Characterization of Bacillus amyloliquefaciens DA12 Showing Potent Antifungal Activity against Mycotoxigenic Fusarium Species

Abstract

In an attempt to develop a biological control agent against mycotoxigenic Fusarium species, we isolated Bacillus amyloliquefaciens strain DA12 from soil and explored its antimicrobial activities. DA12 was active against the growth of mycotoxigenic F. asiaticum, F. graminearum, F. proliferatum, and F. verticillioides both in vitro and in planta (maize). Further screening using dual culture extended the activity range of strain DA12 against other fungal pathogens including Botrytis cinerea, Colletotrichum coccodes, Endothia parasitica, Fusarium oxysporum, Raffaelea quercus-mongolicae, and Rhizoctonia solani. The butanol extract of the culture filtrate of B. amyloliquefaciens DA12 highly inhibited the germination of F. graminearum macroconidia with inhibition rate 83% at a concentration of 31.3 μg/ml and 100% at a concentration of 250 μg/ml. The antifungal metabolite from the butanol extract was identified as iturin A by thin layer chromatography-bioautography. In addition, volatile organic compounds produced by DA12 were able to inhibit mycelial growth of various phytopathogenic fungi. The volatile compounds were identified as 2-heptanone, 5-methyl heptanone and 6-methyl heptanone by gas chromatography-mass spectrometry (GC-MS) analysis. These results indicate that the antagonistic activity of Bacillus amyloliquefaciens DA12 was attributable to iturin A and volatile heptanones, and the strain could be used as a biocontrol agent to reduce the development of Fusarium diseases and mycotoxin contamination of crops.

In vitro study of biocontrol potential of rhizospheric Pseudomonas aeruginosa against Fusarium oxysporum f. sp. cucumerinum

“…In vitro dual culture test is one of the key tests used for preliminary screening of biological control agents. Antagonistic effects are usually confirmed by the formation of inhibition zones between the bacteria isolates and the fungal isolates (Ji et al 2014) or by measuring the percent of radial mycelial growth inhibition towards the bacterial isolates (Lee et al 2017).…”

“…Raza et al (2016) demonstrated the role of VOCs produced by P. fluorescens WR-1 in biocontrol activities. Kandel et al (2017) and Lee et al (2017) also reported VOCs mediated antifungal activities recently.…”

“…A number of soil bacterial strains have been exploited for their plant growth promotion and biocontrol potentials, particularly the genera Bacillus (Lee et al 2017), Pseudomonas (Priyanka et al 2017), and Streptomyces (Lu et al 2016). The genus Pseudomonas possesses superior biocontrol properties because of their adaptive metabolism and their ability to produce a range of antifungal compounds (Trivedi et al 2008).…”

Establishment of a rapeseed meal fermentation model for iturin A production by Bacillus amyloliquefaciens CX‐20

“…It consists of a cyclic heptapeptide linked to a 14 to 17-carbon bamino fatty acid chain (Ongena and Jacques, 2008). Its special molecular structure that enables it to change the permeability and integrity of the cell membrane makes it the principal antifungal substance responsible for the biological control activity of Bacillus species against a broad spectrum of fungal pathogens, such as Aspergillus (Cho et al, 2009), Fusarium (Lee et al, 2017), Verticillium (Han et al, 2015), Alternaria (Arrebola et al, 2010), Colletotrichum (Kim et al, 2010), Phytophthora (Park et al, 2016) and Phoma (Kalai-Grami et al, 2016). Moreover, due to its low toxicity, low allergenicity, biodegradability, high stability and environmental friendliness (Meena and Kanwar, 2015), iturin A is an ideal potential biological control agent to reduce the use of chemical pesticides in agriculture.…”

Antifungal activity of volatile compounds produced by endophytic Bacillus subtilis DZSY21 against Curvularia lunata

“…Error bars represent the standard deviation. The assay was repeated three times exhibited great antagonistic activities toward various fungal pathogens by producing iturin A and heptanone (Lee et al 2017). IA, naturally produced by banana, exhibited strong activity against Escherichia coli by damaging cell membranes and altering protein expression (Ando et al 2015).…”