Nucleotide sequence of Rhizobium meliloti GR4 insertion sequence IS Rm3 linked to the nodulation competitiveness locus nfe

Soto, Marı́a José; Zorzano, Adolfo; Olivares, José; Toro, Nicolás

doi:10.1007/bf00014498

Cited by 17 publications

(17 citation statements)

References 7 publications

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“…1, lanes 3 and 5) were also identical to the RFLP-2 pattern of vanB2 clusters found in enterococci (7). (36,39). ISRm3 belongs to the IS256 family of insertion sequences (ISs), and the vanS B2 insertion shares several characteristics with this IS family (22).…”

Section: Resultsmentioning

confidence: 99%

TransferablevanB2Tn5382-Containing Elements in Fecal Streptococcal Strains from Veal Calves

Hegstad

Sundsfjord

2003

Antimicrob Agents Chemother

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Three vancomycin-resistant veal calf fecal streptococci, identified as Streptococcus gallolyticus (n ‫؍‬ 2) and Streptococcus lutetiensis, were shown to harbor vanB2 Tn5382-like elements earlier described in enterococci. One S. gallolyticus strain had a 1,495-bp IS256-related element inserted in vanS B . The vanB2 Tn5382 element present in the plasmid-free S. lutetiensis strain was transferable to Enterococcus faecium BM4105-RF, Enterococcus faecalis JH2-2, and its recombination-deficient derivative, UV202. The transfer frequencies were comparable between recipient strains (from 1 ؋ 10 ؊7 to 7 ؋ 10 ؊6 ). All transconjugants acquired a vanB-containing chromosomal insert of approximately 100 kb, apparently by site-specific integration. Secondary transconjugants were not observed in intraspecies retransfer experiments. These observations are consistent with a conjugative, selftransmissible, integrative element that might be involved in the interspecies spread of vanB2 resistance determinants. Two JH2-2-derived transconjugants had also gained additional copies of large vanBcontaining chromosomal fragments, a process that involves unexplained mechanisms that seems to require functional host cell-dependent recombination mechanisms.The vanB gene cluster is a common cause of transferable high-level vancomycin resistance in human clinical enterococci worldwide (3,5,6,19,(31)(32)(33)40). Its origin remains unknown. The host range and mechanisms for intercellular spread are only partially understood. Enterococcus faecium and Enterococcus faecalis are the main enterococcal hosts, but vanB has also been described in Enterococcus gallinarum (16,35) and Enterococcus durans (18). Nonenterococcal reservoirs have also been reported, such as three fecal veal calf strains of Streptococcus gallolyticus (25) and one human fecal Streptococcus bovis isolate (27). Recently, the vanB2 gene cluster was identified in a human fecal Eggerthella lenta-related strain and in a nonidentified human fecal Clostridium species (37).The vanB operons described so far seem to have a conserved order of genes (vanR B , vanS B , vanY B , vanW, vanH B , vanB, and vanX B ). Due to sequence diversity, they can be divided in at least three distinct subtypes, vanB1 to B3, indicating different origins (7,8,11,24).Intra-and interspecies transfer of the vanB operon has been linked to the movement of large (90 to 250 kb) chromosomal fragments or conjugative plasmids (3,5,6,(31)(32)(33)40). Recently, the 34-kb vanB2-containing Tn1549, which is similar to the Tn916-Tn1545 family of conjugative transposons, was completely sequenced (11). Tn1549 appears to be similar to the earlier described and partially sequenced Tn5382 (3). These putative conjugative transposons are thus designated Tn5382-like. Several studies suggest that the vanB2 operon is the most prevalent vanB subtype and that it is universally present as an integral part of Tn5382-like elements (5, 11, 23). Although molecular evidence for precise chromosomal or plasmid insertions of a vanB2 Tn5382-like elem...

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Section: Resultsmentioning

confidence: 99%

TransferablevanB2Tn5382-Containing Elements in Fecal Streptococcal Strains from Veal Calves

Hegstad

Sundsfjord

2003

Antimicrob Agents Chemother

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“…Nodulation efficiency loci, referred to as nfe, were first identified in R. meliloti and later in B. japonicurn (Chun and Stacey, 1994;Sanjuan and Olivares, 1991;Soto et al, 1992Soto et al, , 1993. Mutations in this locus cause delayed nodulation and a decrease in nodule number.…”

Section: Nodulation Efficiency Loci Nfementioning

confidence: 99%

Toward More Productive, Efficient, and Competitive Nitrogen-Fixing Symbiotic Bacteria

Maier

Triplett

1996

Critical Reviews in Plant Sciences

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The prospects of developing strains of legume nodule bacteria that provide higher productivity of leguminous plants are described. The generic, biochemical, physiological, regulatory, and economic constraints that govern the ability of private and public efforts to construct better inoculants for legume nodulation are discussed. Success in constructing better inoculants requires a two-pronged approach. First, strains need to be improved in order to compete successfully with indigenous strains for root nodulation of legumes. Several loci have been identified to date that affect competitiveness for strain nodule occupancy. Usually mutations in these loci affect the ability of a strain to form nodules rapidly and efficiently. Other loci, such as those that confer antibiotic production, can be added to strains to enhance nodulation competitiveness when co-inoculated with antibiotic-sensitive strains. Second, the inoculum strains must be improved with respect to symbiotic nitrogen fixation. Efforts to enhance the symbiotic productivity of legume nodule bacteria either by mutation or genetic engineering are also described. The best characterized example of these is the hydrogenase system. Due to nitrogenase-dependent catalysis of proton reduction, diazotrophs evolve large amounts of H,. An approach to maximize the efficiency of symbiotic N, fixation, and therefore of legume productivity, is to construct strains of Rhizobium with the ability to oxidize this otherwise wasted H,. The electrons produced by H, oxidation are funneled through energy-conserving electron transport chains. Our knowledge of the genetics and biochemistry of H, oxidation in Bradyrhizobium japonicum and Rhizobium leguminosarum has developed rapidly in recent years. At least 20 genes are needed for these bacteria to manufacture and efficiently express a nickel-containing H,-uptake hydrogenase. These genes include those encoding regulatory elements, posttranslational processing enzymes, nickel-sensing and nickel-metabolism proteins, and electron transport components for integrating the electrons from H, oxidation into the respiratory chain. Some of the components for oxidizing H, in the symbiotic N, fixing bacteria are distinct from the analogous components in (nonsymbiotic) H, oxidizing bacteria.

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“…The nfe region located on the non-symbiotic plasmid pRmeGR4b is rich in various IS elements: ISRm3 [19] and ISRm4 [20] are located to the right side of nfeD [17] at 128 bp and 2.5 kb, respectively; whereas ISRm6 is localised 4.3 kb to the left side of nfeD [21]. Eleven kb to the right side of the former loci, a new S. meliloti IS element has been recently identi¢ed and designated ISRm8.…”

Section: Resultsmentioning

confidence: 99%

The Sinorhizobium meliloti insertion sequence (IS) elements ISRm102F34-1/ISRm7 and ISRm220-13-5 belong to a new family of insertion sequence elements

Selbitschka

1999

FEMS Microbiology Letters

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The Sinorhizobium meliloti insertion sequence (IS) elements ISRm102F34-1 and ISRm220-13-5 are 1481 and 1550 base pairs (bp) in size, respectively. ISRm102F34-1 is bordered by 15 bp imperfect terminal inverted repeat sequences (two mismatches), whereas the terminal inverted repeat of ISRm220-13-5 has a length of 16 bp (two mismatches). Both insertion sequence elements generate a 6-bp target duplication upon transposition. The putative transposase enzymes of ISRm102F34-1 and ISRm220-13-5 consist of 449 or 448 amino acid residues with predicted molecular weights of 50.7 or 51.3 kDa and theoretical isoelectric points of 10.8 or 11.1, respectively. ISRm102F34-1 is identical in 98.9% of its nucleotide sequence to an apparently inactive copy of an insertion sequence element, designated ISRm7, which flanks the left-end of the nodule formation efficiency (nfe) region of plasmid pRmeGR4b of S. meliloti strain GR4. ISRm102F34-1 and ISRm220-13-5 are closely related since they show an overall identity of 57.0% at the nucleotide sequence level and of 47.3% at the deduced amino acid level of their putative transposases. Both insertion sequence elements displayed significant similarity to the Xanthomonas campestris ISXc6 and its homolog IS1478a. Since none of these insertion sequence elements could be allocated to existing families of insertion sequence elements, a new family is proposed. Analysis of the distribution of ISRm102F34-1/ISRm7 in various local S. meliloti populations sampled from Medicago sativa, Medicago sphaerocarpa and Melilotus alba host plants at different locations in Spain revealed its presence in 35% of the isolates with a copy number ranging from 1 to 5. Furthermore, ISRm102F34-1/ISRm7 homologs were identified in other rhizobial species. z

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Nucleotide sequence of Rhizobium meliloti GR4 insertion sequence IS Rm3 linked to the nodulation competitiveness locus nfe

Cited by 17 publications

References 7 publications

TransferablevanB2Tn5382-Containing Elements in Fecal Streptococcal Strains from Veal Calves

TransferablevanB2Tn5382-Containing Elements in Fecal Streptococcal Strains from Veal Calves

Toward More Productive, Efficient, and Competitive Nitrogen-Fixing Symbiotic Bacteria

The Sinorhizobium meliloti insertion sequence (IS) elements ISRm102F34-1/ISRm7 and ISRm220-13-5 belong to a new family of insertion sequence elements

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