Effect Of Glycine Betaine And Molecular Chaperone Dnak On The Tolerance To Nacl Of Tetragenococcus Halophilus CICC10469

Tetragenococcus halophilus CICC10469with a high-salinity resistance was isolatedfrom the traditional soy sauce koji'. To explore the correlation between salt-tolerance andaccumulation of compatible solute as well as the property of molecular chaperone Dnak, andcompared with non-halophilic (salt-sensitive) lactic acid bacteria Lactococcus lactis MG1363,and then found its special active substances or metabolic pathways. Firstly, the effects ofNaCl on growth of T. halophilus CICC10469and Lactococcus lactis MG1363weremonitored by measuring growth curve in different NaCl concentrations. The main compatiblesolute and its variation with the change of NaCl concentration were detected by TLC,HPLCand NMR. The influence of NaCl on the expression of molecular chaperone Dnak wasdetected by real-time Quantitative PCR, and finally, the relationship between the solubleprotein content and concentration of NaCl was measured, so that analyzing possible factorswhich affect the strain's performance of salt resistance.Results showed that T. halophilus CICC10469can grow well in MRS medium thatcontain4%-16%NaCl concentration, which could accumulate glycine betaine as the maincompatible solute. Under the conditions that the bacteria could grow well, there was a positivecorrelation between NaCl concentration in the environment and the accumulation of glycinebetaine, the expression of molecular chaperone DnaK, as well as the amount of intracellularsoluble proteins. Particularly, the expression of DnaK in salt-sensitive lactic acid bacteria L.lactis MG1363was more than in T. halophilus CICC10469.However, when NaClconcentration reached or exceeded20%, the strains could not grow well, and the amounts ofall these substances were declined, indicating that the bacteria hardly make necessaryadjustments depending on the outside environment, some of proteins'biosynthetic pathwaywere inhibited.From these observations, it can be inferred that compatible solute glycine betaine andmolecular chaperone DnaK played a very important role in T. halophilus' halophilic process.The ability of rapid synthesis and release of glycine betaine as well as strong activity ofmolecular chaperone DnaK may attribute to salt-tolerance for T. halophilus CICC10469.