title: Diverse Bacteria Affiliated with the Genera Microvirga, Phyllobacterium, and Bradyrhizobium Nodulate Lupinus micranthus Growing in Soils of Northern Tunisia.
abstract: The genetic diversity of bacterial populations nodulatingLupinus micranthusin five geographical sites from northern Tunisia was examined. Phylogenetic analyses of 50 isolates based on partial sequences ofrecAandgyrBgrouped strains into seven clusters, five of which belong to the genusBradyrhizobium(28 isolates), one toPhyllobacterium(2 isolates), and one, remarkably, toMicrovirga(20 isolates). The largestBradyrhizobiumcluster (17 isolates) grouped with theB. lupinispecies, and the other five clusters were close to different recently definedBradyrhizobiumspecies. Isolates close toMicrovirgawere obtained from nodules of plants from four of the five sites sampled. We carried out an in-depth phylogenetic study with representatives of the seven clusters using sequences from housekeeping genes (rrs,recA,glnII,gyrB, anddnaK) and obtained consistent results. A phylogeny based on the sequence of the symbiotic genenodCidentified four groups, three formed byBradyrhizobiumisolates and one by theMicrovirgaandPhyllobacteriumisolates. Symbiotic behaviors of the representative strains were tested, and some congruence between symbiovars and symbiotic performance was observed. These data indicate a remarkable diversity ofL. micranthusroot nodule symbionts in northern Tunisia, including strains from theBradyrhizobiaceae,Methylobacteriaceae, andPhyllobacteriaceaefamilies, in contrast with those of the rhizobial populations nodulating lupines in the Old World, includingL. micranthusfrom other Mediterranean areas, which are nodulated mostly byBradyrhizobiumstrains.IMPORTANCELupinus micranthusis a legume broadly distributed in the Mediterranean region and plays an important role in soil fertility and vegetation coverage by fixing nitrogen and solubilizing phosphate in semiarid areas. Direct sowing to extend the distribution of this indigenous legume can contribute to the prevention of soil erosion in pre-Saharan lands of Tunisia. However, rhizobial populations associated withL. micranthusare poorly understood. In this context, the diversity of endosymbionts of this legume was investigated. MostLupinusspecies are nodulated byBradyrhizobiumstrains. This work showed that about half of the isolates from northern Tunisian soils were in factBradyrhizobiumsymbionts, but the other half were found unexpectedly to be bacteria within the generaMicrovirgaandPhyllobacteriumThese unusual endosymbionts may have a great ecological relevance. Inoculation with the appropriate selected symbiotic bacterial partners will increaseL. micranthussurvival with consequent advantages for the environment in semiarid areas of Tunisia.
authors.affiliation: Research Unit Biodiversity and Valorization of Arid Areas Bioresources (BVBAA), Faculty of Sciences of Gabès Erriadh, Zrig,Tunisia.
authors.forename: Abdelhakim
authors.initials: A
authors.lastname: Msaddak
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA), ETSI Agronómica, Alimentaria y de Biosistemas, Campus de Montegancedo, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Durán
authors.affiliation: Research Unit Biodiversity and Valorization of Arid Areas Bioresources (BVBAA), Faculty of Sciences of Gabès Erriadh, Zrig,Tunisia.
authors.forename: Mokhtar
authors.initials: M
authors.lastname: Rejili
authors.affiliation: Research Unit Biodiversity and Valorization of Arid Areas Bioresources (BVBAA), Faculty of Sciences of Gabès Erriadh, Zrig,Tunisia.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Mars
authors.affiliation: CSIC, Madrid, Spain.
authors.forename: Tomás
authors.initials: T
authors.lastname: Ruiz-Argüeso
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA), ETSI Agronómica, Alimentaria y de Biosistemas, Campus de Montegancedo, Universidad Politécnica de Madrid, Madrid, Spain.|CSIC, Madrid, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Imperial
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA), ETSI Agronómica, Alimentaria y de Biosistemas, Campus de Montegancedo, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Palacios
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA), ETSI Agronómica, Alimentaria y de Biosistemas, Campus de Montegancedo, Universidad Politécnica de Madrid, Madrid, Spain luis.rey@upm.es.
authors.forename: Luis
authors.identifier: http://orcid.org/0000-0003-3477-6942
authors.initials: L
authors.lastname: Rey
mesh_terms: D044822:Biodiversity; D020369:Bradyrhizobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D027081:DNA Gyrase / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D020043:Genes, Essential / Q000235:genetics; D031297:Lupinus / Q000382:microbiology*; D042082:Methylobacteriaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D059127:Phyllobacteriaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D010802:Phylogeny; D055170:Plant Root Nodulation / Q000502:physiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011938:Rec A Recombinases / Q000235:genetics; D053204:Root Nodules, Plant / Q000382:microbiology*; D012988:Soil Microbiology; D013559:Symbiosis / Q000502:physiology; D014416:Tunisia
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D011938:Rec A Recombinases; D027081:DNA Gyrase
keywords: Bradyrhizobium; Lupinus micranthus; Microvirga; Phyllobacterium; nodulation