Structural Polymorphism of <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> Genes Related to Virulence and Salt Tolerance

Analysis of the structural polymorphism of eight genes in Sinorhizobium meliloti (nodA, nodB, nodC, and nodH, as well as betA, betB, betC, and betB2) involved in virulence control and salt tolerance, respectively, was carried out in native populations from two geographically distant areas of alfalfa diversity. These areas are located in the North Caucasian gene center of cultivated plants (NCG) and in the modern center of introgressive hybridization of alfalfa located next to the Aral Sea area (PAG) subjected to salinization. RFLP types (alleles) of the nod and bet genes, similar to those in the reference strain Rm1021 (A-type) and different from them (divergent, or D-type alleles) were revealed. The combinations for A- and D-type alleles of the aforementioned genes (analysis of the linkage disequilibrium, LD) were studied in both populations. It was shown that D-type alleles of the nod genes were two times more frequent in the NCG population, while D-type alleles of the bet genes were predominantly identified in the PAG population. At the same time, different combinations of D-type alleles of both the nod and bet genes prevailed in populations. For instance, in the case of the glycine betaine metabolism pathway, these were the betC and betB2 genes in NCG population and betB and betA genes in PAG population. The state of linkage disequilibrium was shown for 60.7% of combinations of alleles of the nod and bet genes in the S. meliloti strains from NCG and more than twice less in strains from the PAG population. It was concluded that clonal lines prevailed in NCG, while the PAG population of S. meliloti had a panmictic structure with revealed single clonal lines.     

The diversity of rhizobia nodulating the <Emphasis Type="Italic">Medicago</Emphasis>, <Emphasis Type="Italic">Melilotus</Emphasis> and <Emphasis Type="Italic">Trigonella</Emphasis> inoculation group in Egypt is marked by the dominance of two genetic types

Twenty four rhizobial strains were isolated from root nodules of Melilotus, Medicago and Trigonella plants growing wild in soils throughout Egypt. The nearly complete 16S rRNA gene sequence from each strain showed that 12 strains (50 %) were closely related to the Ensifer meliloti LMG6133^T type strain with identity values higher than 99.0 %, that 9 (37.5 %) strains were more than 99 % identical to the E. medicae WSM419^T type strain, and that 3 (12.5 %) strains showed 100 % identity with the type strain of N. huautlense S02^T. Accordingly, the diversity of rhizobial strains nodulating wild Melilotus, Medicago and Trigonella species in Egypt is marked by predominance of two genetic types, E. meliloti and E. medicae, although the frequency of isolation was slightly higher in E. meliloti. Sequencing of the symbiotic nodC gene from selected Medicago and Melilotus strains revealed that they were all similar to those of the E. meliloti LMG6133^T and E. medicae WSM419^T type strains, respectively. Similarly, nodC sequences of strains identified as members of the genus Neorhizobium were more than 99 % identical to that of N. galegae symbiovar officinalis HAMBI 114.     

Morphological and genetic variability in small island populations of the striped field mouse <Emphasis Type="Italic">Apodemus agrarius</Emphasis> Pallas, 1771

Morphological (craniometrical characteristics and variations of cusp t3 on the second upper molar (M²)) and genetic (polymorphism of chromosomes and blood proteins) variability was analyzed in small island populations of the striped field mouse Apodemus agrarius Pallas, 1771 from the Peter the Great Bay (Sea of Japan). It was found that the absence of t3 on M² is not a specific trait for A. agrarius. It was demonstrated that the population of field mice on the Bolshoy Pelis Island significantly differs from the populations from other islands and from the mainland according to the craniometrical parameters, teeth phenes, and variants of blood transferrin. The possible age of establishment of the island populations of the striped field mouse is discussed.     

