Isolation of Actinomycetes from Arachis hypogaea L. and Gossypium herbaceum L. for Screening Antibacterial and Antifungal Activities

The principal objective of the present study was to check the antimicrobial activity of Actinomycetes isolated from soil samples collected from the fields of Arachis hypogea L. and Gossipium herbaceum L. against different plant pathogenic strains. Various soil samples were isolated from fields located near the Junagadh district, Gujarat, India. Isolation was followed by a serial dilution process which was later plated on Actinomycete Isolation Agar (AIA) media. Potential colonies were subjected to screening, purification, and storage in glycerol stock. Morphological and Biochemical characterization of the isolates was performed. Isolated candidates were subjected to extraction for the production of the antimicrobial compound. The antimicrobial activity of the purified extract of isolates was tested. Total 30 actinomycete isolates were evaluated for antagonistic activity against pathogenic microorganisms.

Isolates C-25, C-15, and G-1 showed the best results in the decreasing order of their potency against fungal pathogens, and C-5, C-25, C-14, and C-13 showed the best results in decreasing order of potency against bacterial pathogens. 3 isolates inhibited all 4 test fungi. 10 isolates inhibited 3 test fungi. 11 isolates inhibited 2 test fungi. 6 isolates did not inhibit any test fungi. 4 isolates show potent inhibition. 15 inhibited Macrophomina. C-10 showed a 1 cm inhibition zone & G-1 showed a 0.8 cm zone of inhibition. 12 isolates gave 0.2-0.6 cm zone and 15 isolates gave negative results against Macrophomina. C-10 showed a very potent zone of inhibition of 0.7 cm. 9 isolates showed a 0.1-0.5 cm zone of inhibition. 20 isolates did not show inhibition against Fusarium. 1 isolate C-11(a) gave the 1cm potent zone of inhibition. 15 isolates gave the 0.7-0.2cm inhibition of the growth. 14 isolates gave negative results against Alternaria fungus. From these results, it was concluded that isolates had antibacterial and antifungal activities and could be used in the development of new antibiotics for pharmaceutical or agricultural purposes.