Contribution of Bacillomycin D in Bacillus amyloliquefaciens SQR9 to Antifungal Activity and Biofilm Formation

Abstract

cBacillus amyloliquefaciens strains are capable of suppressing soilborne pathogens through the secretion of an array of lipopeptides and root colonization, and biofilm formation ability is considered a prerequisite for efficient root colonization. In this study, we report that one of the lipopeptide compounds (bacillomycin D) produced by the rhizosphere strain Bacillus amyloliquefaciens SQR9 not only plays a vital role in the antagonistic activity against Fusarium oxysporum but also affects the expression of the genes involved in biofilm formation. When the bacillomycin D and fengycin synthesis pathways were individually disrupted, mutant SQR9M1, which was deficient in the production of bacillomycin D, only showed minor antagonistic activity against F. oxysporum, but another mutant, SQR9M2, which was deficient in production of fengycin, showed antagonistic activity equivalent to that of the wild-type strain of B. amyloliquefaciens SQR9. The results from in vitro, root in situ, and quantitative reverse transcription-PCR studies demonstrated that bacillomycin D contributes to the establishment of biofilms. Interestingly, the addition of bacillomycin D could significantly increase the expression levels of kinC gene, but KinC activation is not triggered by leaking of potassium. These findings suggest that bacillomycin D contributes not only to biocontrol activity but also to biofilm formation in strain B. amyloliquefaciens SQR9.

Host and tissue preferences of Enterobacter cloacae and Bacillus amyloliquefaciens for endophytic colonization

“…The sharper decreases in 344 countings when sterile and non-sterile conditions were compared suggest this isolate has a lower competitive ability than 629. Indeed, several studies show that species of Bacillus produce more antimicrobial compounds than species of Enterobacter (Xu et al, 2013). Our previous greenhouse studies with these two bacteria in cacao seedlings have also shown higher growthpromotion and stress-reduction effects for 629 than for 344 (Leite et al, 2013).…”

Antifungal Effects of Lipopeptide Produced by <i>Bacillus amyloliquefaciens</i> BH072

“…In this study, the AKP activity, conductivity and protein contents were measured; and results suggested that iturin A undermined the integrity of the fungal cell wall and membrane, causing leakage of the contents. Antibiotics in the iturin family were found to act upon sterols presenting in the cytoplasmic membrane of microorganisms [38]. Although cell membrane was the most significant defense and prime sites for antimicrobial attack, destroy of fungal cell wall was also seriously targeted for antifungal activity.…”

Improvement of Antagonistic Activity of Bacillus megaterium MHT6 against Fusarium moniliforme using He-Ne Laser Irradiation

“…Meanwhile, we can see the peak of FPII in MHT88 is higher than that in MHT6. The fractions obtained from the MHT6 and MHT88 were separately tested for their inhibitory activity by oxford cup method (Xu et al, 2013). The results given in Table 4 showed that fraction FP-II showed significant inhibitory activity against the growth of F. moniliforme L8.…”

“…The antagonistic ability of MHT6 fermentation broth against F. moniliforme L8 was tested by culture filtrate test using oxford cup method (Yoshida et al, 2001;Xu et al, 2013). The MHT6 was inoculated in 250mL nutrient broth at 37°C for 72 h. After centrifuging the culture at 10,000 g for 10 min, supernatant was collected and filtered through a 0.22 μm cellulose nitrate filters under sterile conditions.…”

“…Each colony was performed in triplicate. Data analysis was performed by ANOVA using SPASS19.0 software (SPSS, Inc., USA) at P=0.05 Antagonistic activity of mutants' fermentation broth against F. moniliforme L8: Antifungal activities of cell-free supernatants in eight selected mutants (M36, M56, M88, M68, M78, M80, M86, M67) were tested by culture filtrate test using oxford cup method (Yoshida et al, 2001;Xu et al, 2013). The diameter of inhibition zone was measured.…”