RESUMEN
In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima < M. truncatula < M. marina < L. sativus < L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.
Asunto(s)
Cadmio/toxicidad , Fabaceae/fisiología , Rhizobium/fisiología , Sinorhizobium/fisiología , Biodegradación Ambiental , ADN Bacteriano/genética , ADN Ribosómico/genética , Fabaceae/efectos de los fármacos , Fabaceae/microbiología , Variación Genética , Genotipo , Lathyrus/efectos de los fármacos , Lathyrus/microbiología , Lathyrus/fisiología , Lens (Planta)/efectos de los fármacos , Lens (Planta)/microbiología , Lens (Planta)/fisiología , Medicago/efectos de los fármacos , Medicago/microbiología , Medicago/fisiología , Fenotipo , Filogenia , Nodulación de la Raíz de la Planta/efectos de los fármacos , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , ARN Ribosómico 16S/genética , Rhizobium/clasificación , Rhizobium/genética , Rhizobium/aislamiento & purificación , Nódulos de las Raíces de las Plantas/microbiología , Nódulos de las Raíces de las Plantas/fisiología , Sinorhizobium/clasificación , Sinorhizobium/genética , Sinorhizobium/aislamiento & purificación , Suelo/química , Simbiosis/efectos de los fármacos , TúnezRESUMEN
A collection of rhizobia isolated from Acacia tortilis subsp. raddiana nodules from various arid soils in Tunisia was analyzed for their diversity at both taxonomic and symbiotic levels. The isolates were found to be phenotypically diverse. The majority of the isolates tolerated 3% NaCl and grew at 40 °C. Genetic characterization emphasized that most of the strains (42/50) belong to the genus Ensifer, particularly the species Ensifer meliloti, Ensifer garamanticus, and Ensifer numidicus. Symbiotic properties of isolates showed diversity in their capacity to nodulate their host plant and to fix atmospheric nitrogen. The most effective isolates were closely related to E. garamanticus. Nodulation tests showed that 3 strains belonging to Mesorhizobium genus failed to renodulate their host plant, which is surprising for symbiotic rhizobia. Furthermore, our results support the presence of non-nodulating endophytic bacteria belonging to the Acinetobacter genus in legume nodules.
Asunto(s)
Acacia/microbiología , Rhizobium/clasificación , Sinorhizobium meliloti/clasificación , Microbiología del Suelo , Simbiosis , Filogenia , Rhizobium/genética , Rhizobium/aislamiento & purificación , Rhizobium/fisiología , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/aislamiento & purificación , Sinorhizobium meliloti/fisiología , Suelo/química , TúnezRESUMEN
Diversity of 50 bacterial isolates recovered from root nodules of Prosopis farcta grown in different arid soils in Tunisia, was investigated. Characterization of isolates was assessed using a polyphasic approach including phenotypic characteristics, 16S rRNA gene PCR--RFLP and sequencing, nodA gene sequencing and MLSA. It was found that most of isolates are tolerant to high temperature (40°C) and salinity (3%). Genetic characterization emphasizes that isolates were assigned to the genus Ensifer (80%), Mesorhizobium (4%) and non-nodulating endophytic bacteria (16%). Forty isolates belonging to the genus Ensifer were affiliated to Ensifer meliloti, Ensifer xinjiangense/Ensifer fredii and Ensifer numidicus species. Two isolates belonged to the genus Mesorhizobium. Eight isolates failing to renodulate their host plant were endophytic bacteria and belonged to Bacillus, Paenibacillus and Acinetobacter genera. Symbiotic properties of nodulating isolates showed a diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Isolate PG29 identified as Ensifer meliloti was the most effective one. Ability of Prosopis farcta to establish symbiosis with rhizobial species confers an important advantage for this species to be used in reforestation programs. This study offered the first systematic information about the diversity of microsymbionts nodulating Prosopis farcta in the arid regions of Tunisia.
