title: Metabolic capacity of Sinorhizobium (Ensifer) meliloti strains as determined by phenotype MicroArray analysis.
abstract: Sinorhizobium meliloti is a soil bacterium that fixes atmospheric nitrogen in plant roots. The high genetic diversity of its natural populations has been the subject of extensive analysis. Recent genomic studies of several isolates revealed a high content of variable genes, suggesting a correspondingly large phenotypic differentiation among strains of S. meliloti. Here, using the Phenotype MicroArray (PM) system, hundreds of different growth conditions were tested in order to compare the metabolic capabilities of the laboratory reference strain Rm1021 with those of four natural S. meliloti isolates previously analyzed by comparative genomic hybridization (CGH). The results of PM analysis showed that most phenotypic differences involved carbon source utilization and tolerance to osmolytes and pH, while fewer differences were scored for nitrogen, phosphorus, and sulfur source utilization. Only the variability of the tested strain in tolerance to sodium nitrite and ammonium sulfate of pH 8 was hypothesized to be associated with the genetic polymorphisms detected by CGH analysis. Colony and cell morphologies and the ability to nodulate Medicago truncatula plants were also compared, revealing further phenotypic diversity. Overall, our results suggest that the study of functional (phenotypic) variability of S. meliloti populations is an important and complementary step in the investigation of genetic polymorphism of rhizobia and may help to elucidate rhizobial evolutionary dynamics, including adaptation to diverse environments.
authors: Department of Evolutionary Biology, University of Florence, Via Romana 17, Florence, Italy. emanuele.biondi@unifi.it
authors: Emanuele G
authors: EG
authors: Biondi
authors: Enrico
authors: E
authors: Tatti
authors: Diego
authors: D
authors: Comparini
authors: Elisa
authors: E
authors: Giuntini
authors: Stefano
authors: S
authors: Mocali
authors: Luciana
authors: L
authors: Giovannetti
authors: Marco
authors: M
authors: Bazzicalupo
authors: Alessio
authors: A
authors: Mengoni
authors: Carlo
authors: C
authors: Viti
mesh_terms: D015373:Bacterial Typing Techniques; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis*; D046913:Medicago truncatula / Q000382:microbiology*; D008858:Microscopy, Phase-Contrast; D009586:Nitrogen Fixation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D016962:Sinorhizobium meliloti / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012988:Soil Microbiology; D013045:Species Specificity
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial