Novel Anti-Microbial Peptide from an Environmental Rare Actinobacterium

Abstract

Rampant overuse and misuse of antibiotics in humans and poultry/livestock is leading to worldwide and rapid emergence of Multi drug-resistant (MDR) and Extensively Drug Resistant (XDR) superbugs including ESKAPE pathogens. Also, there has been a void of several years in antibiotic discovery. Thus, discovering novel therapeutic compounds is the need of the hour. Bioactive therapeutic compounds from actinobacteria include front line antibiotics and anticancer drugs. Many screening programs are directed towards isolation of bioactive compounds from these organisms but the chances of finding novel antimicrobial leads among common actinobacteria are fast dwindling. As a result, the focus has shifted to the members of less exploited genera of rare actinobacteria.

During a screening program for bioactive natural products, a rare actinobacterium was isolated from soil. The isolate was identified as Kocuria kristinae by VITEK2 microbial identification system as well as 16S rRNA gene sequencing. The organic extract of Kocuria kristinae fermentation broth was found to be active against both gram negative and gram positive organisms. The nature of bioactive compound was ascertained to be protein by qualitative tests. The protein was obtained by various protein precipitation methods and was purified by preparative TLC. The purified peptide was found to be bioactive against Serratia marcescens and showed a potent Quorum quenching activity at sublethal concentration. The peptide was characterized by UV-Vis, IR and HRMS. It was found to be similar to but significantly different than kocurin which has been previously reported from Kocuria palustris. However, this is the first report of an antimicrobial peptide (AMP) from Kocuria kristinae and can be taken up in a drug development program in the future. A quorum quenching compound like this AMP can hence attenuate the virulence of the pathogens without challenging their growth, thereby preventing the emergence of drug-resistant strains.

Keywords: Multi drug-resistant (MDR), ESKAPE, actinobacteria, VITEK2, Quorum quenching, antimicrobial peptide (AMP)