Enhancement of Biocontrol Activities and Cyclic Lipopeptides Production by Chemical Mutagenesis of Bacillus subtilis XF-1, a Biocontrol Agent of Plasmodiophora brassicae and Fusarium solani

Abstract

Bacillus subtilis XF-1 has been used as a biocontrol agent of clubroot disease of crucifers infected by Plasmodiophora brassicae, an obligate pathogen. In order to maximize the growth inhibition of the pathogen, random mutagenesis using N-methyl-N'-nitro-N-nitrosoguanidine was applied to strain XF-1. The efficacy of 226 selected mutants was assessed against the growth of an indicator fungal pathogen: Fusarium solani using agar plate assay and the disruptive effects on the resting spores of P. brassicae. Four mutants exhibited inhibition activity significantly higher than the wild type. The cell extracts of these mutants and the XF-1 were subjected to matrix-assisted laser desorption ionization-time of flight mass spectra analysis, and three families of cyclic lipopeptides (CLPs) fengycin, surfactin and iturin were identified from the parental strain and the screened mutants. However, the relative contents and compound diversity changed after mutagenesis, and there was slight variation in the surfactin and fengycin. Notably, only 5 iturin components were discovered from the wild strain XF-1, but 13 were obtained from the mutant strains, and the relative CLPs contents of all mutant strains increased substantially. The results suggested that CLPs might be one of main biocontrol mechanisms of the clubroot disease by XF-1. The 4 mutants are far more effective than the parental strain, and they would be promising biocontrol candidates not only against P. brassicae but probably other plant diseases caused by fungi.

Potential biocontrol and superlative plant growth promoting activity of indigenous Bacillus mojavensis PB-35(R11) of soybean (Glycine max) rhizosphere

“…In the present study, among 95 soybean rhizosphere isolates, PB-35(R11) showed the greatest potential, with a a broad spectrum of in vitro antagonistic activity towards the fungal pathogen as well as PGP traits. Many Bacillus isolates have been shown to exhibit activity against phytopathogenic fungi, making them good biocontrol candidates [32,38,44]. In the present study, strain B. mojavensis PB-35(R11) exhibited strong antifungal activity (40 mm zone of inhibition) against the fungal pathogen R. solani, which can mainly be attributed to its production of phosphate, ammonia, hydrogen cyanide, nitrogen-fixing activity, chitinase, IAA, and siderophore.…”

<i>Bacillus subtilis Strains</i> with Antifungal Activity against the Phytopathogenic Fungi

“…The antagonistic activity of Bacillus is associated with the synthesis of various antimicrobial peptides [8] [9], secreted enzymes [10], proteins [11] and volatile organic compounds (VOCs) [5] [10]. Many Bacillus isolates were shown to have antifungal activity against phytopathogenic fungi that make them good biocontrol candidates [12] [13] [14]. Cyclic lipopeptide fengycin plays an important role in this process [15].…”

Improvement of iturin A production inBacillus subtilisZK0 by overexpression of thecomAandsigAgenes

“…The molecular weights of these peaks were consistent with iturin A derivatives containing β ‐amino fatty‐acid chains of C11–C13 (Li et al . ). The results from RP‐HPLC and LC‐MS strongly indicated that overexpression of comA and sigA improved iturin A production by B. subtilis ZK0.…”