Complete genome sequence of bv. viciae SRDI969, an acid-tolerant, efficient N-fixing microsymbiont of .

We report the complete genome sequence of bv. viciae SRDI969, an acid-tolerant, efficient nitrogen-fixing microorganism of . The 6.

Competition in the - symbiosis and the role of resident soil rhizobia in determining the outcomes of inoculation.

Background And Aims: Inoculation of legumes with effective N-fixing rhizobia is a common practice to improve farming profitability and sustainability. To succeed, inoculant rhizobia must overcome competition for nodulation by resident soil rhizobia that fix N ineffectively. In Kenya, where (common bean) is inoculated with highly effective CIAT899 from Colombia, response to inoculation is low, possibly due to competition from ineffective resident soil rhizobia.

Genetic diversity and symbiotic effectiveness of Phaseolus vulgaris-nodulating rhizobia in Kenya.

Phaseolus vulgaris (common bean) was introduced to Kenya several centuries ago but the rhizobia that nodulate it in the country remain poorly characterised. To address this gap in knowledge, 178 isolates recovered from the root nodules of P. vulgaris cultivated in Kenya were genotyped stepwise by the analysis of genomic DNA fingerprints, PCR-RFLP and 16S rRNA, atpD, recA and nodC gene sequences.

Sequential induction of three recombination directionality factors directs assembly of tripartite integrative and conjugative elements.

Tripartite integrative and conjugative elements (ICE3) are a novel form of ICE that exist as three separate DNA regions integrated within the genomes of Mesorhizobium spp. Prior to conjugative transfer the three ICE3 regions of M. ciceri WSM1271 ICEMcSym1271 combine and excise to form a single circular element.

Complete Genome Sequence of bv. biserrulae WSM1497, an Efficient Nitrogen-Fixing Microsymbiont of the Forage Legume .

We report here the complete genome sequence of bv. biserrulae strain WSM1497, the efficient nitrogen-fixing microsymbiont and commercial inoculant in Australia of the forage legume The genome consists of 7.2 Mb distributed across a single chromosome (6.

Evolutionary persistence of tripartite integrative and conjugative elements.

Integrative and conjugative elements (ICEs) are generally regarded as regions of contiguous DNA integrated within a bacterial genome that are capable of excision and horizontal transfer via conjugation. We recently characterized a unique group of ICEs present in Mesorhizobium spp., which exist as three entirely separate but inextricably linked chromosomal regions termed α, β and γ.

Assembly and transfer of tripartite integrative and conjugative genetic elements.

Integrative and conjugative elements (ICEs) are ubiquitous mobile genetic elements present as "genomic islands" within bacterial chromosomes. Symbiosis islands are ICEs that convert nonsymbiotic mesorhizobia into symbionts of legumes. Here we report the discovery of symbiosis ICEs that exist as three separate chromosomal regions when integrated in their hosts, but through recombination assemble as a single circular ICE for conjugative transfer.

Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the Southern African crotalarioid clade Lotononis s.l.

Background And Aims: The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.

Microvirga lupini sp. nov., Microvirga lotononidis sp. nov. and Microvirga zambiensis sp. nov. are alphaproteobacterial root-nodule bacteria that specifically nodulate and fix nitrogen with geographically and taxonomically separate legume hosts.

Strains of Gram-negative, rod-shaped, non-spore-forming bacteria were isolated from nitrogen-fixing nodules of the native legumes Listia angolensis (from Zambia) and Lupinus texensis (from Texas, USA). Phylogenetic analysis of the 16S rRNA gene showed that the novel strains belong to the genus Microvirga, with ≥ 96.1% sequence similarity with type strains of this genus.

Mesorhizobium australicum sp. nov. and Mesorhizobium opportunistum sp. nov., isolated from Biserrula pelecinus L. in Australia.

Biserrula pelecinus L. is a pasture legume that was introduced to Australia from the Mediterranean basin in 1993. Although the native rhizobial population could not nodulate B.

Root nodule bacteria isolated from South African Lotononis bainesii, L. listii and L. solitudinis are species of Methylobacterium that are unable to utilize methanol.

The South African legumes Lotononis bainesii, L. listii and L. solitudinis are specifically nodulated by highly effective, pink-pigmented bacteria that are most closely related to Methylobacterium nodulans on the basis of 16S rRNA gene homology.

The model legume Medicago truncatula A17 is poorly matched for N2 fixation with the sequenced microsymbiont Sinorhizobium meliloti 1021.

Medicago truncatula (barrel medic) A17 is currently being sequenced as a model legume, complementing the sequenced root nodule bacterial strain Sinorhizobium meliloti 1021 (Sm1021). In this study, the effectiveness of the Sm1021-M. truncatula symbiosis at fixing N(2) was evaluated.

In situ lateral transfer of symbiosis islands results in rapid evolution of diverse competitive strains of mesorhizobia suboptimal in symbiotic nitrogen fixation on the pasture legume Biserrula pelecinus L.

The multi-billion dollar asset attributed to symbiotic nitrogen fixation is often threatened by the nodulation of legumes by rhizobia that are ineffective or poorly effective in N(2) fixation. This study investigated the development of rhizobial diversity for the pasture legume Biserrula pelecinus L., 6 years after its introduction, and inoculation with Mesorhizobium ciceri bv.

Mesorhizobium ciceri biovar biserrulae, a novel biovar nodulating the pasture legume Biserrula pelecinus L.

Biserrula pelecinus L. is a pasture legume species that forms a highly specific nitrogen-fixing symbiotic interaction with a group of bacteria that belong to Mesorhizobium. These mesorhizobia have >98.

Rapid in situ evolution of nodulating strains for Biserrula pelecinus L. through lateral transfer of a symbiosis island from the original mesorhizobial inoculant.

Diverse rhizobia able to nodulate Biserrula pelecinus evolved following in situ transfer of nodA and nifH from an inoculant to soil bacteria. Transfer of these chromosomal genes and the presence of an identical integrase gene adjacent to a Phe tRNA gene in both the inoculant and recipients indicate that there was lateral transfer of a symbiosis island.

Maintenance of Intracellular pH and Acid Tolerance in Rhizobium meliloti.

The development and function of the Rhizobium meliloti-Medicago sp. symbiosis are sensitive to soil acidity. Physiological criteria that can be measured in culture which serve to predict acid tolerance in soil would be valuable.