Análisis filogenético de bacterias endosimbióticas de Genista numidica

Los rizobios son bacterias del suelo capaces de formar unas estructuras especializadas en raíces de leguminosas donde reducen dinitrógeno. Algunas de estas leguminosas, como Genista numidica Spach, juegan un importante papel ecológico y económico por la fertilización y la remediación de suelos áridos, lo que ha impulsado el estudio y la caracterización de los rizobios específicos. En la presente investigación se analizan 53 cepas de rizobios aisladas de nódulos de raíces de G. numidica de la costa de Argelia. La diversidad genética de los aislados se llevó a cabo mediante la secuenciación del gen 16S rRNA y del espacio intergénico (ITS), región situada entre los genes 16S y 23S rRNA. Los endosimbiontes de G. numidica muestran una gran diversidad filogenética. Las secuencias de los aislados mostraron proximidad a ?-proteobacterias (Bradyrhizobium sp, Sphingobium sp) y ?-proteobacterias

Phytochemical Profile and Antibacterial Activity of Retama raetam and R. sphaerocarpa cladodes from Algeria

Retama raetam (RR) and R. sphaerocarpa (RS) are shrubs growing in Algeria desert areas, where are commonly used as healing remedies because of their antiseptic, antipyretic and anti-diarrheal properties. Phytochemical studies have shown that these species are very rich in flavonoids (isoflavones) and alkaloids (quinolizidine and bipiperidyl). The aim of this study was to compare the chemical composition of both Retama species by GC/MS and LC/MS and to determinate their antimicrobial activity of two Retama species growing naturally in Algeria. Ten alkaloids and seven flavonoids were identified in cladodes of RR and RS. The quantitative analysis showed that the most abundant flavonoid of both the aqueous extract from RR and RS was the isoflavone genistein (610.0±2.8 and 408.0±14.1 mg/100 g respectively), whereas sparteine was the predominant alkaloid in RR and retamine in RS. The antibacterial activity of Retama extracts against standard strains was performed by minimum inhibitory concentration (MIC), and by the disc diffusion method (expressed by inhibition zone, IZ). Both Retama species showed the best activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA), being RS aqueous extract more active than RR aqueous extract, with MIC 125 µg/mL and bactericidal activity against both strains

Bradyrhizobium sp endosymbiont bacteria nodulate several species of spontaneous leguminous plants of Genisteae tribe from northeastern of Algeria.

218 bacterial isolates obtained from different legume species belonging to the Gensisteae tribe (Lupinus micruntus, Retama sphaerocarpa, Retama raetam and Cytisus vilosus) from different sampling sites in Algeria were studied. Cultivated on YMA medium these strains show a slow growth. The phylogenetic analysis based on 16S rDNA and the household genes of the representatives of these strains indicates that they belong to the genus Bradyrhizobium. A variety of Bradyrhizobium sp. (1, 2, 3) is present in this collection with the presence of strains that can lead to new species. (1) Boulila Farida et al., (2009). Syst. Appl. Microbiol. 32:245?255. (2) Ahnia, et al (2014). Antonie van Leeuwenhoek, J.Microbiol. ISSN 0003-6072, Volume 105 [6] 1121?1129. (3) Bourebaba and al., (2016). Syst. Appl. Microbiol. 39 266?274. This study was supported by the AECID project A1/038234/11. Bourebaba acknowledges support of the National Exceptional. Program (PNE), a fellowship from the Ministry of Higher Education and Scientific research of Algeria at CBGP, Madrid

Characterization of type VI secretion systems (T6SS) of endosymbionts from mimosa or lupine

