An in vitro antimicrobial activity of Beauveria bassiana secondary metabolites

Abstract

Fungi are organisms that provide various environmental services. Beauveria (B.) bassiana (Order: Hypocreales, Family: Cordycipitaceae) is an example of an entomopathogenic fungus developed and used for many agricultural, biomedical, and medicinal purposes. A crude extract of B. bassiana was made using a culture broth to test its antimicrobial effects against several animal pathogenic bacteria, comprising Klebsiella (K.) pneumoniae, Escherichia (E.) coli, and Staphylococcus (S.) aureus and fungi (Candida (C.) albicans). In 250 mL Erlenmeyer flasks, a liquid median (100 ml) was infected with 1 ml of an aqueous conidial suspension (107 conidia/ml). The flasks were incubated at 27.2°C on a rotary shaker (180 rpm) for seven days. The fermented broth was filtered to remove the biomass and obtain a crude extract of B. bassiana at various concentrations, which was later used for the disk diffusion method. Results demonstrated that the crude extracts effectively against the tested microorganisms and fungi. The B. bassiana extract showed an effect against K. pneumoniae, C. albicans, S. aureus, and E. coli with inhibition zones measuring 22, 23, 25, and 27 mm in diameter, respectively. The regression analysis indicated that each concentrate increase in B. bassiana culture filtrate showed a significant increase in the inhibition zone by 0.2342, 0.2330, 0.1909, and 0.2010 mm for the groups of S. aureus, E. coli, K. pneumoniae, and C. albicans, respectively. The amplification of the BbbsIS gene produced a single fragment of an approximate length of 156-190 bp. This study confirmed that the antimicrobial drug could be produced from B. bassiana extracts to prevent many diseases associated with microbial and fungal infections. It also developed an approach constructed by absolute PCR quantification for the expression of genes encoding the synthetase enzymes of the secondary metabolites viz., bassianolide (BbbslS), beauvericin (BbbeaS), and B-tubulin during the initial times of contagion.