Mucin can enhance growth, biofilm formation, and survival of Streptococcus mutans.

Streptococcus mutans is a member of the dental plaque and is the primary causative agent of dental caries. It can survive extended periods of starvation, which may occur in different niches within the oral cavity. We have found that mucin compensated for the absence of amino acids to promote exponential growth and biofilm formation of S.

Coupling of σG activation to completion of engulfment during sporulation of Bacillus subtilis survives large perturbations to DNA translocation and replication.

Spore formation in Bacillus subtilis is characterized by activation of RNA polymerase sigma factors, including the late-expressed σ(G). During spore formation an asymmetric division occurs, yielding the smaller prespore and the larger mother cell. At division, only 30% of the chromosome is in the prespore, and the rest is then translocated into the prespore.

Regulation of growth of the mother cell and chromosome replication during sporulation of Bacillus subtilis.

During spore formation, Bacillus subtilis divides asymmetrically, resulting in two cells with different fates. Immediately after division, the transcription factor σ(F) becomes active in the smaller prespore, followed by activation of σ(E) in the larger mother cell. We recently showed that a delay in σ(E) activation resulted in the novel phenotype of two spores (twins) forming within the same mother cell.

Loss of compartmentalization of σ(E) activity need not prevent formation of spores by Bacillus subtilis.

Compartmentalization of the activities of RNA polymerase sigma factors is a hallmark of formation of spores by Bacillus subtilis. It is initiated soon after the asymmetrically located sporulation division takes place with the activation of σ(F) in the smaller cell, the prespore. σ(F) then directs a signal via the membrane protease SpoIIGA to activate σ(E) in the larger mother cell by processing of pro-σ(E).

The pdh operon is expressed in a subpopulation of stationary-phase bacteria and is important for survival of sugar-starved Streptococcus mutans.

Streptococcus mutans is a facultative member of the oral plaque and is associated with dental caries. It is able to survive long periods of sugar starvation. We show here that inactivation of pdhD, putatively encoding a subunit of the pyruvate dehydrogenase complex, impairs survival of both batch cultures and biofilms.

Role of intracellular polysaccharide in persistence of Streptococcus mutans.

Intracellular polysaccharide (IPS) is accumulated by Streptococcus mutans when the bacteria are grown in excess sugar and can contribute toward the cariogenicity of S. mutans. Here we show that inactivation of the glgA gene (SMU1536), encoding a putative glycogen synthase, prevented accumulation of IPS.

Partial penetrance facilitates developmental evolution in bacteria.

Development normally occurs similarly in all individuals within an isogenic population, but mutations often affect the fates of individual organisms differently. This phenomenon, known as partial penetrance, has been observed in diverse developmental systems. However, it remains unclear how the underlying genetic network specifies the set of possible alternative fates and how the relative frequencies of these fates evolve.

Expression of the sigmaF-directed csfB locus prevents premature appearance of sigmaG activity during sporulation of Bacillus subtilis.

During sporulation, sigma(G) becomes active in the prespore upon the completion of engulfment. We show that the inactivation of the sigma(F)-directed csfB locus resulted in premature activation of sigma(G). CsfB exerted control distinct from but overlapping with that exerted by LonA to prevent inappropriate sigma(G) activation.

Separation of chromosome termini during sporulation of Bacillus subtilis depends on SpoIIIE.

Bacillus subtilis undergoes a highly distinctive division during spore formation. It yields two unequal cells, the mother cell and the prespore, and septum formation is completed before the origin-distal 70% of the chromosome has entered the smaller prespore. The mother cell subsequently engulfs the prespore.

Blocking chromosome translocation during sporulation of Bacillus subtilis can result in prespore-specific activation of sigmaG that is independent of sigmaE and of engulfment.

Formation of spores by Bacillus subtilis is characterized by cell compartment-specific gene expression directed by four RNA polymerase sigma factors, which are activated in the order sigma(F)-sigma(E)-sigma(G)-sigma(K). Of these, sigma(G) becomes active in the prespore upon completion of engulfment of the prespore by the mother cell. Transcription of the gene encoding sigma(G), spoIIIG, is directed in the prespore by RNA polymerase containing sigma(F) but also requires the activity of sigma(E) in the mother cell.

Control of the expression and compartmentalization of (sigma)G activity during sporulation of Bacillus subtilis by regulators of (sigma)F and (sigma)E.

