Abstract
Strain EGB3 was isolated from the gut of earthworm fed with sterile soil and identified as Pseudomonas stutzeri on the basis of biochemical tests and by comparison of 16S rDNA sequences. This bacterium exhibits a broad-spectrum antifungal activity towards soil borne phytopathogenic fungi (Fusarium oxysporum, Fusarium solani, Fusarium moniliformae, Fusarium udum, Macrophomena phaseolina, Rhizoctonia solani, Colletotrichum capsicii, Aspergillus flavus, and Aspergillus niger). The antifungal metabolite produced by EGB3 was extracted and characterized to determine the nature of the active molecules (volatile and non-volatile). The bioactive compound was thermostable upto 80°C for 10 min. The zone of inhibition was observed after 6 h of incubation and increased up to 36 h and there was no change in zone of inhibition after 36 h of incubation. EGB3 was an antagonist against a range of phytopathogenic fungi that infect groundnut plants. Key words: phytopathogenic fungi, EGB3, Pseudomonas stutzeri, antifungal metabolites.
Highlights
Microorganisms in nature compete for survival in their habitats
Each plate consisted of three wells, of which one well was filled with earthworm gut bacteria (EGB), standard antibiotic solution and control, respectively The plates were incubated at 28°C for 72 h
To determine whether the antifungal metabolites or the siderophores responsible for the antagonistic property, the earthworm gut bacteria 3 (EGB3) triplicates was grown on potato dextrose agar plates supplemented with 1% ferric chloride and tested for antagonistic activity by agar well diffusion method
Summary
Microorganisms in nature compete for survival in their habitats. This biological task of antagonistic nature is achieved by the development of competitive mechanisms such as the production of antimicrobial agents like antibiotics, siderophores, toxins and enzymes, etc.Antagonistic microorganisms, by their interaction with various pathogens, play a major role in microbial equilibrium and serve as powerful agents for biological disease control. Fusarium udum, Macrophomena phaseolina, Rhizoctonia solani, Colletotrichum capsicii, Aspergillus flavus, and Aspergillus niger) were used to determine the antifungal activity of the earthworm gut bacteria (EGB). Antifungal activity of EGB3 against the test fungi was assayed using the agar well diffusion method.
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