Plant Root Exudates Are Involved in Bacillus cereus AR156 Mediated Biocontrol Against Ralstonia solanacearum

Abstract

The biological control process mediated by microbes relies on multiple interactions among plants, pathogens and biocontrol agents (BCAs). One such efficient BCA is Bacillus cereus AR156, a bacterial strain that controls a broad spectrum of plant diseases and potentially works as a microbe elicitor of plant immune reactions. It remains unclear, however, whether the interaction between plants and B. cereus AR156 may facilitate composition changes of plant root exudates and whether these changes directly affect the growth of both plant pathogens and B. cereus AR156 itself. Here, we addressed these questions by analyzing the influences of root exudate changes mediated by B. cereus AR156 during biocontrol against tomato bacterial wilt caused by Ralstonia solanacearum. Indeed, some upregulated metabolites in tomato root exudates induced by B. cereus AR156 (REB), such as lactic acid and hexanoic acid, induced the growth and motile ability of in vitro B. cereus AR156 cells. Exogenously applying hexanoic acid and lactic acid to tomato plants showed positive biocontrol efficacy (46.6 and 39.36%) against tomato bacterial wilt, compared with 51.02% by B. cereus AR156 itself. Furthermore, fructose, lactic acid, sucrose and threonine at specific concentrations stimulated the biofilm formation of B. cereus AR156 in Luria-Bertan- Glycerol- Magnesium medium (LBGM), and we also detected more colonized cells of B. cereus AR156 on the tomato root surface after adding these four compounds to the system. These observations suggest that the ability of B. cereus AR156 to induce some specific components in plant root exudates was probably involved in further biocontrol processes.

Combination of beneficial bacteria improves blueberry production and soil quality

“…Specifically, Wang et al. (2019) reported that B. cereus AR156 can induce the secretion of organic acids, including lactic acid and caproic acid, from tomato roots, thereby promoting the growth and metabolism of root‐dwelling microorganisms. It suggested an important method that bacteria employ to improve their viability in barren soil, while consequently promoting soil organic matter.…”

“…Secretions of B. cereus AR156 are able to influence plant root secrets (Zhou et al., 2016). The change of root secrets has effects on plant growth; moreover, it provides more organic matter, such as lactic acid and caproic acid, for the soil (Wang et al., 2019). It has also been shown that PGPR are able to promote soil water retention (Zheng et al., 2018).…”

Isolation, Identification and Characterization of Rhizobacteria Strains for Biological Control of Bacterial Wilt (Ralstonia solanacearum) of Eggplant in China

“…This is probably due to too little fengycin being secreted by IMA 8 under the same conditions, although few studies display that iturin and fengycin produced by B. amyloliquefaciens have high activity against R. solanacearum [46,47], and purified fengycin has stronger antibacterial activity than iturin [47]. By comparison, no lipopeptides are found in strains IMA 4, IMA 7 and IMA 11 except IMA4 but they also show higher disease control efficacy, possibly being associated with mechanisms of induced resistance [33,48].…”

Biocontrol Potential of Sclerotinia sclerotiorum and Physiological Changes in Soybean in Response to Butia archeri Palm Rhizobacteria

“…In an endophytic strain of Enterobacter, Taghavi et al [73] observed the expression of genes related to the synthesis of antimicrobial compounds, such as 4-hydroxybenzoate and 2-phenylethanol, which may protect the plant from attack by both fungi and bacteria. In the specific case of Bacillus, a number of studies have indicated that this bacterium may facilitate alterations in the composition of the exudates of the roots, which may have a direct effect on the growth of pathogens [74]. However, extracellular polysaccharides, known as Microbe-Associated Molecular Patterns (MAMPs) [75], may be involved in the biocontrol processes of B. cereus.…”