Antifungal efficacy of bacteria isolated from marine sedentary organisms

Abstract

The antibiotic-producing ability of 57 bacteria isolated from 8 marine sedentary organisms, 6 sponges (Spirastrella sp., Phyllospongia sp., Ircinia sp., Aaptos sp., Azorica sp., Axinella sp.), 1 soft coral (Lobophytum sp.) and 1 alga (Sargassum sp.), was evaluated against 6 phytopathogenic fungi (Helminthosporium oryzae, Rhizoctonium solani, Pyricularia oryzae, Fusarium oxysporum, Aspergillus oryzae and A. fumigatus). Bacteria of the genus Bacillus (20%), Pseudomonas (33%) and Flavobacterium (40%) were predominant among the heterotrophic bacteria isolated from the marine sponges, soft coral and alga, respectively. Bioassay results revealed that 36 (63%) bacterial isolates displayed antifungal activity against at least one fungus, the alga (Sargassum sp.) being the source of highest number (80%) of producer strains. Twelve bacterial isolates inhibited all fungi. The MIC of the organic extracts of 12 bacteria ranged from 0.3 to 22.8 mg/L.