title: Chromosome loss from par mutants of Pseudomonas putida depends on growth medium and phase of growth.
abstract: The proteins encoded by chromosomal homologues of the parA and parB genes of many bacterial plasmids have been implicated in chromosome partitioning. Unlike their plasmid counterparts, mutant phenotypes produced by deleting these genes have so far been elusive or weakly expressed, except during sporulation. Here the properties of Pseudomonas putida strains with mutations in parA and parB are described. These mutants do not give rise to elevated levels of anucleate bacteria when grown in rich medium under standard conditions. However, in M9-minimal medium different parA and parB mutations gave between 5 and 10% anucleate cells during the transition from exponential phase to stationary phase. Comparison of the DNA content of bacteria at different stages of the growth curve, in batch culture in L-broth and in M9-minimal medium, suggests that the par genes are particularly important for chromosome partitioning when cell division reduces the chromosome copy number per cell from two to one. This transition occurs in P. putida during the entry into stationary phase in M9-minimal medium, but not in L-broth. It is proposed that the partition apparatus is important to ensure proper chromosome segregation primarily when the bacteria are undergoing cell division in the absence of ongoing DNA replication.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK1.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lewis
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK1.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Bignell
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK1.
authors.forename: Wei
authors.initials: W
authors.lastname: Zeng
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK1.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Jones
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK1.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Thomas
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000235:genetics; D003470:Culture Media; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D016958:Pseudomonas putida / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; C052883:chromosome partition proteins, bacterial