Antibacterial Activity of Endophytic Bacteria Against Sugar Beet Root Rot Agent by Volatile Organic Compound Production and Induction of Systemic Resistance

Abstract

The volatile organic compounds (VOCs) produced by endophytic bacteria have a significant role in the control of phytopathogens. In this research, the VOCs produced by the endophytic bacteria Streptomyces sp. B86, Pantoea sp. Dez632, Pseudomonas sp. Bt851, and Stenotrophomonas sp. Sh622 isolated from healthy sugar beet (Beta vulgaris) and sea beet (Beta maritima) were evaluated for their effects on the virulence traits of Bacillus pumilus Isf19, the causal agent of harvested sugar beet root rot disease. The gas chromatographymass spectrometry (GC-MS) analysis revealed that B86, Dez632, Bt851, and Sh622 produced 15, 28, 30, and 20 VOCs, respectively, with high quality. All antagonistic endophytic bacteria produced VOCs that significantly reduced soft root symptoms and inhibited the growth of B. pumilus Isf19 at different levels. The VOCs produced by endophytic bacteria significantly reduced swarming, swimming, and twitching motility by B. pumilus Isf19, which are important to pathogenicity. Our results revealed that VOCs produced by Sh622 and Bt851 significantly reduced attachment of B. pumilus Isf19 cells to sugar beetroots, and also all endophytic bacteria tested significantly reduced chemotaxis motility of the pathogen toward root extract. The VOCs produced by Dez632 and Bt851 significantly upregulated the expression levels of defense genes related to soft rot resistance. Induction of PR1 and NBS-LRR2 genes in sugar beetroot slices suggests the involvement of SA and JA pathways, respectively, in the induction of resistance against pathogen attack. Based on our results, the antibacterial VOCs produced by endophytic bacteria investigated in this study can reduce soft rot incidence.

Breynia cernua: Chemical Profiling of Volatile Compounds in the Stem Extract and Its Antioxidant, Antibacterial, Antiplasmodial and Anticancer Activity In Vitro and In Silico

“…Decane, 2,4-dimethyl- was identified in the endophytic bacterium Pantoea sp. strain Dez632 and possessed antibacterial activity [ 38 ]. Octane, 3,4,5,6-tetramethyl-, contained in the endophytic bacterium Pseudomonas sp.…”

“…Octane, 3,4,5,6-tetramethyl-, contained in the endophytic bacterium Pseudomonas sp. strain Bt851, exhibited antibacterial activity [ 38 ]. Oxalic acid, cyclohexyl nonyl ester, isolated from the methanol extract of Rheum ribes , showed an inhibitory effect on Escherichia coli [ 39 ].…”

Characterizing bacterial pathogen causing sugar beet dry rot of root at harvest and its suppression by endophytic bacteria

“…Recently, our previous research showed the potential activity of several endophytic bacteria, isolated from sugar beet and sea beet plants to reduce soft rot of post-harvested sugar beet roots 32 . In this study, the above endophytic bacteria were evaluated for their potential to inhibit in vitro growth and their in uence on virulence traits of dry rot agent.…”

“…Antibacterial activity of VOCs produced by endophytic bacteria. The antibacterial activity of VOCs against bacterial pathogen was assessed on NA medium using a dual-culture technique 32 . The 24 h growth of the endophytic bacteria (adjusted to the concentration of about 1× 10 11 CFU/ml) was streaked on one side of the plate, while the opposite side was spot inoculated with 5 µl of the bacterial pathogen (1× 10 8 CFU/ml).…”

“…The adsorbed VOCs were then extracted by shaking for 15 min, followed by centrifugation (5000 rpm, 15 min). The obtained supernatants were analyzed by a gas chromatography device connected to a mass spectrometer (Agilent 7890B GC System / 5977A MSD, Agilent Technologies, USA) 32 .…”