Gradual and Step wise Halophilization Enables Escherichia coli ATCC 8739 to Adapt to 11% NaCl.

Citation: Goh, DJW, How, JA, Lim, JZR, NG, WC, Oon, JSH, Lee, KC, Lee, CH, Ling, MHT. 2012. Gradual and Step-wise Halophilization Enables Escherichia coli ATCC 8739 to Adapt to 11% NaCl. Electronic Physician 4(3): 527-535.

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E. coli is a non-halophilic microbe and is used to indicate faecal contamination. Salt (sodium chloride, NaCl) is a common food additive and is used in preservatives to counter microbial growth. Previous studies had shown that pathogenic E. coli has a higher salt tolerance than non-pathogenic E. coli. The effect of how E. coli interacts with the salt present in the human diet is under-studied. Thus, it is important to investigate this relationship. In this study, we observed the genetic changes and growth kinetics of E. coli ATCC 8739 under 3% - 11% NaCl over 80 passages. Growth kinetics was estimated by generation time, cell density and minimum inhibitory concentration (MIC) of NaCl. Our results suggested that E. coli was able to adapt from 1% NaCl to 11% NaCl with an increment of 1% NaCl per month. Our MIC results suggested that E. coli was able to grow at NaCl concentration of more than 7.5% based on the Area under Curve (AUC) from 5% at passage 44 (cultured in 5% NaCl) to 13% at passage 72 (cultured at 7% NaCl). We conclude that E. coli ATCC 8739 can be adapted to grow in 11% NaCl by incremental adaptation.