Biocontrol of tomato wilt disease by Bacillus subtilis isolates from natural environments depends on conserved genes mediating biofilm formation

Abstract

Summary Bacillus subtilis and other Bacilli have long been used as biological control agents against plant bacterial diseases but the mechanisms by which the bacteria confer protection are not well understood. Our goal in this study was to isolate strains of B. subtilis that exhibit high levels of biocontrol efficacy from natural environments and to investigate the mechanisms by which these strains confer plant protection. We screened a total of sixty isolates collected from various locations across China and obtained six strains that exhibited above 50% biocontrol efficacy on tomato plants against the plant pathogen Ralstonia solanacearum under greenhouse conditions. These wild strains were able to form robust biofilms both in defined medium and on tomato plant roots and exhibited strong antagonistic activities against various plant pathogens in plate assays. We show that plant protection by those strains depended on widely conserved genes required for biofilm formation, including regulatory genes and genes for matrix production. We provide evidence suggesting that matrix production is critical for bacterial colonization on plant root surfaces. Finally, we have established a model system for studies of B. subtilis-tomato plant interactions in protection against a plant pathogen.

Identification and characterization of Bacillus subtilis from grass carp (Ctenopharynodon idellus) for use as probiotic additives in aquatic feed

“…Biofilm are microbial communities encased by a self-made extracellular matrix [52]. Formation of probiotic biofilm has many benefits to host intestinal health via: (1) producing specific secondary metabolites and significantly increasing the resistivity to biological, chemical and physical assaults in the gut [53], (2) increasing the colonization efficiency and local concentration of antibiotics, (3) protecting gut epithelium by competing with pathogens for adherence sites, and (4) inducing host immune reactions to the pathogens [54]. In this study, all the isolated B. subtilis strains were capable of forming biofilms at high levels.…”

Evolution of exploitative interactions during diversification in Bacillus subtilis biofilms

“…We still know relatively little about the natural diversity of biofilm formation within B. subtilis. Such information would be of great importance taking into account biocontrol properties of the species which rely on biofilm formation capability (Chen et al 2012b).…”

Complex Flocculation of Biofilm-forming Bacteria in the Presence of Flocculating Bacteria Isolated from Activated Sludge

“…The biofilm is a colony of microorganisms that forms on aquatic plants in marshlands or on stones in artificial ponds, where they can purify water. Furthermore, biofilms have applications in agriculture as microbial pesticides [12]. By forming biofilms on leaves or stems, some harmless bacteria can prevent attachment of and infection caused by phytopathogenic bacteria.…”