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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