultured in nutrient depleted media (COD 90 mg O 2 L -1 ), the multiplication of E. coli stopped at 3.5% of NaCl and higher, but the cells were able to survive for longer period of time at extreme NaCl concentrations of 20 and 30%. The negative influence of NaCl to A. junii was pronounced in conditions of organic matter shortage and rapid die-off was observed at 3.5% of NaCl and higher. Both bacteria seemed to be osmotolerant when cultured in nutrient-rich media, but not in nutrient-depleted media.

Survival and growth rate of coastal water <i>Escherichia coli</i> isolates in different salt concentrations

“…In this study, the five E. coli isolates showed salt tolerance of up to 6%, this corroborates earlier studies were strains of E. coli had been able to grow on salt concentrations of between 0 and 8% (Brewer, 2000;Vera and Stojanović, 2003;Hrenovic and Ivankovic, 2009). The ability of these isolates to show significant growth in sodium chloride concentrations up to 6% can possibly be because the bacteria were grown in a nutrient rich media, where the effect of NaCl was hindered.…”

“…There is a possibility of NaCl ions binding to organic matter in the growth medium which could consequently reduce the negative influence of the NaCl to the bacteria as opposed to when the organisms are grown in nutrient deficient media and growth is obviously inhibited. In addition, the growth rate of bacteria in a nutrient rich medium is independent of the concentrations of nutrient, but in a nutrient limiting environment, growth rate is directly proportional to the extracellular concentration of the limiting nutrient (Warry et al, 2008;Hrenovic and Ivankovic, 2009). As had earlier been shown by Goh et al (2012) that E. coli can easily adapt to high salt concentrations, the isolates in this study also demonstrated rapid adaptation with the first two isolates Ec1 and Ec2 showing a short lag phase of growth during the first hour of incubation (Figure 2A and 2B) while the other three isolates particularly Ec3 and Ec4, showed obvious increase in optical density during the initial incubation period ( Figure 2C, D and E) since observable lag phase was noted.…”

“…Nevertheless, it is noteworthy that apart from salinity, other factors such as nutrient availability, microbial antagonism and antibiotic substances creates limiting environmental conditions which affect the survival of enteric bacteria in the aquatic ecosystem (Warry et al, 2008;Hrenovic and Ivankovic, 2009). Moreover, the presence of nutrients and osmotic compounds in coastal areas help fecal bacteria to survive and tolerate salinity (Pommepuy et al, 1992).…”

Identification and biotechnological potential of psychrotrophic marine isolates

“…Earlier, Hrenovic and Ivankovic (2009) have demonstrated the effect of NaCl concentrations on growth of E. coli and Acinetobacter jejuni isolated from polluted water and activated sludge respectively. The authors attributed osmotolerance not only to the concentration of NaCl, but also to shortage of nutrients.…”

Adaptation of Escherichia coli ATCC 8739 to 11% NaCl

“…e viable count dropped progressively with further increase in concentration suggesting that E. coli is nonhalophilic and 7% NaCl is bacteriostatic. Hrenovic and Ivankovic [10] reported that the growth of E. coli is optimal below 5% NaCl. e adaptation of E. coli to salt may suggest similar resistance to other preservatives and its ability to grow in saline environment may be underestimated.…”