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Medium Effect on Antagonistic Activity and Detection of Nonribosomal Peptide Synthetase Genes in Epiphytic Bacillus Strains
Author(s)
Apimeteethamrong, Suchitra
Date Issued
January 1, 2021
Type
Article
Abstract
The biosynthesis of non-ribosomal peptides (NRPs) in biocontrol bacteria was one of the major antagonistic mechanisms for their application in agriculture. Bacillus spp. 1021, 2211 and 3210 were previously shown to inhibit mycelial growth of the leaf blast fungus Pyricularia oryzae. Here, we aimed to further study the antagonistic mechanism in those three strains. Cell-free supernatants obtained from bacteria grown in potato dextrose broth (PDB) exhibited a higher degree of inhibition against P. oryzae when compared to those obtained from nutrient broth (NB). This indicated the effect of culture media in the production of extracellular antibiotic compounds by these strains. Phylogenetic analysis of their partial 16S rRNA gene sequences indicated a close relationship between the three strains and Bacillus siamensis KCTC13613T, Bacillus amyloliquefaciens DSM7T and Bacillus velezensis CR-502T. Complete genome sequences of these Bacillus species were analyzed on the antiSMASH server to identify the presence of NRP biosynthesis gene clusters. Non-degenerate primers were designed for the detection of the core biosynthesis genes for surfactin (srfAA), fengycin (fenC) and bacillibactin (dhbF). All three genes were amplified in strains 1021 and 2211, while only srfAA and dhbF were detected in strain 3210. Phylogenetic analysis of the deduced amino acid sequences indicated that the sequences of strain 1021 were distinct from those of strains 2211 and 3210. This result indirectly suggests the possibility of NRP production as the antagonistic mechanism of these three strains.
Citation
Current Applied Science and Technology, 21(4), 637-651, 2021