The T6SS is a nanosyringe that injects proteins into prokaryotic or eukaryotic cells, and it is encoded in the genomes of more than 25% of Gram-negative bacteria (1). We are studying the T6SS of Rhizobium etli Mim1 and Bradyrhizobium sp. LmicA16, symbionts of Phaseolus vulgaris/Leucaena leucocephala and Lupinus micranthus/Lupinus angustifolius/Spartium junceum, respectively. R. etli Mim1 contains a T6SS gene cluster organized in two divergent operons. When the T6SS is active, Hcp, a constituent of the secretory apparatus, can be detected in the extracellular medium (2). Hcp has been immunologically detected in the supernatant of Mim1 cultures. This protein was also detected in bean nodule extracts and in cultures grown in the presence of different legumes exudates. The putative divergent promoters located between the two T6SS gene clusters were analysed by ?- gal fusions. The results showed high levels of expression of the two promoters at high OD and low values at lower ODs. Mutants affected in structural genes induced white nodules with P. vulgaris and L. leucocephala. On the other hand, mutagenesis of T6SS structural genes from LmicA16 strain produced different symbiotic phenotypes. An LmicA16 tssC mutant showed reduced levels of nitrogen fixation on L. micranthus, whereas the same mutant induced the formation of few white, non-fixing nodules on L. angustifolius and S. junceum. (1) Ho et al. (2013) Cell Host Microbe 15:9-21. (2) Wu et al. (2012) PLoS Pathog. 8:1-18 Funded by grants BIO2013-43040-P (MINECO), CGL2011-26932 (MICINN) and AL16-PID-06 (UPM)

Retama species growing in different ecological-climatic areas of northeastern Algeria have a narrow range of rhizobia that form a novel phylogenetic clade within the Bradyrhizobium genus

International audienceSixty-seven isolates were isolated from nodules collected on roots of Mediterranean shrubby legumes Retama raetam and Retama sphaerocarpa growing in seven ecological-climatic areas of northeastern Algeria. Genetic diversity of the Retama isolates was analyzed based on genotyping by restriction fragment length polymorphism of PCR-amplified fragments of the 16S rRNA gene, the intergenic spacer (IGS) region between the 16S and 23S rRNA genes (IGS), and the symbiotic genes nifH and nodC. Eleven haplotypes assigned to the Bradyrhizobium genus were identified. Significant biogeographical differentiation of the rhizobial populations was found, but one haplotype was predominant and conserved across the sites. All isolates were able to cross-nodulate the two Retama species. Accordingly, no significant genetic differentiation of the rhizobial populations was found in relation to the host species of origin. Sequence analysis of the 16S rRNA gene grouped the isolates with Bradyrhizobium elkanii, but sequence analyses of IGS, the housekeeping genes (dnaK, glnII, recA), nifH, and nodC yielded convergent results showing that the Retama nodule isolates from the northeast of Algeria formed a single evolutionary lineage, which was well differentiated from the currently named species or well-delineated unnamed genospecies of bradyrhizobia. Therefore, this study showed that the Retama species native to northeastern Algeria were associated with a specific clade of bradyrhizobia. The Retama isolates formed three sub-groups based on IGS and housekeeping gene phylogenies, which might form three sister species within a novel bradyrhizobial clad

<em>Vicia faba</em> L. in the Bejaia region of Algeria is nodulated by <em>Rhizobium leguminosarum</em> sv. <em>viciae</em>, <em>Rhizobium laguerreae</em> and two new genospecies

International audienceFifty-eight rhizobial strains were isolated from root nodules of Vicia faba cv. Equina and Vicia faba cv. Minor by the host-trapping method in soils collected from eleven sites in Bejaia, Eastern Algeria. Eleven genotypic groups were distinguished based on the combined PCR/RFLP of 16S rRNA, 16S-23S rRNA intergenic spacer and symbiotic (nodC and nodD-F) genes and further confirmed by multilocus sequence analysis (MLSA) of three housekeeping genes (recA, atpD and rpoB), the 16S rRNA gene and the nodulation genes nodC and nodD. Of the 11 genotypes, 5 were dominant and 2 were the most represented. Most of the strains shared high nodD gene sequence similarity with Rhizobium leguminosarum sv. viciae; their nodC sequences were similar to both Rhizobium leguminosarum and Rhizobium laguerreae. Sequence analyses of the 16S-23S rRNA intergenic spacer showed that all the new strains were phylogenetically related to those described from Vicia sativa and V. faba in several African, European, American and Asian countries, with which they form a group related to Rhizobium leguminosarum. Phylogenetic analysis based on MLSA of 16S rRNA, recA, atpD and rpoB genes allowed the affiliations of strain AM11R to Rhizobium leguminosarum sv. viciae and of strains EB1 and ES8 to Rhizobium laguerreae. In addition, two separate clades with Rhizobium