During formation of spores by Bacillus subtilis the RNA polymerase factor sigma(G) ordinarily becomes active during spore formation exclusively in the prespore upon completion of engulfment of the prespore by the mother cell. Formation and activation of sigma(G) ordinarily requires prior activity of sigma(F) in the prespore and sigma(E) in the mother cell. Here we report that in spoIIA mutants lacking both sigma(F) and the anti-sigma factor SpoIIAB and in which sigma(E) is not active, sigma(G) nevertheless becomes active.

Vectors that facilitate the replacement of transcriptional lacZ fusions in Streptococcus mutans and Bacillus subtilis with fusions to gfp or gusA.

Plasmid vectors have been constructed for Streptococcus mutans and Bacillus subtilis that make possible rapid replacement of the widely used reporter gene lacZ (encoding beta-galactosidase) with either gfp (encoding green fluorescent protein) or gusA (encoding beta-glucuronidase). The lacZ-->gfp replacement vectors greatly facilitate the analysis of the spatial location of gene expression in biofilms of S. mutans and in sporulating B.

Sporulation of Bacillus subtilis.

Differentiation of vegetative Bacillus subtilis into heat resistant spores is initiated by the activation of the key transcription regulator Spo0A through the phosphorelay. Subsequent events depend on the cell compartment-specific action of a series of RNA polymerase sigma factors. Analysis of genes in the Spo0A regulon has helped delineate the mechanisms of axial chromatin formation and asymmetric division.

Persistence of Streptococcus mutans in stationary-phase batch cultures and biofilms.

Streptococcus mutans is a member of oral plaque biofilms and is considered the major etiological agent of dental caries. We have characterized the survival of S. mutans strain UA159 in both batch cultures and biofilms.

Compartmentalization of gene expression during Bacillus subtilis spore formation.

Gene expression in members of the family Bacillaceae becomes compartmentalized after the distinctive, asymmetrically located sporulation division. It involves complete compartmentalization of the activities of sporulation-specific sigma factors, sigma(F) in the prespore and then sigma(E) in the mother cell, and then later, following engulfment, sigma(G) in the prespore and then sigma(K) in the mother cell. The coupling of the activation of sigma(F) to septation and sigma(G) to engulfment is clear; the mechanisms are not.

Compartmentalization of gene expression during sporulation of Bacillus subtilis is compromised in mutants blocked at stage III of sporulation.

Mutations in the spoIIIA and spoIIIJ loci disrupt the compartmentalization of gene expression during sporulation of Bacillus subtilis. The breakdown in compartmentalization is not the cause of their being blocked in spore formation. Rather, it appears to be a consequence of the engulfed prespore's being unstable.

Contrasting effects of sigmaE on compartmentalization of sigmaF activity during sporulation of Bacillus subtilis.

Spore formation by Bacillus subtilis is a primitive form of development. In response to nutrient starvation and high cell density, B. subtilis divides asymmetrically, resulting in two cells with different sizes and cell fates.

Novel spoIIE mutation that causes uncompartmentalized sigmaF activation in Bacillus subtilis.

During sporulation, Bacillus subtilis undergoes an asymmetric division that results in two cells with different fates, the larger mother cell and the smaller forespore. The protein phosphatase SpoIIE, which is required for activation of the forespore-specific transcription factor sigma(F), is also required for optimal efficiency and timing of asymmetric division. We performed a genetic screen for spoIIE mutants that were impaired in sporulation but not sigma(F) activity and isolated a strain with the mutation spoIIEV697A.

Postdivisional synthesis of the Sporosarcina ureae DNA translocase SpoIIIE either in the mother cell or in the prespore enables Bacillus subtilis to translocate DNA from the mother cell to the prespore.

The differentiation of vegetative cells of Bacillus subtilis into spores involves asymmetric cell division, which precedes complete chromosome partitioning. The DNA translocase SpoIIIE is required to translocate the origin distal 70% of the chromosome from the larger mother cell into the smaller prespore, the two cells that result from the division. We have tested the effect of altering the time and location of SpoIIIE synthesis on spore formation.

Bex, the Bacillus subtilis homolog of the essential Escherichia coli GTPase Era, is required for normal cell division and spore formation.

The Bacillus subtilis bex gene complemented the defect in an Escherichia coli era mutant. The Bex protein showed 39 percent identity and 67 percent similarity to the E. coli Era GTPase.

Gain-of-function mutation of sapB that affects formation of alkaline phosphatase by Bacillus subtilis in sporulation conditions.

The sapB locus was defined by mutations that render sporulation alkaline phosphatase formation independent of sigma F and sigma E without affecting the temporal control of formation. The sapB locus has been cloned and sequenced. The deduced polypeptide is 232 amino acids long, with a molecular mass of 26 kDa.