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.