Immunity and Resistance Towards Bacteriocins

Three important phenotypes can confer non-sensitivity to bacteriocins (i) immunity is genetically linked with bacteriocin production and exerts the strongest level of non-sensitivity, (ii) resistance can occur as the appearance of spontaneous mutants following selection on the bacteriocin and (iii) resistance conferred by a gene that is not genetically linked with bacteriocin production. These three categories of resistance are likely to be similar for any bacteriocin [21]. 

Based on these findings, it seems that an important group of the immunity proteins exert their activity at the cytoplasmic membrane, although IciA is the only immunity protein studied in detail. The lactococcin A immunity factor was purified and shown to interact with the cell membrane, whereas the presence of free intracellular IciA is considered as a reservoir of immunity factor protein 

Recently, three additional open reading fi ames, nisF, nisE and ni G, were revealed adjacent to nisK [104]. A comparable gene cluster, epiFEG has been described for the lantibiotic epidermin, produced by Staphylococcus epi-dermidis [ 163]. The NisE/EpiE and NisG/EpiG proteins are bo A predominantly hydrophobic with six transmembrane domains [104,163]. The NisF/EpiF com- 

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