Towards improved resistance ofCorynebacterium glutamicumagainst nisin

AbstractThe bacteriocin nisin is one of the best studied antimicrobial peptides. It is widely used as a food preservative due to its antimicrobial activity against various Gram-positive bacteria including human pathogens such asListeriamonocytogenesand others. The receptor of nisin is the universal cell wall precursor lipid II, which is present in all bacteria. Thus, nisin has a broad spectrum of target organisms. Consequently, heterologous production of nisin with biotechnological relevant organisms includingCorynebacterium glutamicumis difficult. Nevertheless, bacteria have evolved several mechanisms of resistance against nisin and other cationic antimicrobial peptides (CAMPs). Here, we transferred resistance mechanisms described in other organisms toC. glutamicumwith the aim to improve nisin resistance. The presented approaches included: expression of (i) nisin immunity genesnisIand/ornisFEGor (ii) nisin ABC-transporter genes ofStaphylococcus aureusand its homologues ofC. glutamicum, (iii) genes coding for enzymes for alanylation or lysinylation of the cell envelope to introduce positive charges, and/or (iv) deletion of genes for porins of the outer membrane. None of the attempts alone increased resistance ofC. glutamicummore than two-fold. To increase resistance ofC. glutamicumto levels that will allow heterologous production of active nisin at relevant titers, further studies are needed.