title: Construction of a recA mutant of Azospirillum lipoferum and involvement of recA in phase variation.
abstract: The plant-growth promoting rhizobacterium Azospirillum lipoferum strain 4B generates in vitro a stable phase variant designated 4VI at frequencies of 10(-4) to 10(-3) per cell per generation. Variant 4VI displays pleitropic modifications, such as the loss of swimming motility and the inability to assimilate certain sugars compared to the wild type. The mechanism underlying phase variation is unknown. To determine whether RecA-mediated processes are involved in phase variation, the recA gene of A. lipoferum 4B was cloned and sequenced and a recA mutant (termed 4BrecA) was constructed by allelic exchange. Strain 4BrecA showed increased sensitivity to UV and MMS compared with 4B and impaired recombinase activity. The ability to generate variants in vitro was not altered; the variants from 4BrecA exhibited all morphological and biochemical features characteristic of the variant generated by strain 4B. However, the frequency of variants generated by 4BrecA was increased by up to 10-fold. So, in contrast with many studies showing the abolition or a large reduction of the frequency of phase variation in recA mutants, this study describes an enhancement of phase variation in the absence of a functional recA.
authors.affiliation: UMR CNRS 5557 Ecologie Microbienne, Université Claude Bernard Lyon1, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Vial
authors.forename: Joël F
authors.initials: JF
authors.lastname: Pothier
authors.forename: Philippe
authors.initials: P
authors.lastname: Normand
authors.forename: Yvan
authors.initials: Y
authors.lastname: Moënne-Loccoz
authors.forename: René
authors.initials: R
authors.lastname: Bally
authors.forename: Florence
authors.initials: F
authors.lastname: Wisniewski-Dyé
mesh_terms: D000595:Amino Acid Sequence; D042081:Azospirillum lipoferum / Q000187:drug effects / Q000235:genetics* / Q000502:physiology* / Q000528:radiation effects; D050260:Carbohydrate Metabolism; D003001:Cloning, Molecular; D004396:Coloring Agents / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D005798:Genes, Bacterial; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008969:Molecular Sequence Data; D009068:Movement; D016254:Mutagenesis, Insertional; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014466:Ultraviolet Rays
chemical_list: D004396:Coloring Agents; D004269:DNA, Bacterial; D009153:Mutagens; D008741:Methyl Methanesulfonate; D011938:Rec A Recombinases