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The divIVB region of the Bacillus subtilis chromosome encodes homologs of Escherichia coli septum placement (minCD) and cell shape (mreBCD) determinants.

ABSTRACT: Mutation of the divIVB locus in Bacillus subtilis causes frequent misplacement of the division septum, resulting in circular minicells, short rods, and filaments of various sizes. The divIVB1 mutant allele maps to a region of the chromosome also known to encode sporulation (spo0B, spoIVF, spoIIB) and cell shape (rodB) determinants. This study reports the cloning and sequence analysis of 4.4 kb of the B. subtilis chromosome encompassing the divIVB locus. This region contains five open reading frames (ORFs) arranged in two functionally distinct gene clusters (mre and min) and transcribed colinearly with the direction of replication. Although sequence analysis reveals potential promoters preceding each gene cluster, studies with integrational plasmids suggest that all five ORFs are part of a single transcription unit. The first gene cluster contains three ORFs (mreBCD) homologous to the mre genes of Escherichia coli. We show that rodB1 is allelic to mreD and identify the rodB1 mutation. The second gene cluster contains two ORFs (minCD) homologous to minC and minD of E. coli but lacks a minE homolog. We show that divIVB1 is allelic to minD and identify two mutations in the divIVB1 allele. Insertional inactivation of either minC or minD or the presence of the divIVB region on plasmids produces a severe minicell phenotype in wild-type cells. Moreover, E. coli cells carrying the divIVB region on a low-copy-number plasmid produce minicells, suggesting that a product of this locus may retain some function across species boundaries.

SUBMITTER: Varley AW

PROVIDER: S-EPMC207348 | biostudies-other | 1992 Nov

REPOSITORIES: biostudies-other

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The divIVB region of the Bacillus subtilis chromosome encodes homologs of Escherichia coli septum placement (minCD) and cell shape (mreBCD) determinants.

Varley A W AW Stewart G C GC

Journal of bacteriology 19921101 21

Mutation of the divIVB locus in Bacillus subtilis causes frequent misplacement of the division septum, resulting in circular minicells, short rods, and filaments of various sizes. The divIVB1 mutant allele maps to a region of the chromosome also known to encode sporulation (spo0B, spoIVF, spoIIB) and cell shape (rodB) determinants. This study reports the cloning and sequence analysis of 4.4 kb of the B. subtilis chromosome encompassing the divIVB locus. This region contains five open reading fra ...[more]

PMID: 1400225

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Project description:Bacillus subtilis is a bacterium capable of differentiating into a spore form more resistant to environmental stress. Early in sporulation, each cell possesses two copies of a circular chromosome. A polar FtsZ ring (Z ring) directs septation over one of the chromosomes, generating two cell compartments. The smaller "forespore" compartment initially contains only 25 to 30% of one chromosome, and this transient genetic asymmetry is required for differentiation. Timely assembly of polar Z rings and precise capture of the chromosome in the forespore both require the DNA-binding protein RefZ. To mediate its role in chromosome capture, RefZ must bind to specific DNA motifs (RBMs) that localize near the poles at the time of septation. Cells artificially induced to express RefZ during vegetative growth cannot assemble Z rings, an effect that also requires DNA binding. We hypothesized that RefZ-RBM complexes mediate precise chromosome capture by modulating FtsZ function. To investigate, we isolated 10 RefZ loss-of-function (rLOF) variants unable to inhibit cell division yet still capable of binding RBMs. Sporulating cells expressing the rLOF variants in place of wild-type RefZ phenocopied a ΔrefZ mutant, suggesting that RefZ acts through an FtsZ-dependent mechanism. The crystal structure of RefZ was solved, and wild-type RefZ and the rLOF variants were further characterized. Our data suggest that RefZ's oligomerization state and specificity for the RBMs are critical determinants influencing RefZ's ability to affect FtsZ dynamics. We propose that RBM-bound RefZ complexes function as a developmentally regulated nucleoid occlusion system for fine-tuning the position of the septum relative to the chromosome during sporulation.IMPORTANCE The bacterial nucleoid forms a large, highly organized structure. Thus, in addition to storing the genetic code, the nucleoid harbors positional information that can be leveraged by DNA-binding proteins to spatially constrain cellular activities. During B. subtilis sporulation, the nucleoid undergoes reorganization, and the cell division protein FtsZ assembles polarly to direct septation over one chromosome. The TetR family protein RefZ binds DNA motifs (RBMs) localized near the poles at the time of division and is required for both timely FtsZ assembly and precise capture of DNA in the future spore compartment. Our data suggest that RefZ exploits nucleoid organization by associating with polarly localized RBMs to modulate the positioning of FtsZ relative to the chromosome during sporulation.

Dataset Information

The divIVB region of the Bacillus subtilis chromosome encodes homologs of Escherichia coli septum placement (minCD) and cell shape (mreBCD) determinants.

Publications

The divIVB region of the Bacillus subtilis chromosome encodes homologs of Escherichia coli septum placement (minCD) and cell shape (mreBCD) determinants.

Similar Datasets

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