Inhibitory effects of endophytic bacterial metabolite (Gougerotin) of Ziziphus mauritiana (Ber fruit) against human bacterial pathogens

Abstract

Emergence of antibiotic resistance necessitates the discovery of novel antibiotics. Endophytic microbes reside within plant tissues without causing harm and are a promising source for novel bioactive compounds. Current study reveals the antimicrobial properties of endophytic bacterial metabolite obtained from Ziziphus mauritiana. Among the isolated bacteria, VITEMMAJ2 strain was a potent producer of the lead molecule. A significant zone of inhibition was observed in chloroform extract which was further purified by solid phase extraction and ultra performance liquid chromatography. Gas chromatography mass spectrometry and liquid chromatography high resolution mass spectrometry showed a molecular mass of 443 which corresponded to Glucopyranuronamide-1-(4-amino-2-oxo-1-(2H)-pyrimidinyl)-1,4-dideoxy-4-(D-2-(2-(methylamino) acetamido) hydracrylamido). The presence of NH_2, NH₂−CO, CH₂, CH₃, COC and CC groups in fourier transform infrared spectroscopy confirmed the functional groups of the lead molecule. Molecular characterization by 16S rRNA gene sequencing revealed VITEMMAJ2 to be the closest neighbour of Bacillus subtilis and scanning electron micrographs showed the rod-shaped morphology. Seed germination assay of the lead molecule on Vigna mungo, Vigna unguiculata and Phaseolus lunatus underscored the non-toxic nature of the compound. Endophytic bacteria of Z. mauritiana showing inhibitory effects on human bacterial pathogens have been reported for the first time in this study.