Soil Bacteria as a Natural Source of Antifungal Agents against Phytopathogenic Fungus: Aspergillus niger
Soil bacteria are able to synthesize a wide range of metabolites with fungicidal activity. Nine bacterial isolates were obtained from the botanical garden of University of Calabar. Preliminary examination of isolates was carried out using morphological characteristics and biochemical analysis. These isolates were designated with codes SB1, SB2, SB3, SB4, SB5, SB6, SB7, and SB8. Bacterial isolates were evaluated for their potentials of antagonism against Aspergillus niger isolated from spoiled vegetables like tomatoes by using agar diffusion technique. Percentage inhibition of mycelial growth by these isolates recorded values as 27%, 0%, 66%, 40%, 97%, 0% and 23% respectively. Isolates were analyzed through several biochemical tests and were identified as Bacillus sp., Enterobacter spp., Pseudomonas spp., Proteus spp., Escherichia coli, Streptococcus spp. and Staphylococcus spp.respectively. These result indicated that bacterial species exhibited varying degree of antagonism against the fungus Aspergillus niger. Escherichia coli showed maximum inhibitory potential against tested fungus with reduction of up to 97% in their mycelial fungal growth, followed by Pseudomonas spp. and Bacillus spp. with 66.7% reduction. From the results obtained, it is found that the bacterial species isolated from the soil samples are effective as antifungal agents against phyto-pathogenic fungi. Escherichia coli, Pseudomonas spp., Bacillus spp. had more antagonistic effect on vegetative growth of tested fungi (Aspergillus niger). These bacterial species showed higher levels of inhibitory effect on fungal spore germination. The presented data exhibit the antifungal activity of bacterial species and indicate the possibility of using these bacterial species as a biological agent to control the phyto pathogenic fungi.
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