Characterization of surface motility in <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis>: regulation and role in symbiosis

Sinorhizobium meliloti can exhibit diverse modes of surface translocation whose manifestation depends on the strain. The mechanisms involved and the role played by the different modes of surface motility in the establishment of symbiosis are largely unknown. In this work, we have characterized the surface motility shown by two S. meliloti reference strains (Rm1021 and GR4) under more permissive conditions for surface spreading and analyzed the symbiotic properties of two flagella-less S. meliloti mutants with different behavior on surfaces. The use of Noble agar in semisolid minimal medium induces surface motility in GR4, a strain described so far as non-motile on surfaces. The motility exhibited by GR4 is swarming as revealed by the non-motile phenotype of the flagella-less flaAB mutant. Intriguingly, a flgK mutation which also abolishes flagella production, triggers surface translocation in GR4 through an as yet unknown mechanism. In contrast to GR4, Rm1021 moves over surfaces using mostly a flagella-independent motility which is highly reliant on siderophore rhizobactin 1021 production. Surprisingly, this motility is absent in a flagella-less flgE mutant. In addition, we found that fadD loss-of-function, known to promote surface motility in S. meliloti, exerts different effects on the two reference strains: while fadD inactivation promotes a flagella-independent type of motility in GR4, the same mutation interferes with the surface translocation exhibited by the Rm1021 flaAB mutant. The symbiotic phenotypes shown by GR4flaAB and GR4flgK, non-flagellated mutants with opposite surface motility behavior, demonstrate that flagella-dependent motility positively influences competitiveness for nodule occupation, but is not crucial for optimal infectivity.     

Molecular and morphological characterization of the predatory mite <Emphasis Type="Italic">Amblyseius largoensis</Emphasis> (Acari: Phytoseiidae): surprising similarity between an Asian and American populations

The accurate characterization of biological control agents is a key step in control programs. Recently, Amblyseius largoensis from Thailand were introduced in Brazil to evaluate their efficiency for the control of the red palm mite, Raoiella indica. The aim of this study was to confirm their identification and to characterize the population from Thailand, comparing it to populations of the Americas and Indian Ocean islands. In addition, a population of A. largoensis from New Caledonia, Oceania, of which DNA sequences were available, was included in phylogenetic analyses. Morphometric data obtained for the population of A. largoensis from Thailand were compared to those of populations from Reunion Island and the Americas through univariate and multivariate analyses. Two DNA fragments were amplified and sequenced: the nuclear ribosomal region ITSS and the mitochondrial 12S rRNA. Haplotypes (12S rRNA) and genotypes (ITSS) were identified and phylogenetic analyses using both fragments were conducted separately and combined using maximum likelihood and the Bayesian information criterion. The integrative approach reveals morphometric and molecular variabilities among populations of A. largoensis and shows that the population identified as A. largoensis collected in Thailand, as well as that from New Caledonia, are conspecific to the populations of the Americas and Indian Ocean islands. Populations from the Americas and Asia are more related to each other than with that from the Indian Ocean islands. Hypotheses to explain this clustering are proposed. Data on the molecular intraspecific variability of this predatory mite from remote areas will be helpful for the development of molecular diagnosis.     

Song frequency correlates with latitude and individual body size in the cicada <Emphasis Type="Italic">Mogannia formosana</Emphasis> Matsumura (Hemiptera: Cicadidae)

Analyses of acoustic variation between and within populations can help to clarify the evolution and diversification of cicada calling songs. In this study, we analyzed the acoustic variation in the calling song of Mogannia formosana within Taiwan and between Taiwan and Green Island to assess the effects of geographic locations. Furthermore, chorusing males in the Green Island population were recorded and collected from the same habitat site during the same time period to investigate the relationship between individual body size and the acoustic features of calling songs. Among populations of M. formosana, we found that most of the acoustic variation in M. formosana calling songs was associated with frequency parameters, in which six frequency parameters changed significantly with latitude on the island of Taiwan. In contrast, temporal parameters, which were associated with principal components corresponding to less acoustic variation than that of the first principal component, were also found to be significant among populations but did not show consistent trends of difference with latitude. However, the geographically isolated Green Island population exhibited the lowest number of short echemes in segment B, which is the diagnostic structure employed to separate M. formosana from other M. species. This finding suggests that the temporal pattern of segment B in the calling songs of M. formosana might be important for both population differentiation and interspecific recognition. In a chorus of the Green Island population, the sound frequency of the last short echeme was found to be significantly correlated with individual body size. The possible role played by sexual selection in shaping sound frequency as a result of its reliable association with body size was discussed. We suggest that, in comparison with temporal elements, the frequency elements of segment B in calling songs of M. formosana in chorus can serve as a more reliable indicator of body size for female mate choice.     

