title: Glycerol utilization by Rhizobium leguminosarum requires an ABC transporter and affects competition for nodulation.
abstract: Plasmid curing has shown that the ability to use glycerol as a carbon source is plasmid-encoded in Rhizobium leguminosarum. We isolated the locus responsible for glycerol utilization from plasmid pRleVF39c in R. leguminosarum bv. viciae VF39. This region was analyzed by DNA sequencing and mutagenesis. The locus encompasses a gene encoding GlpR (a DeoR regulator), genes encoding an ABC transporter, and genes glpK and glpD, encoding a kinase and dehydrogenase, respectively. All the genes except the regulatory gene glpR were organized into a single operon, and were required for growth on glycerol. The glp operon was strongly induced by both glycerol and glycerol 3-phosphate, as well as by pea seed exudate. GlpR repressed the operon in the absence of inducer. Mutation of genes encoding the ABC transporter abolished all transport of glycerol in transport assays using radiolabelled glycerol. This confirms that, unlike in other organisms such as Escherichia coli and Pseudomonas aeruginosa, which use facilitated diffusion, glycerol uptake occurs by an active process in R. leguminosarum. Since the glp locus is highly conserved in all sequenced R. leguminosarum and Rhizobium etli strains, as well as in Sinorhizobium spp. and Agrobacterium spp. and other alphaproteobacteria, this process for glycerol uptake is probably widespread. Mutants unable to use glycerol were deficient in competitiveness for nodulation of peas compared with the wild-type, suggesting that glycerol catabolism confers an advantage upon the bacterium in the rhizosphere or in the infection thread.
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
authors.forename: Hao
authors.initials: H
authors.lastname: Ding
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Yip
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Barney A
authors.initials: BA
authors.lastname: Geddes
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Oresnik
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hynes
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005990:Glycerol / Q000378:metabolism*; D005991:Glycerol Kinase / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009876:Operon; D018532:Pisum sativum / Q000382:microbiology; D055170:Plant Root Nodulation; D010957:Plasmids; D012097:Repressor Proteins / Q000378:metabolism; D016961:Rhizobium leguminosarum / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017422:Sequence Analysis, DNA
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005994:Glycerophosphates; D012097:Repressor Proteins; C029620:alpha-glycerophosphoric acid; D005991:Glycerol Kinase; D005990:Glycerol