| Plant-associated bacteria have a good application prospect as biocontrol agents. The protective and growth-promoting effect of biocontrol bacteria depend on a variety of mechanisms including producting antibiotics for inhibiting the affection of pathogens to the host plant tissues. Many genes are involved in the synthesis of antibiotics in species of Bacillus, including the genes or operons encoding antibiotics and the important regulatory factors which were essential for the globle regulation involved in the coordination of variety of cell processes.The results were as follows:At first, ten antibiotic activity related genes were amplified from the genomic DNA of Bacillus amyloliquefaciens PEBA20. The alignments of these genes showed66%-99%identies with similar genes of other Bacillus species in GenBank, and showed a highest identies with B. amyloliquefaciens as well as large differences with other Bacillus. These genes are widespread in Bacillus. Most Bacillus species have more than one kind of antibiotic related genes. These coding and regulator genes of antibiotics that exist in B. amyloliquefaciens PEBA20may have a direct correlation with the biocontrol activity of PEBA20.Secondly, the spoOA gene was cloned. The sequenced result showed that the length of the intact open reading frame of spoOA gene is801base pairs, encoding266amino acids. Both base sequence and amino acid sequence of spoOA share high identities to its homologues present in different Bacillus species, and share the highest identies with B. amyloliquefaciens.Then, we designed a suicide vector-based gene knockout method to construct mutant, and primarily constructed a mutant of regulator gene spoOA. We have obtained a mutant recombinant plasmid of spoOAF-spoOAR and its sequence was analysed. In addition, the construction of suicide recombinant plasmid spo0AF-spo0AR-pWM91, subsequent transformation to PEBA20, and mutant screening are underway. |
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