Conservation genetics of the highly endangered Azorean endemics <Emphasis Type="Italic">Euphrasia azorica</Emphasis> and <Emphasis Type="Italic">Euphrasia grandiflora</Emphasis> using new SSR data

In the Azores Islands, two Euphrasia L. (Orobanchaceae) endemic species are recognized: Euphrasia azorica H.C.Watson, an annual herb, in Flores and Corvo, and Euphrasia grandiflora Hochst. ex Seub., a semi-shrub, in Pico, São Jorge and Terceira. Both species are highly endangered and protected by the Bern Convention and Habitats Directive. A population genetics study was conducted with new microsatellite primer pairs in 159 individuals of E. azorica and E. grandifolia, sampled from populations in Flores, Corvo, Pico and São Jorge. Allele sizing suggested that E. azorica is a diploid while E. grandiflora is a tetraploid. Euphrasia grandiflora revealed higher genetic diversity then E. azorica. The E. grandiflora population of Morro Pelado in São Jorge, displayed higher genetic diversity when compared with all others, while the E. azorica population of Madeira Seca in Corvo, showed the lowest. Private and less common bands were also overall higher in E. grandiflora populations. Population genetic structure analysis confirmed a distinctiveness between the two Azorean endemic Euphrasia, in addition to island-specific genetic patterns in E. azorica. The genetic structure obtained for E. grandiflora was complex with the populations of Cabeço do Mistério in Pico Island and of Pico da Esperança in São Jorge sharing the same genetic group, while a putative spatial barrier to gene flow was still retrieved between both islands. Although some populations of both species might benefit from propagation actions, studies are needed on plant host species and translocations between islands or between some populations of a same island should be avoided, due to the occurrence of putative ESUs. Eradication of invasive species and control of grazing will be fundamental to promote in situ restauration.     

Diversity and symbiotic divergence of endophytic and non-endophytic rhizobia of <Emphasis Type="Italic">Medicago sativa</Emphasis>

Knowledge of rhizobium diversity is helping to enable the utilization of rhizobial resources. To analyze the phenotypic and genetic diversity and the symbiotic divergence of rhizobia of Medicago sativa, 30 endophytic and non-endophytic isolates were collected from different parts of five alfalfa varieties in three geographic locations in Gansu, China. Numerical analyses based on 72 phenotypic properties and restriction fragment length polymorphism (RFLP) fingerprinting indicated the abundant phenotypic and genetic diversity of the tested strains. According to the phylogenetic analysis of 16S RNA, atpD, glnII, and recA gene sequences, Rhizobium and Ensifer were further classified into four different genotypes: Rhizobium radiobacter, Rhizobium sp., Rhizobium rosettiformans, and Ensifer meliloti. The differences in architecture and functioning of the rhizobial genomes and, to a lesser extent, environment diversification helped explain the diversity of tested strains. The tested strains exhibited similar symbiotic feature when inoculated onto M. sativa cvs. Gannong Nos. 3 and 9 and Qingshui plants for the clustering feature of their parameter values. An obvious symbiotic divergence of rhizobial strains was observed in M. sativa cvs. Longzhong and WL168HQ plants because of the scattered parameter values. Their symbiotic divergence differed according to alfalfa varieties, which indicated that the sensitivity of different alfalfa varieties to rhizobial strains may differ. Most of the tested strains exhibited plant growth-promoting traits including phosphate solubilization and production of indole-3-acetic acid (IAA) when colonizing plant tissues and soil.     

