NISIN RESISTANCE IN LISTERIA-MONOCYTOGENES ATCC-700302 IS A COMPLEX PHENOTYPE

Nisin resistance in Listeria monocytogenes ATCC 700302 is a complex ph enotype involving alterations in both the cytoplasmic membrane and the cell wall and a requirement for divalent cations, In addition to a lo wer ratio of C-15 to C-17 fatty acids than in the wild-type strain (A. S. Mazzotta and T. J. Montville, J. Appl. Microbiol. 82: 32-38, 1997), this nisin-resistant (Nis(r)) strain contained significantly more zwi tterionic phosphatidylethanolamine and less anionic phosphatidylglycer ol and cardiolipin. The extraction of cardiolipin was enhanced by a pe nicillin-lysozyme step to disrupt the cell wall. This study is the fir st to quantify the phosphatidylethanolamine component of the L. monocy togenes cytoplasmic membrane. While these cytoplasmic membrane changes were induced by nisin, the Nis(r) strain also showed altered sensitiv ities to cell wall-acting compounds, even when grown in the absence of nisin, suggesting a constitutive alteration in the strain's cell wall . A model which integrates the roles of the cell membrane, cell wall, and divalent cations is presented. Finally, nisin resistance in L. mon ocytogenes ATCC 700302 conferred cross-resistance to the class IIa bac teriocin pediocin PA-1 and the class IV leuconocin S.