RESUMO
Conzattia multiflora is a leguminous tree present only in Mexico and Guatemala. There is no record about its symbiotic or pathogenic microbes. In this study, we found that numerous bacteria with 10(4)-10(6) individuals per gram of fresh epidermis were distributed in the tissue of this plant. All the bacteria isolated from the Conzattia epidermis were Gram-negative, facultative anaerobic rods and formed yellow or colorless colonies. They were identified as endophytes by inoculation tests. Some of the bacteria could significantly promote the growth of Conzattia seedlings. Nine different groups were defined by PCR-based RFLP, which were classified as Pantoea, Erwinia, Salmonella, Enterobacter, Citrobacter and Klebsiella by the phylogenetic analysis of 16S rRNA genes. The existence of plant-borne lineages of Salmonella indicates that the unexplored plants may harbor some unknown microbes.
Assuntos
Fabaceae/microbiologia , Bacilos Gram-Negativos Anaeróbios Facultativos/classificação , Bacilos Gram-Negativos Anaeróbios Facultativos/isolamento & purificação , Árvores/microbiologia , Acetileno/metabolismo , DNA Bacteriano/análise , Fabaceae/crescimento & desenvolvimento , Bacilos Gram-Negativos Anaeróbios Facultativos/genética , Bacilos Gram-Negativos Anaeróbios Facultativos/crescimento & desenvolvimento , México , Dados de Sequência Molecular , Oxirredução , Filogenia , Estruturas Vegetais/microbiologia , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genética , Simbiose , Árvores/crescimento & desenvolvimentoRESUMO
Forty-six Mesorhizobium strains associated with the leguminous plants Leucaena leucocephala and Sesbania herbacea in an uncultivated Mexican field were characterized using a polyphasic approach. The strains were identified as Mesorhizobium plurifarium based upon the close relationships with the reference strains for this species in PCR-based restriction fragment length polymorphism analyses, sequencing of 16S rRNA genes, multilocus enzyme electrophoresis, and DNA-DNA hybridization. Although the strains isolated from both plants formed the same group in multilocus enzyme electrophoresis and cross-nodulations were observed in the laboratory, different electrophoretic types were obtained from the two plants grown in natural soils, indicating the existence of a preferable association between the plants and the rhizobia. The M. plurifarium strains from Mexico and the reference strains from Africa and Brazil formed different phenotypic clusters in a numerical taxonomy. The Mexican strains did not grow at 37 degrees C and were sensitive to salty-alkaline conditions, while the reference strains from Africa and Brazil grew at 42 degrees C and were more resistant to salty-alkaline conditions. These results demonstrate that both the plants and environmental factors affected the evolution of rhizobia and that the Mexican strains had adapted to the neutral soils and the cool climate where they were isolated.
Assuntos
Alphaproteobacteria/classificação , Alphaproteobacteria/isolamento & purificação , Biodiversidade , Fabaceae/microbiologia , Microbiologia do Solo , Adaptação Biológica , Alphaproteobacteria/crescimento & desenvolvimento , Proteínas de Bactérias/análise , Proteínas de Bactérias/isolamento & purificação , Evolução Biológica , DNA Ribossômico/química , DNA Ribossômico/isolamento & purificação , Variação Genética , Concentração de Íons de Hidrogênio , México , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Pressão Osmótica , Filogenia , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Cloreto de Sódio , TemperaturaRESUMO
Sinorhizobium morelense sp. nov. is described to designate a group of bacteria isolated from root nodules of Leucaena leucocephala. S. morelense shows 98% 16S rRNA gene sequence similarity to some Sinorhizobium species and to Ensifer adhaerens. This novel species is distinguished from other Sinorhizobium species and from E. adhaerens by DNA-DNA hybridization, 165 rRNA gene restriction fragments and sequence and some distinctive phenotypic features. Strains of this species are highly resistant to some antibiotics, such as carbenicillin (1 mg ml(-1)), kanamycin (500 microg ml(-1)) and erythromycin (300 microg ml(-1)). They do not form nodules, but a nodulating strain, Lc57, is closely related to the novel species. Strain Lc04T (= LMG 21331T = CFN E1007T) is designated as the type strain of this novel species.