Development and characterization of 12 polymorphic microsatellite loci in the sea sandwort, <Emphasis Type="Italic">Honckenya peploides</Emphasis>

Codominant marker systems are better suited to analyze population structure and assess the source of an individual in admixture analyses. Currently, there is no codominant marker system using microsatellites developed for the sea sandwort, Honckenya peploides (L.) Ehrh., an early colonizer in island systems. We developed and characterized novel microsatellite loci from H. peploides, using reads collected from whole genome shotgun sequencing on a 454 platform. The combined output from two shotgun runs yielded a total of 62,669 reads, from which 58 loci were screened. We identified 12 polymorphic loci that amplified reliably and exhibited disomic inheritance. Microsatellite data were collected and characterized for the 12 polymorphic loci in two Alaskan populations of H. peploides: Fossil Beach, Kodiak Island (n?=?32) and Egg Bay, Atka Island (n?=?29). The Atka population exhibited a slightly higher average number of alleles (3.9) and observed heterozygosity (0.483) than the Kodiak population (3.3 and 0.347, respectively). The overall probability of identity values for both populations was PID?=?2.892e^?6 and PID_sib?=?3.361e^?3. We also screened the 12 polymorphic loci in Wilhelmsia physodes (Fisch. ex Ser.) McNeill, the most closely related species to H. peploides, and only one locus was polymorphic. These microsatellite markers will allow future investigations into population genetic and colonization patterns of the beach dune ruderal H. peploides on new and recently disturbed islands.     

Genetic polymorphism of commander islands polar foxes <Emphasis Type="Italic">Alopex lagopus semenovi</Emphasis> Ognev, 1931 and <Emphasis Type="Italic">Alopex lagopus beringiensis</Emphasis> Merriam, 1902

The polymorphism of the mitochondrial DNA (mtDNA) control region sequence was examined in 30 polar foxes from Bering Island and 30 polar foxes from Mednyi Island. Seven haplotypes were revealed in polar foxes from Bering Island, and one, in polar foxes from Mednyi Island. The age of divergence of these populations (12 000 ± 6 000 years) was calculated based on a fragment of the D-loop. In Bering polar foxes, the sequence nucleotide diversity (π) was 0.003 (S.D. = 0.002), the haplotype diversity h in Bering polar foxes was 0.835 (S.D. = 0.037). The effective number of females n the Bering Island population was estimated as 105 animals.     

A nodule endophytic plant growth-promoting <Emphasis Type="Italic">Pseudomonas</Emphasis> and its effects on growth,nodulation and metal uptake in <Emphasis Type="Italic">Medicago lupulina</Emphasis> under copper stress

The aim of this study was to determine the plant growth-promoting potential of the nodule endophytic Pseudomonas brassicacearum strain Zy-2-1 when used as a co-inoculant of Medicago lupulina with Sinorhizobium meliloti under copper (Cu) stress conditions. Strain Zy-2-1 was capable of producing ACC deaminase activity, IAA and siderophores, and was able to grow in the presence of Cu²⁺ up to 2.0 mmol/L. Co-inoculation of S. meliloti with Zy-2-1 enhanced M. lupulina root fresh weight, total plant dry weight, number of nodules, nodule fresh weight and nitrogen content in the presence of 100 or 300 mg/kg Cu²⁺. In the presence of 500 mg/kg Cu²⁺, co-inoculation with S. meliloti and strain Zy-2-1 increased plant height, number of nodules, nodule fresh weight and nitrogen content in comparison to S. meliloti inoculation alone. Furthermore, a higher amount of Cu accumulation in both shoots and roots and a higher level of Cu translocation to shoots were observed in co-inoculated plants. These results demonstrate that co-inoculation of M. lupulina with S. meliloti and P. brassicacearum Zy-2-1 improves plant growth, nitrogen nutrition and metal extraction potential. This can be of practical importance in the remediation of heavy metal-contaminated soils.     

