Antimicrobial Profiling and Molecular Identification of Alternaria arborescens CLB12, A Myco-endosymbiont Inhabiting Combretum latifolium Blume

Abstract

Fungal endosymbionts are currently driving the therapeutic use of antimicrobial drugs to combat multi drug resistant infections. An endosymbiotic strain CLB12 was isolated from the root tissue of Combretum latifolium Blume (Combretaceae) collected from the Western Ghats of Southern India. Strain CLB12 was then identified as Alternaria arborescens by its characteristic cultural morphology with ITS rDNA and intervening 5.8S rRNA gene sequence. Antimicrobial profiling of ethyl acetate fraction of CLB12 was performed by disc diffusion method. Secondary metabolites produced were effectively inhibited a panel of test human pathogens including Pseudomonas aeruginosa (12.66 ± 0.33 mm), methicillin-resistant Staphylococcus aureus (12.33 ± 0.33 mm), Bacillus subtilis (16.66 ± 0.33 mm) and Candida albicans (12.00 ± 0.57 mm). TLC-bioautography assay confirmed the presence of antimicrobial compound as depicted by zone of inhibition on the intensive band. Effective inhibition of both bacterial and fungal pathogens suggests that metabolites have a broad spectrum of antimicrobial activity. The present research highlights the utility of A. arborescens CLB12 as prolific source for the biodiscovery of new antimicrobials to combat multidrug-resistant pathogens. The study also emphasizes the inter-habitat cycling of fungal endosymbiont and their possible benefits of A. arborescens to the host.