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KinD is a checkpoint protein linking spore formation to extracellular-matrix production in Bacillus subtilis biofilms.

Aguilar C, Vlamakis H, Guzman A, Losick R, Kolter R - MBio (2010)

Bottom Line: We have found that Spo0A~P levels are maintained at low levels in the matrix-deficient mutant, thereby delaying expression of sporulation-specific genes.Our data indicate that KinD displays a dual role as a phosphatase or a kinase and that its activity is linked to the presence of extracellular matrix in the biofilms.We propose a novel role for KinD in biofilms as a checkpoint protein that regulates the onset of sporulation by inhibiting the activity of Spo0A until matrix, or a component therein, is sensed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Bacillus subtilis cells form multicellular biofilm communities in which spatiotemporal regulation of gene expression occurs, leading to differentiation of multiple coexisting cell types. These cell types include matrix-producing and sporulating cells. Extracellular matrix production and sporulation are linked in that a mutant unable to produce matrix is delayed for sporulation. Here, we show that the delay in sporulation is not due to a growth advantage of the matrix-deficient mutant under these conditions. Instead, we show that the link between matrix production and sporulation is through the Spo0A signaling pathway. Both processes are regulated by the phosphorylated form of the master transcriptional regulator Spo0A. When cells have low levels of phosphorylated Spo0A (Spo0A~P), matrix genes are expressed; however, at higher levels of Spo0A~P, sporulation commences. We have found that Spo0A~P levels are maintained at low levels in the matrix-deficient mutant, thereby delaying expression of sporulation-specific genes. This is due to the activity of one of the components of the Spo0A phosphotransfer network, KinD. A deletion of kinD suppresses the sporulation defect of matrix mutants, while its overproduction delays sporulation. Our data indicate that KinD displays a dual role as a phosphatase or a kinase and that its activity is linked to the presence of extracellular matrix in the biofilms. We propose a novel role for KinD in biofilms as a checkpoint protein that regulates the onset of sporulation by inhibiting the activity of Spo0A until matrix, or a component therein, is sensed.

No MeSH data available.


The matrix mutant sporulation defect is medium dependent. Images are top views of cells grown under each condition. Spore counts of cells grown on solid 100% MSgg (black bars) or 10% MSgg (open bars) at 30°C for 72 h. Error bars indicate standard errors of the means.
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Figure 2: The matrix mutant sporulation defect is medium dependent. Images are top views of cells grown under each condition. Spore counts of cells grown on solid 100% MSgg (black bars) or 10% MSgg (open bars) at 30°C for 72 h. Error bars indicate standard errors of the means.

Mentions: When wild-type cells were grown on agar plates containing 10% MSgg medium, extracellular matrix was not produced, as evidenced by the lack of wrinkled architecture in wild-type colonies (Fig. 2, upper panels). Under these low-nutrient-level conditions, the matrix mutant sporulated to levels similar to those observed for the wild type (Fig. 2). Furthermore, the matrix mutant did not have a growth defect compared to what was observed for the wild type under low-nutrient-level conditions; both strains grew at rates similar to those observed for the matrix mutant in 100% MSgg medium (data not shown). These findings suggest that under biofilm-forming conditions, extracellular matrix allows cells to grow to a higher density and triggers the initiation of sporulation. In the absence of matrix, sporulation is delayed. However, under low-nutrient-level conditions, which trigger sporulation regardless of the presence of matrix, the sporulation delay is not observed. It is worth noting that while the sporulation levels were similar, the colony morphology of the matrix mutant on 10% MSgg was not identical to that observed for the wild type. For reasons we do not understand, mutations in the eps genes resulted in flared colonies (Fig. 2). This was not observed in the tasA single mutant (data not shown).


KinD is a checkpoint protein linking spore formation to extracellular-matrix production in Bacillus subtilis biofilms.

Aguilar C, Vlamakis H, Guzman A, Losick R, Kolter R - MBio (2010)

The matrix mutant sporulation defect is medium dependent. Images are top views of cells grown under each condition. Spore counts of cells grown on solid 100% MSgg (black bars) or 10% MSgg (open bars) at 30°C for 72 h. Error bars indicate standard errors of the means.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2912670&req=5

Figure 2: The matrix mutant sporulation defect is medium dependent. Images are top views of cells grown under each condition. Spore counts of cells grown on solid 100% MSgg (black bars) or 10% MSgg (open bars) at 30°C for 72 h. Error bars indicate standard errors of the means.
Mentions: When wild-type cells were grown on agar plates containing 10% MSgg medium, extracellular matrix was not produced, as evidenced by the lack of wrinkled architecture in wild-type colonies (Fig. 2, upper panels). Under these low-nutrient-level conditions, the matrix mutant sporulated to levels similar to those observed for the wild type (Fig. 2). Furthermore, the matrix mutant did not have a growth defect compared to what was observed for the wild type under low-nutrient-level conditions; both strains grew at rates similar to those observed for the matrix mutant in 100% MSgg medium (data not shown). These findings suggest that under biofilm-forming conditions, extracellular matrix allows cells to grow to a higher density and triggers the initiation of sporulation. In the absence of matrix, sporulation is delayed. However, under low-nutrient-level conditions, which trigger sporulation regardless of the presence of matrix, the sporulation delay is not observed. It is worth noting that while the sporulation levels were similar, the colony morphology of the matrix mutant on 10% MSgg was not identical to that observed for the wild type. For reasons we do not understand, mutations in the eps genes resulted in flared colonies (Fig. 2). This was not observed in the tasA single mutant (data not shown).

Bottom Line: We have found that Spo0A~P levels are maintained at low levels in the matrix-deficient mutant, thereby delaying expression of sporulation-specific genes.Our data indicate that KinD displays a dual role as a phosphatase or a kinase and that its activity is linked to the presence of extracellular matrix in the biofilms.We propose a novel role for KinD in biofilms as a checkpoint protein that regulates the onset of sporulation by inhibiting the activity of Spo0A until matrix, or a component therein, is sensed.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Bacillus subtilis cells form multicellular biofilm communities in which spatiotemporal regulation of gene expression occurs, leading to differentiation of multiple coexisting cell types. These cell types include matrix-producing and sporulating cells. Extracellular matrix production and sporulation are linked in that a mutant unable to produce matrix is delayed for sporulation. Here, we show that the delay in sporulation is not due to a growth advantage of the matrix-deficient mutant under these conditions. Instead, we show that the link between matrix production and sporulation is through the Spo0A signaling pathway. Both processes are regulated by the phosphorylated form of the master transcriptional regulator Spo0A. When cells have low levels of phosphorylated Spo0A (Spo0A~P), matrix genes are expressed; however, at higher levels of Spo0A~P, sporulation commences. We have found that Spo0A~P levels are maintained at low levels in the matrix-deficient mutant, thereby delaying expression of sporulation-specific genes. This is due to the activity of one of the components of the Spo0A phosphotransfer network, KinD. A deletion of kinD suppresses the sporulation defect of matrix mutants, while its overproduction delays sporulation. Our data indicate that KinD displays a dual role as a phosphatase or a kinase and that its activity is linked to the presence of extracellular matrix in the biofilms. We propose a novel role for KinD in biofilms as a checkpoint protein that regulates the onset of sporulation by inhibiting the activity of Spo0A until matrix, or a component therein, is sensed.

No MeSH data available.