Isolation and characterization of a potential biocontrol agent Bacillus KM5 from rhizosphere soil of a rice plant.

摘要

Twelve microbial isolates were isolated and purified from rhizosphere soil of a healthy rice plant. One of the isolate named as KM 5 showed antagonist activity in vitro against Sclerotium rolfsii Saccardo, Helminthosporium oryzae, Gibberella fujikuroi, Rhizoctonia solani Nees and Fusarium udum. KM 5 was characterized by microscopic, Gram stain and biochemical methods belonging to genus Bacillus. The genus Bacillus was further confirmed by isolation of genomic DNA, 16S rRNA amplification using Bacillus specific primers. Sequencing of the PCR amplified product using 775 base pairs and further NJ phylogenetic analysis confirmed that the microorganism is a new strain of bacterium named as Bacillus sp. KM 5. Partial sequence of 16S rRNA gene has been deposited to NCBI GenBank data base with accession no. EU266068 and deposited to MTCC with accession no. MTCC-5413. The cell free culture filtrate of Bacillus sp. KM 5 inhibited the growth of all test fungi. An antifungal protein produced by Bacillus sp. KM 5 was purified by ammonium sulphate. The protein was stable at 20, 40, 60 and 100 degrees C and remained active after sterilization at 121 degrees C for 15 min.