title: Stress tolerance and symbiotic and phylogenic features of root nodule bacteria associated with Medicago species in different bioclimatic regions of Tunisia.
abstract: Thirty two rhizobial isolates were obtained from different bioclimatic regions of Tunisia using as trap plants, Medicago sativa, Medicago ciliaris, Medicago polymorpha and Medicago minima. To study their diversity and characterize them in relation to Mediterranean conditions, abiotic stress resistance, symbiotic properties and genetic diversity in terms of 16S rRNA and nodA sequences were assessed. Five isolates from M. sativa, three from M. ciliaris and three from M. minima could grow at 45°C. Only two isolates from M. sativa grew at 4% NaCl. The most stress tolerant isolates were obtained from arid soils. A phylogenetic analysis of 16S rRNA genes revealed 29 isolates to be closely related to Ensifer including one (Pl.3-9) that showed a 16S rRNA sequence similar to that of Ensifer meliloti and nodA sequence similar to that of Ensifer medicae. However, three isolates were categorized into Agrobacterium containing the nodA of Ensifer. Furthermore, these isolates developed nodules on original hosts. The results for the four isolates suggest horizontal gene transfer between the species.
authors.affiliation: United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3–5–8 Saiwai-cho, Fuchu, Tokyo 183–8509, Japan.
authors.forename: Salem
authors.initials: S
authors.lastname: Djedidi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Naoko
authors.initials: N
authors.lastname: Ohkama-Ohtsu
authors.forename: Chandra Prasad
authors.initials: CP
authors.lastname: Risal
authors.forename: Chedly
authors.initials: C
authors.lastname: Abdelly
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sekimoto
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D002980:Climate; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D029902:Medicago / Q000382:microbiology* / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D053204:Root Nodules, Plant / Q000382:microbiology* / Q000502:physiology; D012965:Sodium Chloride / Q000378:metabolism; D012988:Soil Microbiology; D013312:Stress, Physiological; D013559:Symbiosis; D014416:Tunisia
chemical_list: D012965:Sodium Chloride