Inhibition of microbial pathogens and toxicity assessment of noformicin synthesized by Psychrobacter faecalis: An endophyte of Averrhoa carambola

Abstract

Plants are known to harbor endophytic microbes which primarily reside in tissues beneath the epidermal cells. The current study was focused on exploring the endophytic bacteria of Averrhoa carambola for antimicrobial activity. The metabolites of endophytic isolate VITPMJ7 were found to be effective in cross streak method (antagonistic activity) as it inhibited the growth of Bacillus cereus and Escherichia coli. Furthermore, the effective isolate was fermented and chloroform extract showed antibacterial activity in the well diffusion method against E. coli, B. cereus and Staphylococcus aureus. Chloroform extract was fractionated and the lead molecules were obtained using solid phase extraction column (SPE) and Ultra performance liquid chromatography (UPLC). The purified lead molecule that showed inhibitory effects was identified to be noformicin by GC-MS. The presence of various functional groups such as amine, thiol, alcohol, alkene, sulfoxide identified by FT-IR supported and confirmed the lead molecule to be noformicin. The isolate VITPMJ7 capable of producing the lead compound was identified to be Psychrobacter faecalis by 16 S rRNA gene sequencing. Toxicity assessment of the metabolites in seed germination assay with Vigna radiata, Vigna mungo and Cajanus cajan revealed the non-toxic nature of the compounds.