PMID:2176633

Citation	Trun, NJ and Gottesman, S (1990) On the bacterial cell cycle: Escherichia coli mutants with altered ploidy.Genes Dev. 4:2036-47
Abstract	We describe a scheme for isolation of new classes of mutants in the cell cycle of Escherichia coli. The mutants were selected as resistant to camphor vapors, which results in increased ploidy, and were subsequently screened for an increase in cell density and an increase in the gene dosage of the lac operon. Our mutations are located at four different places in the chromosome; we have named these loci mbr (moth ball resistant). mbrA maps to 68 min on the E. coli chromosome, mbrB to 88.5 min, mbrC to 89.5 min, and mbrD to 90 min. mbrD mutations may be alleles of rpoB (a subunit of RNA polymerase). In addition to the selected or screened phenotypes, most of the mutants fail to grow on rich media or at high temperatures. We have examined the nine mutants under nonpermissive conditions, using several techniques to determine the cause of death. We have also coupled our mutations with lesions in dnaA, which is required for cell-cycle-specific DNA replication, and rnh (the gene for RNase H), which is required for specificity in the DNA initiation reaction, and determined the effects of the double and triple mutants under permissive and nonpermissive conditions. These tests have shown that bacteria mutated at mbrA do not tolerate a null mutation in rnh, indicating that they are dependent on DNA replication initiating at oriC. In contrast, mutations at mbrB, mbrC, and mbrD exhibit their phenotypes independent of oriC initiation of DNA replication, suggesting that the mutations affect factors that influence the DNA/cell ratio regardless of the origin of DNA replication. Based on our results, the mbr mutations appear to have defects in cell-cycle timing and/or defects in chromosomal partitioning.
Links	PubMed
Keywords	Camphor; Cell Cycle; Chromosome Mapping; Chromosomes, Bacterial; DNA Replication; DNA, Bacterial; DNA-Directed RNA Polymerases; Drug Resistance, Microbial; Endoribonucleases; Escherichia coli; Mutation; Phenotype; Ploidies; Ribonuclease H
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Phenotype Annotations

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Phenotype of	Taxon Information	Genotype Information (if known)	Condition Information	OMP ID	OMP Term Name	ECO ID	ECO Term Name	Notes	Status
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: mrbA Genotype of Experimental Strain : mrbA4	Reference Condition:	OMP:0000276	increased resistance to antibiotics	ECO:0000182	in vitro culture assay data	camphor resistance
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: mrbA Genotype of Experimental Strain : mrbA15	Reference Condition:	OMP:0000276	increased resistance to antibiotics	ECO:0000182	in vitro culture assay data	Resistant to camphor
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: mbrC Genotype of Experimental Strain : mbrC11	Reference Condition:	OMP:0000276	increased resistance to antibiotics	ECO:0000182	in vitro culture assay data	Camphor Resistance
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 8333	Genotype of Reference Strain: mbrD Genotype of Experimental Strain : mbrD3	Reference Condition:	OMP:0000276	increased resistance to antibiotics	ECO:0000182	in vitro culture assay data	Camphor Resistance, Several other similar phenotype mutants are described
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 8333	Genotype of Reference Strain: mbrD Genotype of Experimental Strain : mbrD7	Reference Condition:	OMP:0000276	increased resistance to antibiotics	ECO:0000182	in vitro culture assay data	Resistance to camphor, other mutants with similar phenotypes are described
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