千岛湖社鼠种群遗传现状及与生境面积的关系

以千岛湖地区13个岛屿上的社鼠(Niviventer confucianus)种群为研究对象,利用13个微卫星位点分析了13个社鼠种群的遗传现状,并探讨了种群遗传现状与岛屿面积大小之间的关系。研究结果显示,13个社鼠种群的平均观测等位基因数(Na)与平均有效等位基因数(Ne)分别为7.385,5.952,平均期望杂合度(He)与平均观测杂合度(Ho)分别为0.819,0.930,平均多态信息含量(PIC)为0.760,说明13个社鼠种群均具有较高的遗传多样性。13个种群间的分化系数(Fst)为0.053,表明种群间的遗传分化较小。3个面积较大且相近岛屿上社鼠种群,即高仙阁种群 (Gaoxiange Island,G);乌石T岛种群 (Wushi T Island,WT);东门岛种群 (Dongmen Island,DM)间的Fst值均小于0.05,表明种群间无分化,而小岛种群与大岛种群间的分化却比较明显。此外,一元回归结果显示,多态信息含量(PIC)和Shannon多样性指数(I)与岛屿面积大小之间均存在显著地正相关关系。以上结果说明,在社鼠种群进化过程中,生境面积的缩小可能使种群的遗传结构发生改变,并有可能导致种群的快速进化。     

Long-term effects of feral goats (<Emphasis Type="Italic">Capra hircus</Emphasis>) on Mediterranean island communities: results from whole island manipulations

Islands exhibit disproportionally high biodiversity, however high levels of endemism and simplified food webs make their communities susceptible to invasive species. Introduced goats (Capra hircus), a generalist herbivore, are among the most harmful invasive species on islands. Concern about goat impacts on island communities have resulted in eradication programs, which have been generally implemented without comprehensive evaluation and monitoring. Unintended consequences may follow eradication, as grazing can have complex effects on island food webs. Using whole island manipulations, we evaluate the long-term, community-wide effects of goat herbivory, as well as their subsequent removal, in a system of 16 islands in the Aegean Sea (Greece) located within the Mediterranean biodiversity hotspot. Goat grazing on these islands is a major conservation concern, as these support endemic plant communities that have evolved in low herbivory conditions and lack appropriate defenses. We show that goat introductions lead to significant decreases in vegetation height, percent cover, and biomass but not to immediate plant species loss, as native island endemics are replaced with widespread generalist taxa carried in by the livestock. Additionally, goats contribute to the desertification of islands by initiating a long-term soil loss cycle that continues even after goats are removed; however, remaining soil structure and chemistry are not affected. Island arthropod populations do not appear to be significantly impacted by goat introduction or removal, except for a distinct increase in the order Diptera with goat presence. This study also reaffirms the role of seabirds in providing important marine subsidies, rich in nitrogen and phosphorus, to island food webs. Plant species diversity declines following goat removal, and vegetation cover returns only partially, as further recovery is being prevented by the long-term loss of soil. This suggests that following goat removal, island communities may require additional restoration efforts, including seabird reestablishment and reintroduction of extirpated plant populations, to promote island recovery.     

Contrasting post-settlement selection results in many-to-one mapping of high performance phenotypes in the Hawaiian waterfall-climbing goby <Emphasis Type="Italic">Sicyopterus stimpsoni</Emphasis>

