Evaluation of Antagonistic Potential of Soil Bacteria against Plant Pathogenic 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 Gram’s reaction. These isolates were designated with codes SB1, SB2, SB3, SB4, SB5, SB6, SB7, and SB8. Bacterial isolates were evaluated for their potential 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 fungal growth. Pseudomonas spp. and Bacillus spp. followed with 66.7%. This result showed that Pseudomonas spp. and Bacillus spp. exhibited similar percentage of antagonism against Aspergillus niger. From the results obtained, it can be interpreted that test bacterial species can be used as fungal agents like Aspergillus niger.