High hydrostatic pressure influence on viability and mutagenesis of Salmonella Typhimurium

Abstract

Background: pressure is a well-known physical environmental parameter. Nevertheless, the basic principles of microbial survival under high hydrostatic pressure (HHP), especially genetic response to pressure, are still poorly understood. The purpose of this study was to investigate the influence of HHP ranging from 50 to 800 MPa on viability and mutagenesis of Salmonella typhimurium. Materials and methods. The standard plate count method (counting the total number of colony forming units (CFUs) on the plate) and the propidium iodide (PI) flow cytometric assay were used to determine the bacterial viability after HHP treatment. Ability of HHP to induce gene mutations was examined by the Ames assay employing Salmonella typhimurium TA100 and TA98. Results. The results obtained showed that survival of S. typhimurium cells considerably decreased when bacteria were exposed to a pressure of 200 MPa and above. Herewith, the survival index calculated according to the total number of CFUs was up to six orders of magnitude lower than that obtained by the flow cytometric analysis under the same HHP. This fact can be explained by the entrance of the some part of bacterial population into the viable but nonculturable (VBNC) state. The pressure of 50 MPa was found to cause a 1.9-fold increase in the number of His+ revertants of S. typhimurium TA98 in Ames test. Conclusion. Our results demonstrate that HPP of 200 MPa and above significantly inhibits the viability of S. typhimurium cells as well as triggers the induction of VBNC state. The results of Ames test suggest that HHP of 50 MPa can induce gene mutations in bacterial cells. The possible mechanisms of HHP effects on cells viability as well as genetic response of bacteria under HHP are discussed.

Keywords

Salmonella typhimurium / high hydrostatic pressure / Salmonella typhimurium / viability, viable but nonculturable state, mutagenesis, Ames assay

RIGHTS & PERMISSIONS

Karamova N.S., Zelenikhin P.V., Kiselev V.D., Lipatnikova A.A., Ilinskaya O.N.