Natural selection drives adaptive evolution, but contrasting environmental pressures may lead to trade-offs between phenotypes that confer different performances. Such trade-offs may weaken the strength of selection and/or generate complex fitness surfaces with multiple local optima that correspond to different selection regimes. We evaluated how differences in patterns of phenotypic selection might promote morphological differences between subpopulations of the amphidromous Hawaiian waterfall-climbing goby, Sicyopterus stimpsoni. We conducted laboratory experiments on fish from the islands of Kaua‘i and Hawai‘i (the “Big Island”) to compare patterns of linear and nonlinear selection, and the opportunity for selection, that result from two contrasting pressures, predator evasion and waterfall climbing, which vary in intensity between islands. We found directional and nonlinear selection were strongest when individuals were exposed to their primary selective pressures (predator evasion on Kaua‘i, waterfall climbing on the Big Island). However, the opportunity for selection was greater for the non-primary pressure: climbing on Kaua‘i, predator evasion on the Big Island. Canonical rotation of the nonlinear gamma matrix demonstrated that individuals from Kaua‘i and the Big Island occupy regions near their local fitness peaks for some traits. Therefore, selection for predator evasion on Kaua‘i and climbing on the Big Island may be less effective in promoting morphological changes in this species, because variation of functionally important traits in their respective environments may have been reduced by directional or stabilizing selection. These results demonstrate that despite constraints on the opportunities for selection, population differences in phenotypic traits can arise due to differences in selective regimes. For S. stimpsoni, sufficient variation exists in other locomotor traits, allowing for necessary levels of performance in the contrasting selective regime (i.e., climbing on Kaua‘i and predator evasion on the Big Island) through many-to-one-mapping, which may be essential for the survival of local populations in an evanescent island environment.     

Hydrogenogenic and sulfidogenic growth of <Emphasis Type="Italic">Thermococcus</Emphasis> archaea on carbon monoxide and formate

Enrichment and pure cultures of hyperthermophilic archaea capable of anaerobic growth on one-carbon compounds (CO and/or formate) were obtained from deep-sea sites of hydrothermal activity at the Mid-Atlantic Ridge, Lau Basin, and Guaymas Basin. All isolates belonged to the T. barophilus?T. paralvinellae group within the genus Thermococcus. In all cases available for analysis, the genomes of Thermococcus strains capable of growth by hydrogenogenic utilization of CO and/or formate contained clusters of genes encoding energy-converting hydrogenase and either CO dehydrogenase or formate dehydrogenase and formate transporter. Apart from the previously known processes of hydrogenogenic oxidation of CO and formate, the oxidation of these substrates coupled to sulfur reduction was observed, processes previously unknown among archaea. The capacities for hydrogenogenic or sulfidogenic oxidation of CO and formate occurred in the studied strains in all possible combinations, which could only in part be explained by peculiarities of organization of genetic determinants revealed in the genomes. Investigation of CO and formate consumption kinetics revealed that T. barophilus strain Ch5 was able to grow at concentrations close to the environmental ones. Thus, it was shown that hyperthermophilic archaea from deep-sea hydrothermal vents are able to utilize one-carbon substrates of abiotic origin both in the presence of an electron acceptor (sulfur) and in its absence. These processes were probably of importance under the conditions of the early Earth biosphere.     

Pathogenicity and genomic characterization of <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> strain PB1937 causing shrimp acute hepatopancreatic necrosis disease in China

Acute hepatopancreatic necrosis disease (AHPND) outbreaks in cultured shrimps were identified in Zhangpu, China. One Vibrio parahaemolyticus strain PB1937 was isolated from the cultured shrimps and was confirmed as a causative agent of the AHPND outbreak by employing Koch’s four postulates. Challenge tests with 10⁶ cells ml^?1 of strain PB1937 caused 100% mortality of shrimps, indicating it had sufficient virulence to cause the outbreak. Phylogenomic analysis revealed a clear divergence between PB1937 and 14 publicly available V. parahaemolyticus strains and divided 11 AHPND-causing strains into six genomic clusters. Prophage profiling of above strains revealed strong correlations with their genomic relationship, while Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) were almost absent in the genomes. The binary toxin gene pirAB^vp directly related to the development of AHPND was found in a 70-kb plasmid p1937-1 in PB1937 but was absent in a 78-kb novel plasmid p1937-2, which shared 46% sequence similarity with p1937-1. Comparative genomic analysis revealed that PB1937 has a novel truncated type VI secretion system (T6SS1) which possibly affects its antibacterial activity. In addition, three novel genomic islands were reported. The analysis of the genomes gave some clues regarding the correlation of virulence with its genomic trait for the AHPND strains.     

