Nisin Induced Morphological Changes and Disruption Of Growth in Bacillus Subtilis

Abstract

Nisin is a 34 residue long cationic lanthionine antibiotic produced by Lactococcus lactis and known to show antimicrobial activity against a broad spectrum of gram-positive bacteria. During its antimicrobial action it is known to target intermediates in the bacterial cell wall biosynthesis, lipid II, and undecaprenyl pyrophosphate. Recent discoveries of lipid II as a target for nisin has brought nisin to the forefront, as a model case, in the battle against antibiotic resistance and assessing the combination of using conventional antibiotics with nisin remains to be explored. Here we evaluated the effect of antimicrobial activity of Nisin on Bacillus subtilis by determining the MIC (Minimum inhibitory concentration), MBC (Minimum bactericidal concentration), Zeta potential (electrokinetic potential), SEM (Scanning electron microscopy), FESEM (Field emission scanning electron microscopy) and bacterial cell viability by Baclight Fluorescencein the presence and absence of Ampicillin. We observe that increasing concentrations of Nisin drastically prolong the lag phase of Bacillus subtilis and cause excessive delay in reaching the stationary phase. The electron micrographs depict rupturing of bacterial cell membrane, significant loss of surface area and volume. Further, an interesting transformation of cylindrical B subtilis into ellipsoidal shape is observed.