Effect of Growth Conditions on Antibacterial Activity of Trichoderma harzianum against Selected Pathogenic Bacteria

Bacterial infections are prevalent in crops and humans, therefore, the need for novel and effective antibacterial compounds to treat, prevent and resist is highly demanded. Luckily fungi are potential producer of antibacterial natural products. The present study was initiated to investigate the antibacterial activity of Trichoderma harzianum against phyto and human pathogenic bacterial strains. T. harzianum was grown under different conditions and their extracts were evaluated, using disc diffusion method against tomato wilt causing bacteria (Xanthomonas campestris and Clavibacter michiganensis). Extracts that resulted in strong activity were fractionated into acetonitrile and ethyl acetate followed by testing against human pathogenic bacterial strains (Eschericia coli, Pseudomonas aeruginosa and Staphylococcus aureus) using 96 well microtitre plate method. The Ethyl acetate fraction showed maximum zone of inhibition (24.25±1.06 mm) against X. campestris and (23.15±2.12 mm) against C. michiganensis on growth nutrient broth (GNB) medium as compared to other culture media (Potato dextrose broth and yeast extract broth). Similarly maximum zone of inhibition was observed in optimized parameters like shaking flask culture, 25 °C temperature, media of pH 5 and light fermentation.The EtOAc extract exhibited the minimal value of MIC (10.41±4.50 μg/mL) against gram negative E. coli, while its acetonitrile fraction yielded (6.50±2.25 μg/mL) of MIC against S. aureus. Hence, it is revealed from the results that T. harzianumis a potential source of antibiotic drugs as it showed a wide range of bioactivity against both phyto and human pathogenic bacteria.