Increased d-alanylation of lipoteichoic acid and a thickened septum are main determinants in the nisin resistance mechanism of Lactococcus lactis

Abstract

Nisin is a post-translationally modified antimicrobial peptide produced by Lactococcus lactis which binds to lipid II in the membrane to form pores and inhibit cell-wall synthesis. A nisinresistant (Nis R ) strain of L. lactis, which is able to grow at a 75-fold higher nisin concentration than its parent strain, was investigated with respect to changes in the cell wall. Direct binding studies demonstrated that less nisin was able to bind to lipid II in the membranes of L. lactis Nis R than in the parent strain. In contrast to vancomycin binding, which showed ring-like binding, nisin was observed to bind in patches close to cell-division sites in both the wild-type and the Nis R strains. Comparison of modifications in lipoteichoic acid of the L. lactis strains revealed an increase in D-alanyl esters and galactose as substituents in L. lactis Nis R , resulting in a less negatively charged cell wall. Moreover, the cell wall displays significantly increased thickness at the septum. These results indicate that shielding the membrane and thus the lipid II molecule, thereby decreasing abduction of lipid II and subsequent pore-formation, is a major defence mechanism of L. lactis against nisin.

CpsY Influences Streptococcus iniae Cell Wall Adaptations Important for Neutrophil Intracellular Survival

“…These systems can activate enzymes that allow the bacteria to decorate both the cell membrane and cell wall with various chemical modifications. For example, lipid lysinylation of the cellular membrane by MprF (23,44,61,70,77) and D-alanylation of wall teichoic acids by the DltABC locus (15,24,39,41,43,64) provide protection from cationic antimicrobial peptides. Resistance to lysozyme occurs through PG acetylation of MurNAc residues by the OatA O-acetyltransferase found in Gram-positive organisms (3,4,19,34,80) or the PatA/PatB system in Gram-negative organisms (56).…”

Activity and Export of Engineered Nisin-(1-22) Analogs

“…Studies on the activity of truncated nisin mutants showed that nisin-(1-32)-NH 2 , nisin-(1-29) and nisin- (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) have respectively slightly higher, about 10-fold lower and 100-fold lower activity than nisin [9]. Rink et al found that nisin-(1-22) has only 10-fold lower activity than nisin and suggested that the positively charged Lys22 might enhance binding to the negatively-charged bacterial membrane [8].…”

“…An interesting candidate antibiotic is the antimicrobial peptide nisin A ( Figure 1) [1]. Although nisin has been widely used for a long time as a food-preservative in a broad range of products [2,3], resistance is limited [4,5]. Nisin is produced by Lactococcus lactis and exerts antimicrobial activity against a broad range of Gram-positive bacteria.…”

Effect of Nisin on Technological and Microbiological Characteristics of Stirred Yoghurt

“…Antibacterial mechanisms of nisin may be due to passage through cell wall and interaction with lipid II [8,9]. Nisin was inhibitory to both Streptococcus thermophilus and Lactobacillus delbrueckii subsp.…”