Regulation of Escherichia coli cell division genes ftsA and ftsZ by the two-component system rcsC-rcsB

Genes rcsC and rcsB form a two-component system in which rcsC encodes the sensor element and rcsB the regulator. In Escherichia coli, the system positively regulates the expression of the capsule operon, cps, and of the cell division gene ftsZ. We report the identification of the promoter and of the sequences required for rcsB-dependent stimulation of ftsZ expression. The promoter, ftsA1p, located in the ftsQ coding sequence, co-regulates ftsA and ftsZ. The sequences required for rcsB activity are immediately adjacent to this promoter.     

Inhibition of growth of ftsQ, ftsA, and ftsZ mutant cells of Escherichia coli by amplification of a chromosomal region encompassing closely aligned cell division and cell growth genes.

Amplification of a 2.6-kilobase chromosomal fragment of the mra region of Escherichia coli encompassing the ftsI(pbpB) gene and an open reading frame upstream with lethal to E. coli strains with mutations of the flanking cell division genes ftsQ, ftsA, and ftsZ. A shortened fragment in which the major portion of ftsI was deleted also had lethal effects on ftsQ and ftsZ mutants.     

Identification of new genes in a cell envelope-cell division gene cluster of Escherichia coli: cell division gene ftsQ.

We report the identification, cloning, and mapping of a new cell division gene, ftsQ. This gene formed part of a cluster of three division genes (in the order ftsQ ftsA ftsZ) which itself formed part of a larger cluster of at least 10 genes, all of which were involved in some step in cell division, cell envelope synthesis, or both. The ftsQAZ group was transcribed from at least two independent promoters.     

Impaired cell division and sporulation of a Bacillus subtilis strain with the ftsA gene deleted.

The ftsZ and ftsA genes of Bacillus subtilis are organized in a simple operon expressed from promoter sequences immediately upstream of ftsA. The promoter-distal ftsZ gene is an essential septation gene. In this report, it is shown that the promoter-proximal ftsA gene can be deleted in a previously constructed strain in which the essential gene, ftsZ, is under the control of the inducible spac promoter. Absence of the ftsA gene product resulted in a very filamentous morphology indicating an important role for ftsA in cell division. Also, growth was severely impaired, and viability and sporulation were reduced. The defective sporulation phenotype correlated with a deficiency in the processing of pro-sigma E to its active form.     

Inactivation of essential division genes, ftsA, ftsZ, suppresses mutations at sfiB, a locus mediating division inhibition during the SOS response in E. coli.

A dominant sfiB allele has been cloned which renders partial diploids of an sfiB + Escherichia coli host resistant to division inhibition mediated by the SOS response. Transpositional mutagenesis was used to map the position of this sfiB114 allele, carried by a plasmid pLG552 , to an approximately 0.6-kb region overlapping the coding regions for ftsA and ftsZ , two genes essential for normal division. Most Tn 1000 insertions which inactivated sfiB114 also inactivated the ftsA function and caused the disappearance of both a 47-K polypeptide and reduced levels of a 42-K polypeptide in maxi-cells carrying pLG552 . An additional insertion inactivating sfiB114 was mapped to the right of ftsA and resulted in loss of the 42-K but not the 47-K polypeptide in maxi-cells. Moreover, a 2.1-kb BamHI-EcoRI DNA fragment was subcloned which carried ftsA and coded for a 47-K polypeptide but did not carry sfiB114 and did not complement ftsZ . We conclude that sfiB114 is located within ftsZ coding for a 42-K polypeptide. Nevertheless, insertions into ftsZ coding the 47-K polypeptide suppress the sfiB114 allele by substantially reducing the synthesis of the FtsZ ( SfiB114 ) polypeptide. The level of residual FtsZ synthesis was minimal when Tn 1000 was inserted closest to the distal end of ftsA , indicating the presence of a regulatory region essential for maximal expression of ftsZ .     

Complete nucleotide sequence of the Escherichia coli recB gene.

The complete nucleotide sequence of the Escherichia coli recB gene which encodes a subunit of the ATP-dependent DNase, Exonuclease V, has been determined. The proposed coding region for the RecB protein is 3543 nucleotides long and would encode a polypeptide of 1180 amino acids with a calculated molecular weight of 133,973. The start of the recB coding sequence overlaps the 3' end of the upstream ptr gene, and the recB termination codon overlaps the initiation codon of the downstream recD gene, suggesting that these genes may form an operon. No sequences which reasonably fit the consensus for an E. coli promoter could be identified upstream of the proposed recB translational start. The predicted RecB amino acid sequence contains regions of homology with ATPases, DNA binding proteins and DNA repair enzymes.     

Cloning and characterization of Bacillus subtilis homologs of Escherichia coli cell division genes ftsZ and ftsA.

The Bacillus subtilis homolog of the Escherichia coli ftsZ gene was isolated by screening a B. subtilis genomic library with anti-E. coli FtsZ antiserum. DNA sequence analysis of a 4-kilobase region revealed three open reading frames. One of these coded for a protein that was about 50% homologous to the E. coli FtsZ protein. The open reading frame just upstream of ftsZ coded for a protein that was 34% homologous to the E. coli FtsA protein. The open reading frames flanking these two B. subtilis genes showed no relationship to those found in E. coli. Expression of the B. subtilis ftsZ and ftsA genes in E. coli was lethal, since neither of these genes could be cloned on plasmid vectors unless promoter sequences were first removed. Cloning the B. subtilis ftsZ gene under the control of the lac promoter resulted in an IPTGs phenotype that could be suppressed by overproduction of E. coli FtsZ. These genes mapped at 135 degrees on the B. subtilis genetic map near previously identified cell division mutations.     

The cell wall and cell division gene cluster in the Mra operon of Pseudomonas aeruginosa: cloning, production, and purification of active enzymes

We have cloned the Pseudomonas aeruginosa cell wall biosynthesis and cell division gene cluster that corresponds to the mra operon in the 2-min region of the Escherichia coli chromosome. The organization of the two chromosomal regions in P. aeruginosa and E. coli is remarkably similar with the following gene order: pbp3/pbpB, murE, murF, mraY, murD, ftsW, murG, murC, ddlB, ftsQ, ftsA, ftsZ, and envA/LpxC. All of the above P. aeruginosa genes are transcribed from the same strand of DNA with very small, if any, intragenic regions, indicating that these genes may constitute a single operon. All five amino acid ligases, MurC, MurD, MurE, MurF, and DdlB, in addition to MurG and MraY were cloned in expression vectors. The four recombinant P. aeruginosa Mur ligases, MurC, MurD, MurE, and MurF were overproduced in E. coli and purified as active enzymes.     

The proper ratio of FtsZ to FtsA is required for cell division to occur in Escherichia coli.

Interactions among cell division genes in Escherichia coli were investigated by examining the effect on cell division of increasing the expression of the ftsZ, ftsA, or ftsQ genes. We determined that cell division was quite sensitive to the levels of FtsZ and FtsA but much less so to FtsQ. Inhibition of cell division due to an increase in FtsZ could be suppressed by an increase in FtsA. Inhibition of cell division due to increased FtsA could be suppressed by an increase in FtsZ. In addition, although wild-type strains were relatively insensitive to overexpression of ftsQ, we observed that cell division was sensitized to ftsQ overexpression in ftsI, ftsA, and ftsZ mutants. Among these, the ftsI mutant was the most sensitive. These results suggest that these gene products may interact and that the proper ratio of FtsZ to FtsA is critical for cell division to occur.