Evidence of the island rule and microevolution in white-footed mice (<Emphasis Type="Italic">Peromyscus leucopus</Emphasis>) in an urban harbor archipelago

The island rule generally states that larger species are dwarfed on islands while smaller species exhibit gigantism. Among the smaller species in which this pattern has been observed, rodents have been a focus of numerous studies. Through our long-term trapping on the Boston Harbor Islands, USA, we have revealed that the white-footed mice on Bumpkin and Peddocks Islands exhibit a significantly larger body size than their mainland counterparts. On Bumpkin Island, adult mice averaged 28.2 g (n = 187, SE ± 0.35) and on Peddocks Island adult animals averaged 31.2 g (n = 85, SE ± 0.42). Published average masses for this species range from 15 to 25 g for adults. Additionally, the mice on Bumpkin Island have shown an increase in mass over the course of our study and this increase was significant between 2011 and 2014 when no trapping occurred on that island. The large size suggests that these animals have been isolated on these islands for a sufficient amount of time for divergence to occur. Additionally, the changes in mass over time, in a population with annual turnover, suggests that microevolution in response to environmental factors may be taking place.     

Alkalinity of Lanzarote soils is a factor shaping rhizobial populations with Sinorhizobium meliloti being the predominant microsymbiont of Lotus lancerottensis

Lotus lancerottensis is an endemic species that grows widely throughout Lanzarote Island (Canary Is.). Characterization of 48 strains isolated from root nodules of plants growing in soils from eleven locations on the island showed that 38 isolates (79.1%) belonged to the species Sinorhizobium meliloti, whereas only six belonged to Mesorhizobium sp., the more common microsymbionts for the Lotus. Other genotypes containing only one isolate were classified as Pararhizobium sp., Sinorhizobium sp., Phyllobacterium sp. and Bradyrhizobium-like. Strains of S. meliloti were distributed along the island and, in most of the localities they were exclusive or major microsymbionts of L. lancerottensis. Phylogeny of the nodulation nodC gene placed the S. meliloti strains within symbiovar lancerottense and the mesorhizobial strains with the symbiovar loti. Although strains from both symbiovars produced effective N₂-fixing nodules, S. meliloti symbiovar lancerottense was clearly the predominant microsymbiont of L. lancerottensis. This fact correlated with the better adaptation of strains of this species to the alkaline soils of Lanzarote, as in vitro characterization showed that while the mesorhizobial strains were inhibited by alkaline pH, S. meliloti strains grew well at pH 9.     

Genomic Islands in <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> Rm1021, Nitrogen-Fixing Symbiont of Alfalfa

In silico analysis of open reading frames of genomic islands of Sinorhizobium meliloti Rm1021 was performed. This strain is a typical representative of soil bacteria forming nitrogen-fixing symbiosis with legume host plants from the alfalfa cross-inoculation group. It was demonstrated that genomic islands had mosaic structure, in which blocks of functional genes, IS-elements and noncoding RNA alternated. Genomic islands contained as well the components of T4SS and T4CP systems, and lacked systems of conjugative mobilization of islands. It was concluded that two of the three islands could be the variants of reduced integrative conjugative elements, and the third island represented a reduced integrated conjugative transposon. Site-specific integration of islands occurred into a 15–31 bp sequence (depending on the island) localized at the 3′-end of the tRNA gene, which is then shifted rightward, while the remaining part of the tRNA gene is completed by a similar sequence that exists in the island. A suggestion on the existence of “speciesspecific insertion hotspots” for genomic islands of root nodule bacteria was put forward.