Phylogenetic diversity of Bradyrhizobium strains nodulating Calicotome spinosa in the Northeast of Algeria

Fifty-two slow-growing strains were isolated from root nodules of Calicotome spinosa grown in the Northeast of Algeria and grouped in 24 rep-PCR clusters. One representative strain for each profile was further phylogenetically characterized. The nearly complete 16S rRNA gene sequence indicated that all strains were affiliated to Bradyrhizobium. Multi-Locus Sequence Analysis (MLSA) of the atpD, glnII and recA genes and of the 16S-23S rRNA internal transcribed spacer (ITS) showed that these strains formed four divergent clusters: one close to Bradyrhizobium canariense and Bradyrhizobium lupini and three others separate from all the described species, representing three putative new Bradyrhizobium species. A phylogenetic analysis based on the nodC gene sequence affiliated the strains to either of the two symbiovars, genistearum or retamae

Bradyrhizobium sp endosymbiont bacteria nodulate several species of spontaneous leguminous plants of Genisteae tribe from northeastern of Algeria.

218 bacterial isolates obtained from different legume species belonging to the Gensisteae tribe (Lupinus micruntus, Retama sphaerocarpa, Retama raetam and Cytisus vilosus) from different sampling sites in Algeria were studied. Cultivated on YMA medium these strains show a slow growth. The phylogenetic analysis based on 16S rDNA and the household genes of the representatives of these strains indicates that they belong to the genus Bradyrhizobium. A variety of Bradyrhizobium sp. (1, 2, 3) is present in this collection with the presence of strains that can lead to new species. (1) Boulila Farida et al., (2009). Syst. Appl. Microbiol. 32:245?255. (2) Ahnia, et al (2014). Antonie van Leeuwenhoek, J.Microbiol. ISSN 0003-6072, Volume 105 [6] 1121?1129. (3) Bourebaba and al., (2016). Syst. Appl. Microbiol. 39 266?274. This study was supported by the AECID project A1/038234/11. Bourebaba acknowledges support of the National Exceptional. Program (PNE), a fellowship from the Ministry of Higher Education and Scientific research of Algeria at CBGP, Madrid

Characterization of type VI secretion systems (T6SS) of endosymbionts from mimosa or lupine

The T6SS is a nanosyringe that injects proteins into prokaryotic or eukaryotic cells, and it is encoded in the genomes of more than 25% of Gram-negative bacteria (1). We are studying the T6SS of Rhizobium etli Mim1 and Bradyrhizobium sp. LmicA16, symbionts of Phaseolus vulgaris/Leucaena leucocephala and Lupinus micranthus/Lupinus angustifolius/Spartium junceum, respectively. R. etli Mim1 contains a T6SS gene cluster organized in two divergent operons. When the T6SS is active, Hcp, a constituent of the secretory apparatus, can be detected in the extracellular medium (2). Hcp has been immunologically detected in the supernatant of Mim1 cultures. This protein was also detected in bean nodule extracts and in cultures grown in the presence of different legumes exudates. The putative divergent promoters located between the two T6SS gene clusters were analysed by ?- gal fusions. The results showed high levels of expression of the two promoters at high OD and low values at lower ODs. Mutants affected in structural genes induced white nodules with P. vulgaris and L. leucocephala. On the other hand, mutagenesis of T6SS structural genes from LmicA16 strain produced different symbiotic phenotypes. An LmicA16 tssC mutant showed reduced levels of nitrogen fixation on L. micranthus, whereas the same mutant induced the formation of few white, non-fixing nodules on L. angustifolius and S. junceum. (1) Ho et al. (2013) Cell Host Microbe 15:9-21. (2) Wu et al. (2012) PLoS Pathog. 8:1-18 Funded by grants BIO2013-43040-P (MINECO), CGL2011-26932 (MICINN) and AL16-PID-06 (UPM)