The sporulation transcription factor Spo0A is required for biofilm development in Bacillus subtilis

Abstract

Biofilms are structured communities of cells encased in a polymeric matrix and adherent to a surface, interface or each other. We report here that the soil bacterium Bacillus subtilis forms biofilms. By confocal scanning laser microscopy, we observed that B. subtilis adhered to abiotic surfaces and formed a three‐dimensional structure ≥ 30 µm in depth. These biofilms appeared to be at least partly encased in an extracellular polysaccharide matrix, as they could be stained with Calcofluor, a polysaccharide‐binding dye. To understand the molecular mechanism of biofilm formation, we screened previously characterized mutants for a defect in biofilm formation. We found that mutations in spo0A, which encodes the major early sporulation transcription factor, caused a defect in biofilm formation. spo0A mutant cells adhered to a surface in a monolayer of cells rather than a three‐dimensional biofilm. The requirement of Spo0A for biofilm development appears to result from its role in negatively regulating AbrB. Mutations in abrB suppressed the biofilm defect of a spo0A mutant, indicating that AbrB negatively regulates at least one gene that is required for the transition from a monolayer of attached cells to a mature biofilm. Implications of biofilm development for the ecology of B. subtilis are discussed.

kinA mRNA is missing a stop codon in the undomesticated Bacillus subtilis strain ATCC 6051

“…However, when these strains harboured kinA 168 they formed spores on pellicles efficiently, even in a kinC or kinD mutant background ( Fig. 2b) As expected, based on a previous report (Hamon & Lazazzera, 2001), the abrB mutation bypassed the requirement for KinC and KinD in pellicle formation (Fig. 2a, W1045).…”

“…In the laboratory strain 168, pellicle formation is negatively controlled by AbrB, expression of which is repressed by a low level of Spo0A~P (Fujita et al, 2005;Hamon & Lazazzera, 2001). As has been shown for the laboratory strain (Hamon & Lazazzera, 2001), in strain 6051 pellicle formation appears to be controlled by other kinases, KinC and KinD, as kinC and kinD mutant strains form extremely thin pellicles (Fig.…”

“…KinA and KinB are major kinases for sporulation, since a kinA kinB double-mutant strain cannot make spores (Trach & Hoch, 1993). On the other hand, mutations in kinC, kinD or kinE reduce biofilm formation but not sporulation, whereas mutations in kinA or kinB do not affect biofilm formation (Hamon & Lazazzera, 2001;Jiang et al, 1999;Kobayashi et al, 1995;. The function of Spo0A in biofilm formation is to repress abrB transcription, since abrB inactivation can restore biofilm formation in a spo0A mutant strain (Hamon & Lazazzera, 2001).…”

“…On the other hand, mutations in kinC, kinD or kinE reduce biofilm formation but not sporulation, whereas mutations in kinA or kinB do not affect biofilm formation (Hamon & Lazazzera, 2001;Jiang et al, 1999;Kobayashi et al, 1995;. The function of Spo0A in biofilm formation is to repress abrB transcription, since abrB inactivation can restore biofilm formation in a spo0A mutant strain (Hamon & Lazazzera, 2001). In addition, although the kinA kinB double mutation does not affect abrB transcription, in a kinA kinB kinC kinD quadruple-mutant strain, the level of abrB transcription is elevated (Jiang et al, 2000).…”

Phosphorylation of Spo0A by the Histidine Kinase KinD Requires the Lipoprotein Med in Bacillus subtilis

“…Several of these responses, such as spore formation, cannibalism, and biofilm formation, require the same master regulatory protein, Spo0A (11,13,15,18,35,36). Spo0A is a member of the response regulator family of transcription factors and is active in its phosphorylated state (Spo0AϳP) (14,22).…”