Asunto(s)
Alphaproteobacteria/clasificación , Alphaproteobacteria/aislamiento & purificación , Prosopis/microbiología , Rhizobiaceae/clasificación , Rhizobiaceae/aislamiento & purificación , Nódulos de las Raíces de las Plantas/microbiología , Aciltransferasas/genética , Alphaproteobacteria/genética , Proteínas Bacterianas/genética , ADN Bacteriano/genética , Clima Desértico , Genes de ARNr , Filogenia , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , ARN Ribosómico 16S/genética , Rhizobiaceae/genética , Simbiosis , TúnezRESUMEN
Nine isolates from Argyrolobium uniflorum, Lotus creticus , Medicago sativa (Tunisia) and Lotus arabicus (Senegal) were analysed by multilocus sequence analysis (MLSA) of five housekeeping genes (recA, atpD, glnA, gltA and thrC), the 16S rRNA gene and the nodulation gene nodA. Analysis of the individual and concatenated gene sequences demonstrated that the nine new strains constituted three stable, well-supported (bootstrap and gene sequence similarity values) monophyletic clusters, A, B and C, all belonging to the branch of the genus Ensifer, regardless of the phylogenetic reconstruction method used (maximum likelihood, maximum-parsimony, neighbour-joining). The three groups were further characterized by API 100 auxanographic tests, host specificity and nodA gene sequence analysis. On the basis of these data, clusters A and C are suggested as representing two novel species within the genus Ensifer, for which the names Ensifer numidicus sp. nov. (type strain ORS 1407(T)=LMG 24690(T)=CIP 109850(T)) and Ensifer garamanticus sp. nov. (type strain ORS 1400(T)=LMG 24692(T)=CIP 109916(T)) are proposed. The cluster B strains were assigned to Ensifer adhaerens genomovar A.
Asunto(s)
Fabaceae/microbiología , Lotus/microbiología , Medicago/microbiología , Rhizobiaceae/clasificación , Rhizobiaceae/genética , Nódulos de las Raíces de las Plantas/microbiología , Proteínas Bacterianas/genética , Técnicas de Tipificación Bacteriana , ADN Bacteriano/genética , ADN Ribosómico/genética , Datos de Secuencia Molecular , Filogenia , ARN Ribosómico 16S/genética , Rhizobiaceae/aislamiento & purificación , Rhizobiaceae/metabolismo , Análisis de Secuencia de ADNRESUMEN
Forty-two bacterial isolates from root nodules of Argyrolobium uniflorum growing in the arid areas of Tunisia were characterized by phenotypic features, RFLP, and sequencing of PCR-amplified 16S rRNA genes. The isolates were found to be phenotypically diverse. The majority of the isolates tolerated 3% NaCl and grew at temperatures up to 40 degrees C. Phylogenetically, the new isolates were grouped in the genera Sinorhizobium (27), Rhizobium (13), and Agrobacterium (2). Except for the 2 Agrobacterium isolates, all strains induced nodulation on Argyrolobium uniflorum, but the number of nodules and nitrogen fixation efficiency varied among them. Sinorhizobium sp. strains STM 4034, STM 4036, and STM 4039, forming the most effective symbiosis, are potential candidates for inoculants in revegetalisation programs.
Asunto(s)
Fabaceae/microbiología , Raíces de Plantas/microbiología , Rhizobium/clasificación , Rhizobium/aislamiento & purificación , Sinorhizobium/clasificación , Sinorhizobium/aislamiento & purificación , Antibacterianos/farmacología , Dermatoglifia del ADN , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Genes de ARNr , Datos de Secuencia Molecular , Fijación del Nitrógeno , Filogenia , Polimorfismo de Longitud del Fragmento de Restricción , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Rhizobium/genética , Rhizobium/fisiología , Solución Salina Hipertónica/farmacología , Análisis de Secuencia de ADN , Homología de Secuencia de Ácido Nucleico , Sinorhizobium/genética , Sinorhizobium/fisiología , Simbiosis , Temperatura , TúnezRESUMEN
AIMS: Genista saharae, indigenous of Sahara, is a spontaneous shrub that plays an important ecological role for the preservation and fertility of poor and eroded soils. This legume has not been examined for its root nodule bacteria. The taxonomic diversity of bacteria from root nodules of G. saharae growing in the infra-arid region of Tunisia was investigated. METHODS AND RESULTS: A total of 28 bacterial strains isolated from root nodules of G. saharae grown in Tunisian soil were characterized using a polyphasic approach including phenotypic characteristics, PCR-RFLP of 16S rDNA and 16S rRNA gene sequencing. It was found that new isolates are diverse and affiliated to Ensifer (75%), Rhizobium (10%) and Phyllobacterium (15%). The Phyllobacterium isolates lacked the capacity for nodule formation on this plant. CONCLUSIONS: Genista saharae formed nodules with diverse rhizobia in Tunisian soils. Furthermore, our results support the presence of non-nodulating commensal strains (Phyllobacterium) in legumes nodule. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first report on the characterization of G. saharae microsymbionts in Tunisia.