INVOLVEMENT OF THE CELL-ENVELOPE OF LISTERIA-MONOCYTOGENES IN THE ACQUISITION OF NISIN RESISTANCE

The involvement of the cell wall in the acquisition of nisin resistanc e by Listeria monocytogenes F6861 and its nisin-resistant mutant was i nvestigated. Results indicated that without a cell wall, the acquired nisin resistance of the mutant was lost. Cell surface hydrophobicity w as shown to correlate with nisin sensitivity; the wild type strain bei ng more hydrophobic than its mutant, The possible role of S-layer prot eins in nisin resistance was investigated, Examination of strains by f reeze-etching and atomic force microscopy did not demonstrate the pres ence of S-layers in either strain while SDS-PAGE following S-layer ext raction procedures revealed no major protein bands. Chloramphenicol di d not adversely affect the frequency of isolation of nisin-resistant m utants, indicating that de novo protein synthesis was not involved, Th e involvement of other cell surface components, teichoic and lipoteich oic acids, was also examined. In contrast with other reports, comparis on of the total phospholipid content of the mutant with its parental s train showed no significant difference (P > 0.05).