Heat resistance of viable but non-culturable Escherichia coli cells determined by differential scanning calorimetry

• Published in: FEMS microbiology letters Vol. 364; no. 19
• Main Authors: Castro-Rosas, Javier, Gómez-Aldapa, Carlos Alberto, Villagómez Ibarra, José Roberto, Santos-López, Eva María, Rangel-Vargas, Esmeralda
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 16.10.2017
• Subjects: Bacteria; Calorimetry; Calorimetry, Differential Scanning - methods; Coliforms; Differential scanning calorimetry; E coli; Ecological monitoring; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - growth & development; Heat measurement; Heat resistance; Heat transfer; Hot Temperature; Microbial Viability; Microbiology; Seawater; Thermal resistance; thermal resistance; viable but non-culturable state; differential scanning calorimetry; Escherichia coli
• ISSN: 1574-6968; 0378-1097; 1574-6968
• DOI: 10.1093/femsle/fnx188

Abstract Several reports have suggested that the viable but non-culturable (VBNC) state is a resistant form of bacterial cells that allows them to remain in a dormant form in the environment. Nevertheless, studies on the resistance of VBNC bacterial cells to ecological factors are limited, mainly because techniques that allow this type of evaluation are lacking. Differential scanning calorimetry (DSC) has been used to study the thermal resistance of culturable bacteria but has never been used to study VBNC cells. In this work, the heat resistance of Escherichia coli cells in the VBNC state was studied using the DSC technique. The VBNC state was induced in E. coli ATCC 25922 by suspending bacterial cells in artificial sea water, followed by storage at 3 ± 2°C for 110 days. Periodically, the behaviour of E. coli cells was monitored by plate counts, direct viable counts and DSC. The entire bacterial population entered the VBNC state after 110 days of storage. The results obtained with DSC suggest that the VBNC state does not confer thermal resistance to E. coli cells in the temperature range analysed here. The VBNC state do not confer thermal resistance to Escherichia coli cells in the temperature range analysed here.