Specific Bacillus subtilis 168 variants form biofilms on nutrient-rich medium

Abstract

Bacillus subtilis is an intensively studied Gram-positive bacterium that has become one of the models for biofilm development. B. subtilis 168 is a well-known domesticated strain that has been suggested to be deficient in robust biofilm formation. Moreover, the diversity of available B. subtilis laboratory strains and their derivatives have made it difficult to compare independent studies related to biofilm formation. Here, we analysed numerous 168 stocks from multiple laboratories for their ability to develop biofilms in different set-ups and media. We report a wide variation among the biofilm-forming capabilities of diverse stocks of B. subtilis 168, both in architecturally complex colonies and liquid-air interface pellicles, as well as during plant root colonization. Some 168 variants are indeed unable to develop robust biofilm structures, while others do so as efficiently as the non-domesticated NCIB 3610 strain. In all cases studied, the addition of glucose to the medium dramatically improved biofilm development of the laboratory strains. Furthermore, the expression of biofilm matrix component operons, epsA-O and tapA-sipW-tasA, was monitored during colony biofilm formation. We found a lack of direct correlation between the expression of these genes and the complexity of wrinkles in colony biofilms. However, the presence of a single mutation in the exopolysaccharide-related gene epsC correlates with the ability of the stocks tested to form architecturally complex colonies and pellicles, and to colonize plant roots.

Evolution of exploitative interactions during diversification in Bacillus subtilis biofilms

“…Variations in biofilm formation within laboratory B. subtilis strains are commonly associated with the domestication problem, that occurs during cultivation of a bacterium in rich LB medium (McLoon et al 2011;Leiman et al 2014;Gallegos-Monterrosa, Mhatre and Kovács 2016). Indeed, biofilm-altered variants of B. subtilis could be experimentally evolved in static and liquid LB, mostly carrying mutations in the biofilm regulator sinR (Leiman et al 2014).…”

Evolution of exploitative interactions during diversification inBacillus subtilisbiofilms

“…Variations in biofilm formation within laboratory B. subtilis strains are commonly associated with the domestication problem, that occurs during cultivation of a bacterium in rich LB medium (McLoon et al 2011;Leiman et al 2014;Gallegos-Monterrosa, Mhatre and Kovács 2016).…”

Hampered motility promotes the evolution of wrinkly phenotype in Bacillus subtilis

“…Various biofilm types are established by Bacillus subtilis under laboratory conditions, including pellicles at the air-medium interface (Branda et al, 2001;Gallegos-Monterrosa et al, 2016;Mhatre et al, 2016). B. subtilis cells inhabiting the biofilms are sessile and produce a matrix consisting of exopolysaccharides (EPS), protein fibers (TasA) and hydrophobin protein (BslA) (Branda et al, 2004;Romero et al, 2010;Kobayashi and Iwano, 2012;Hobley et al, 2013).…”