Long-term Impact of sewage sludge application on rhizobium leguminosarum biovar trifolii: an evaluation using meta-analysis

The Long-Term Sludge Experiment (LTSE) began in 1994 at nine UK field sites as part of continuing research into the effects of sludge-borne heavy metals on soil fertility. The long-term effects of Zn, Cu, and Cd on the most probable numbers of cells (MPN) of Rhizobium leguminosarum biovar trifolii were monitored for 8 yr in sludge-amended soils. To assess the statutory limits set by the UK Sludge (Use in Agriculture) Regulations, the experimental data were reviewed using statistical methods of meta-analysis. Previous LTSE studies have focused predominantly on statistical significance rather than effect size, whereas meta-analysis focuses on the magnitude and direction of an effect, i.e., the practical significance rather than its statistical significance. Results showed Zn to be the most toxic element causing an overall significant decrease in Rhizobium MPN of −26.6% during the LTSE. The effect of Cu showed no significant effect on Rhizobium MPN at concentrations below the UK limits, although a −5% decrease in Rhizobium MPN was observed in soils where total Cu ranged from 100 to <135 mg kg−1. Overall, there was nothing to indicate that Cd had a significant effect on Rhizobium MPN below the current UK statutory limit. In summary, the UK statutory limit for Zn appears to be insufficient for protecting Rhizobium from Zn toxicity effects

Permanent Draft Genome Sequence of the French Bean Symbiont Rhizobium sp. Strain RSm-3 Isolated from the Eastern Himalayan Region of India

The genus Rhizobium contains many species able to form nitrogen-fixing nodules on plants of the legume family. Here, we report the 6.9-Mbp draft genome sequence of Rhizobium sp. strain RSm-3, with a G+C content of 61.4% and 6,511 candidate protein-coding genes

Average nucleotide identity of genome sequences supports the description of Rhizobium lentis sp. nov., Rhizobium bangladeshense sp. nov. and Rhizobium binae sp. nov. from lentil (Lens culinaris) nodules

Rhizobial strains isolated from effective root nodules of field-grown lentil (Lens culinaris) from different parts of Bangladesh were previously analysed using sequences of the 16S rRNA gene, three housekeeping genes (recA, atpD and glnll) and three nodulation genes (nodA, nodC and nodD), DNA fingerprinting and phenotypic characterization. Analysis of housekeeping gene sequences and DNA fingerprints indicated that the strains belonged to three novel clades in the genus Rhizobium. In present study, a representative strain from each clade was further characterized by determination of cellular fatty acid compositions, carbon substrate utilization patterns and DNA DNA hybridization and average nucleotide identity (ANI) analyses from whole-genome sequences. DNA DNA hybridization showed 50-62 % relatedness to their closest relatives (the type strains of Rhizobium etli and Rhizobium phaseoh) and 50-60 % relatedness to each other. These results were further supported by ANI values, based on genome sequencing, which were 87-92 % with their close relatives and 88-89 % with each other. On the basis of these results, three novel species, Rhizobium lentis sp. nov. (type strain BLR27(T)=LMG 28441(T)=DSM 29286(T)), Rhizobium bangladeshense sp. nov. (type strain BLR175(T)=LMG 28442(T)=DSM 29287(T)) and Rhizobium binae sp. nov. (type strain BLR195(T)=LMG 28443(T)=DSM 29288(T)), are proposed. These species share common nodulation genes (nodA, nodC and nodD) that are similar to those of the symbiovar viciae

chemotaxis of rhizobium phaseoli towards flavones and other related compounds

The formation of nitrogen-fixing nodules on leguminous plants is the result of a highly specific interaction between the host plant and the soil bacterium Rhizobium. Two observations suggest that chemotaxis may play a role in the establishment of the legume-Rhizobium symbiosis: 1) The widespread occurence of Rhizobium species with flagella (Gotz, 1982; Carlile. 1980)2) The copious exudation into the soil surrounding legume roots of a wide variety of potentially chemotactic compounds which include amino acids, sugars and sugar-acids. (Beringer et.al.,1979). Recently the plant flavones luteolin (3,44,7 - Tetra - hydroxyflavone) and apigenin (4,5,7 - Trihydroxy-flavone) have been reported as inducers of Rhizobium nodulation genes (Peters, 1986, Rolfe 1986). We report here that R. phaseoli (RP8002) exhibits positive chemotaxis toward both flavones. Other diverse compounds tested elicited different responses. An understanding of the influence of flavones in two events such as chemotaxis and nodulation efficiency can be valuable to clarify their action in the intricate legume-rhizobia interaction

Permanent Draft Genome Sequence of Rhizobium sp. Strain LCM 4573, a Salt-Tolerant, Nitrogen-Fixing Bacterium Isolated from Senegalese Soils

The genus Rhizobium contains many species that are able to form nitrogen-fixing nodules on plants of the legume family. Here, we report the 5.5-Mb draft genome sequence of the salt-tolerant Rhizobium sp. strain LCM 4573, which has a G+C content of 61.2% and 5,356 candidate protein-encoding genes

Characterization of Rhizobium grahamii extrachromosomal replicons and their transfer among rhizobia

Background Rhizobium grahamii belongs to a new phylogenetic group of rhizobia together with Rhizobium mesoamericanum and other species. R. grahamii has a broad-host-range that includes Leucaena leucocephala and Phaseolus vulgaris, although it is a poor competitor for P. vulgaris nodulation in the presence of Rhizobium etli or Rhizobium phaseoli strains. This work analyzed the genome sequence and transfer properties of R. grahamii plasmids. Results Genome sequence was obtained from R. grahamii CCGE502 type strain isolated from Dalea leporina in Mexico. The CCGE502 genome comprises one chromosome and two extrachromosomal replicons (ERs), pRgrCCGE502a and pRgrCCGE502b. Additionally, a plasmid integrated in the CCGE502 chromosome was found. The genomic comparison of ERs from this group showed that gene content is more variable than average nucleotide identity (ANI). Well conserved nod and nif genes were found in R. grahamii and R. mesoamericanum with some differences. R. phaseoli Ch24-10 genes expressed in bacterial cells in roots were found to be conserved in pRgrCCGE502b. Regarding conjugative transfer we were unable to transfer the R. grahamii CCGE502 symbiotic plasmid and its megaplasmid to other rhizobial hosts but we could transfer the symbiotic plasmid to Agrobacterium tumefaciens with transfer dependent on homoserine lactones. Conclusion Variable degrees of nucleotide identity and gene content conservation were found among the different R. grahamii CCGE502 replicons in comparison to R. mesoamericanum genomes. The extrachromosomal replicons from R. grahamii were more similar to those found in phylogenetically related Rhizobium species. However, limited similarities of R. grahamii CCGE502 symbiotic plasmid and megaplasmid were observed in other more distant Rhizobium species. The set of conserved genes in R. grahamii comprises some of those that are highly expressed in R. phaseoli on plant roots, suggesting that they play an important role in root colonization.Fil: Althabegoiti, Maria Julia. Universidad Nacional Autónoma de México; México. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ormeño Orrillo, Ernesto. Universidad Nacional Autónoma de México; MéxicoFil: Lozano, Luis. Universidad Nacional Autónoma de México; MéxicoFil: Torres Tejerizo, Gonzalo Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional Autónoma de México; MéxicoFil: Rogel, Marco Antonio. Universidad Nacional Autónoma de México; MéxicoFil: Mora, Jaime. Universidad Nacional Autónoma de México; MéxicoFil: Martinez Romero, Esperanza. Universidad Nacional Autónoma de México; Méxic

Phylogenies of atpD and recA support the small subunit rRNA-based classification of rhizobia

The current classification of the rhizobia (root-nodule symbionts) assigns them to six genera. It is strongly influenced by the small subunit (16S, SSU) rRNA molecular phylogeny, but such single-gene phylogenies may not reflect the evolution of the genome as a whole. To test this, parts of the atpD and recA genes have been sequenced for 25 type strains within the alpha -Proteobacteria, representing species in Rhizobium, Sinorhizobium, Mesorhizobium, Bradyrhizobium, Azorhizobium, Agrobacterium, Phyllobacterium, Mycoplana and Brevundimonas. The current genera Sinorhizobium and Mesorhizobium are well supported by these genes, each forming a distinct phylogenetic clade with unequivocal bootstrap support. There is good support for a Rhizobium clade that includes Agrobacterium tumefaciens, and the very close relationship between Agrobacterium rhizogenes and Rhizobium tropici is confirmed. There is evidence for recombination within the genera Mesorhizobium and Sinorhizobium, but the congruence of the phylogenies at higher levels indicates that the genera are genetically isolated. rRNA provides a reliable distinction between genera, but genetic relationships within a genus may be disturbed by recombination

Diagnosing nutrient limitations to lentil and chickpea in acid soils of Bangladesh

Lentil and chickpea are dietary staple crops in Bangladesh but their local production has been markedly declining in recent decades, mainly due to competition with irrigated cereals. However, in northern Bangladesh, an additional problem to their cultivation is acid surface soil conditions, potentially causing deficiencies of molybdenum (Mo) and boron (B), and toxicities of aluminium (Al), manganese (Mn) or hydrogen ion (H+). In an attempt to rehabilitate lentil and chickpea in northern Bangladesh on-farm trials were conducted to determine the response of these crops to Mo, B, and lime and Rhizobium inoculation. Despite earlier reports of widespread B deficiency in the region a response to B was only found in chickpea. Responses to Mo and Rhizobium, applied through seed priming, were found. There were responses to lime even after B, Mo, and Rhizobium had been applied, suggesting Al toxicity. Recommendations for fertilizer requirement, to fit into an overall integrated crop management package for lentil and chickpea, were modified accordingly

Response of Root Properties to Tripartite Symbiosis between Lucerne (Medicago sativa L.), Rhizobia and Mycorrhiza Under Dry Organic Farming Conditions

It is generally considered that root turnover is a major contributor to organic matter and mineral nutrient cycles in organic managed agroecosystems. Approach: This study designed to investigate whether microbial activity could affect on root properties of lucerne in an organically managed field under dry weather conditions. The trial was laid out as a factorial experiment in the fields of the University of Natural Resources and Applied Life Sciences, Vienna-Austria at Raasdorf in 2007. The experimental factors of Sinorhizobium meliloti and arbuscular mycorrhiza (AM) including Glomus etunicatum, G. intraradices and G. claroideum and irrigation levels were tested. Results: Results showed that increasing water deficit affected root dry weigh, specific root mass and root length significantly at 1% level and co-inoculation of rhizobium and mycorrhiza with irrigation could increase all root parameters. Data’s of variance analysis for mycorrhizal colonization showed that main effect of using mycorrhiza had significant effects on root parameters at 5% and 1% probability level in first and second harvest, respectively. Results of mean comparisons by Duncan’s multiple range test showed that mycorrhizal colonization was higher in the inoculated treatments by rhizobium , mycorrhiza and irrigated plots in both harvests. Double interaction of mycorrhiza and irrigation was higher in both harvests (37.05% and 65.73%, respectively). Conclusion: Hence, it can be suggested that the tripartite symbiosis of S. meliloti, AM and lucerne can improve the performance of lucerne in organic farming and under dry conditions. Such traits could be incorporated into breeding programs to improve drought tolerance especially in organic fields