Induction of Symbiotically Defective Auxotrophic Mutants of Rhizobium fredii HH303 by Transposon Mutagenesis †
AUTOR(ES)
Kim, Choong-Hyun
RESUMO
Symbiotically defective auxotrophic mutants were isolated by transposon Tn5 mutagenesis of Rhizobium fredii HH303, a fast-growing microsymbiont of North American commercial soybean cultivars such as Glycine max cv. Williams. Three different Tn5-carrying suicide vectors, pBLK1-2, pSUP1011, and pGS9, were used for mutagenesis with transposition frequencies of 4 × 10−5, 3 × 10−6, and 1 × 10−6, respectively, while the frequency of background mutation resistant to 500 μg of kanamycin per ml was 1 × 10−8. From 2,600 Tn5-induced mutants, 14 auxotrophic mutants were isolated and classified in seven groups including adenosine (four), aspartate (two), cysteine or methionine (two), isoleucine and valine (two), nicotinic acid (one), pantothenic acid (one), and uracil (two). All the auxotrophs induced nodulation on soybean, but the symbiotic effectiveness of each mutant was different. Three auxotrophs (two cysteine or methionine and one pantothenic acid) formed effective nodules similar to those of the wild type. Three auxotrophs (one nicotinic acid and two aspartate) produced mature nodules like those of the wild type, but the nodules lacked the characteristic pink color inside and were unable to fix nitrogen. Four auxotrophs (two adenosine and two uracil) induced pseudonodules unable to fix nitrogen. The other four auxotrophs repeatedly induced both effective and ineffective nodules, but bacteroids isolated from the effective nodules were prototrophic revertants. The symbiotic phenotype and the degree of effectiveness of the auxotrophic mutants varied with the type of mutation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=202467Documentos Relacionados
- Exopolysaccharide-Deficient Mutants of Rhizobium fredii HH303 Which Are Symbiotically Effective
- Isolation of competition-defective mutants of Rhizobium fredii.
- Physical and genetic characterization of symbiotic and auxotrophic mutants of Rhizobium meliloti induced by transposon Tn5 mutagenesis.
- Isolation of Rhodospirillum centenum Mutants Defective in Phototactic Colony Motility by Transposon Mutagenesis
- In vivo growth characteristics of leucine and methionine auxotrophic mutants of Mycobacterium bovis BCG generated by transposon mutagenesis.