Changes associated with cell membrane composition of Staphylococcus aureus on acquisition of resistance against class IIa bacteriocin and its in vitro substantiation

The emergence and spread of bacteria resistant to bacteriocins would threaten the safety of using them as food preservatives. To determine the physiological characteristics of resistant strain, resistance of Staphylococcus aureus NCDC 133 against pediocin, a class IIa bacteriocin, was isolated. A significant amplification in unsaturated fatty acid and hydroxy fatty acid in addition to branched chain fatty acid was observed in resistant which validates enhanced fluid membrane of resistant strain. Increased membrane fluidity leads to unstable oligomerization of bacteriocin which ceases pore formation. The composition of the phospholipids in resistant strain also differed from those in the wild-type strain. The putative zwitterionic amino-containing phospholipid in the resistant significantly increased, whereas amounts of amino-lacking phospholipids decreased which could be correlated to reduced negative charge making bacteriocin unable to associate optimally with bacterial membrane. Increased percent colorimetric response in resistant variant indicates that bacteriocin was positioned predominantly at the lipid-water interface rather than penetrating deep inside. Both physiological study and in vitro results confirm membrane changes during resistance acquisition which could be utilized to establish structure activity relationship and henceforth to develop potent peptide with suitable amino acid substitutes with enhanced stability and activity features.