Antibacterial potential of Juglomycin A isolated from Streptomyces achromogenes, an endophyte of Crocus sativus Linn.

To evaluate the antimicrobial potential of Juglomycins isolated from Streptomyces achromogenes E91CS4, an endophyte of Crocus sativus Linn.

The extract from E91CS4 displayed significant antimicrobial activity against several pathogens. The endophyte was identified as Streptomyces achromogenes on by 16S ribosomal gene analysis. Chemical investigation of the extract led to the isolation of two naphthoquinone antibiotics, Juglomycin A and B. Juglomycin A inhibited several pathogens, with an MIC value of 13.7µg ml^-1 while it was most potent against Escherichia coli, Bacillus thuringiensis and Xanthobacter flavus with MIC values of 6.8, 3.4 and 6.8 µg ml^-1 , respectively. It was found to reduce the biofilm formation in E. coli through inhibition of swimming and swarming motilities and down-regulation of fimH gene. The α-haemolysin related gene (hlyA) was also down-regulated indicating that the compound is also reducing the virulence in E. coli. In vitro time kill kinetics showed efficient bactericidal activity of this compound. Further, Juglomycin A inhibited bacterial transcription/translation in vitro, while also inducing post-antibiotic effect in E. coli.

Juglomycin A is a potential antimicrobial compound against several bacterial pathogens, particularly, E. coli.The current study showed the promising potential of Juglomycin A as an antimicrobial agent. Efforts should be made to scale up the production of this compound and conduct further studies to explore its efficacy as an antibiotic, using in vivo models.