Expression of Lactobacillus pentosus B96 bacteriocin genes under saline stress.

This research studied the influence of sodium chloride on bacteriocin activity of table olives' strain Lactobacillus pentosus B96. The strain was cultured in MRS under different NaCl concentrations (0, 4, 6 and 8%, in w/v). In MRS, maximum bacteriocin activity was achieved 9 h later. A medium containing 4 or 6% NaCl (w/v) increased the total bioactivity of the strain and an 8% NaCl reduced it. Real-time PCR was used to monitor the genetic expression of the bacteriocin genes plnA, plnB, plnC, plnE/F, plnJ, plnK, plnN and plantaricin S. Cultured in MRS, plantaricin S reached its maximum expression during the lag phase while plnE/F expresses during the exponential phase. The presence of sodium chloride in the medium moved the maximum expression of plantaricin S to the stationary phase, independently of the concentration. 4% (w/v) of NaCl didn't affect the expression pattern of plnE/F while promotes the expression of plnN during both the lag and the exponential phases. More sodium chloride, 6% (w/v) maintained the expression of plnN in the pag phase but not in the exponential and moved plnE/F expression to the stationary phase. Plantaricin S, plnE/F and plnN over-expressed during the stationary phase in the higher sodium chloride concentration assayed, 8% (w/v). The relative expression level of plsA was 1000-fold higher than that of the plnE/F and plnN genes and even the ldhD constitutive gene used. Under our conditions, expression of plnA, plnB, plnC, plnJ and plnK genes was not observed.