Variations in the membrane fatty acid composition of resistant or susceptible Leuconostoc or Weissella strains in the presence or absence of Mesenterocin 52A and Mesenterocin 52B produced by Leuconostoc mesenteroides subsp. mesenteroides FR52.

Mesenterocins 52A (Mes52A) and 52B (Mes52B) are antimicrobial peptides produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52. Mes52A is a class IIa bacteriocin of lactic acid bacteria with a broad spectrum of activity. Mes52B is an atypical class II bacteriocin with a narrow spectrum of activity. Four Leuconostoc and Weissella wild-type strains were selected for their susceptibility or insensitivity to these mesenterocins. Four strains resistant to Mes52A or Mes52B were generated from the three susceptible wild-type strains by increasing bacteriocin concentrations in culture media. These resistant strains were at least 30 times more resistant than the wild-type strains. No cross-resistance to Mes52A and Mes52B was observed in these strains. No significant differences in membrane fatty acid composition were observed among the three susceptible wild-type strains and the four resistant strains cultured in MRS broth. Thus, the mesenterocin resistance is unlikely to be due to changes in membrane fatty acid composition. When cultured with Mes52A or Mes52B, the membranes of insensitive and resistant strains contained more saturated fatty acids (1 to 10% more) and less unsaturated fatty acids (3 to 6% less), resulting in a more rigid membrane. Thus, the presence of mesenterocin in the culture media of insensitive or resistant strains induced a significant increase in saturated fatty acid contents and a decrease in unsaturated fatty acid contents. Weissella paramesenteroides DSM 20288BR, resistant to Mes52B, responded atypically, probably due to the production of an inhibitor.