Biofilm-Defective Mutants of <i>Bacillus subtilis</i>

Abstract

Many bacteria can adopt organized, sessile, communal lifestyles. The gram-positive bacterium, Bacillus subtilis,forms biofilms on solid surfaces and at air-liquid interfaces, and biofilm development is dependent on environmental conditions. We demonstrate that biofilm formation by B. subtilis strain JH642 can be either activated or repressed by glucose, depending on the growth medium used, and that these glucose effects are at least in part mediated by the catabolite control protein, CcpA. Starting with a chromosomal Tn917-LTV3 insertional library, we isolated mutants that are defective for biofilm formation. The biofilm defects of these mutants were observable in both rich and minimal media, and both on polyvinylchloride abiotic surfaces and in borosilicate tubes. Two mutants were defective in flagellar synthesis. Chemotaxis was shown to be less important for biofilm formation than was flagellar-driven motility. Although motility is known to be required for biofilm formation in other bacteria, this had not previously been demonstrated for B. subtilis. In addition, our study suggests roles for glutamate synthase, GltAB, and an aminopeptidase, AmpS. The loss of these enzymes did not decrease growth or cellular motility but had dramatic effects on biofilm formation under all conditions assayed. The effect of the gltAB defect on biofilm formation could not be due to a decrease in poly-γ-glutamate synthesis since this polymer proved to be nonessential for robust biofilm formation. High exogenous concentrations of glutamate, aspartate, glutamine or proline did not override the glutamate synthase requirement. This is the first report showing that glutamate synthase and a cytoplasmic aminopeptidase play roles in bacterial biofilm formation. Possible mechanistic implications and potential roles of biofilm formation in other developmental processes are discussed.

Influence of the σBStress Factor andyxaB, the Gene for a Putative Exopolysaccharide Synthase under σBControl, on Biofilm Formation

“…For example, in B. subtilis, in addition to the epsA to -O and yqxM-sipW-tasA genes required for matrix formation (5), a number of genes such as ampS, gltAB, yoaW, and pgcA, which seemingly fulfill other crucial, often unknown, functions, somehow participate in biofilm development (7,16,25). We observed that transcription starting at p yxaAB is unchanged during biofilm formation, suggesting that the gene is not required for this process.…”

Effect of Periodontal Pathogens on the Metatranscriptome of a Healthy Multispecies Biofilm Model

“…This enzyme has been shown to play a key role in biofilm formation in Mycobacterium bovis (13). Moreover, the loss of this enzyme in Bacillus subtilis did not decrease growth or cellular motility but had dramatic effects on biofilm formation (12). Finally, the gene set PTS, which is related to the use of different sugars, was also upregulated during biofilm formation in the pathogenic biofilm.…”

“…The gene sets defined as photosynthesis or photosynthesis proteins also comprised genes involved in the respiratory chain and vitamin metabolism. In fact, the upregulated genes were the different subunits (a, b, c) of the ATP synthase complex and the cobaltochelatase gene (cobN), which is involved in the biosynthesis of coenzyme B 12 .…”

Bacillus subtilisPellicle Formation Proceeds through Genetically Defined Morphological Changes

“…Thus, the SinI/R system has been proposed as a master regulatory system that governs the transition from a planktonic state to a biofilm state (11,33). Moreover, many genes involved in biofilm formation have also been identified via genome-wide screening, using transposon insertions and the Bacillus subtilis functional analysis collection of mutants, but the precise roles of these genes in biofilm formation are still unknown (5,10).…”