RESUMO
Two free-living nitrogen-fixing bacterial strains, N6 and N7(T), were isolated from corn rhizosphere. A polyphasic taxonomic approach, including morphological characterization, Biolog analysis, DNA-DNA hybridization, and 16S rRNA, cpn60 and nifH gene sequence analysis, was taken to analyse the two strains. 16S rRNA gene sequence analysis indicated that strains N6 and N7(T) both belonged to the genus Azospirillum and were closely related to Azospirillum oryzae (98.7 and 98.8 % similarity, respectively) and Azospirillum lipoferum (97.5 and 97.6 % similarity, respectively). DNA-DNA hybridization of strains N6 and N7(T) showed reassociation values of 48 and 37 %, respectively, with A. oryzae and 43 % with A. lipoferum. Sequences of the nifH and cpn60 genes of both strains showed 99 and approximately 95 % similarity, respectively, with those of A. oryzae. Chemotaxonomic characteristics (Q-10 as quinone system, 18 : 1omega7c as major fatty acid) and G+C content of the DNA (67.6 mol%) were also similar to those of members of the genus Azospirillum. Gene sequences and Biolog and fatty acid analysis showed that strains N6 and N7(T) differed from the closely related species A. lipoferum and A. oryzae. On the basis of these results, it is proposed that these nitrogen-fixing strains represent a novel species. The name Azospirillum zeae sp. nov. is suggested, with N7(T) (=NCCB 100147(T)=LMG 23989(T)) as the type strain.
Assuntos
Azospirillum/classificação , Azospirillum/isolamento & purificação , Raízes de Plantas/microbiologia , Microbiologia do Solo , Zea mays/microbiologia , Azospirillum/química , Azospirillum/genética , Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana , Composição de Bases , Chaperonina 60/genética , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Ácidos Graxos/análise , Genes de RNAr , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Fixação de Nitrogênio/fisiologia , Hibridização de Ácido Nucleico , Oxirredutases/genética , Filogenia , Quinonas/análise , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Homologia de Sequência do Ácido NucleicoRESUMO
A free-living Gram-negative bacterial strain CR11(T) was isolated from corn roots. Polyphasic taxonomy was performed, including API20 NE and API50 CH bacterial identification kits, Biolog analysis, lipids and fatty acid analysis, DNA-DNA hybridization, 16S rRNA and cpn60 gene sequence analyses. 16S rRNA gene sequence analysis indicated that strain CR11(T) belonged to the genus Sphingobacterium and was closely related to Sphingobacterium multivorum IFO 14947(T) (98% similarity) and Sphingobacterium. thalpophilum ATCC 43320(T) (97% similarity). DNA-DNA hybridization showed 11% and 13% DNA re-association with S. multivorum LMG 8342(T) and S. thalpophilum LMG 11520(T), respectively. Major fatty acids (16:0, 15:0 iso and 17:0 iso 3-OH) and the G+C content of the DNA (40.5 mol%), were also similar to those of the genus Sphingobacterium. The predominant respiratory quinone was MK-7. In all analyses, including phenotypic characterization, this isolate was found to be different from the closely related species, S. multivorum and S. thalpophilum. On the basis of these results, this strain represents a new species within the genus Sphingobacterium. The name Sphingobacterium canadense sp. nov. is suggested and the type strain is CR11(T) (=NCCB 100125(T)=LMG 23727(T)).
Assuntos
Raízes de Plantas/microbiologia , Sphingobacterium/classificação , Sphingobacterium/isolamento & purificação , Zea mays/microbiologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Chaperonina 60/genética , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Ácidos Graxos/análise , Genes de RNAr , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Fosfolipídeos/análise , Filogenia , Quinonas/análise , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Sphingobacterium/química , Sphingobacterium/genéticaRESUMO
A free-living diazotrophic strain, DS2(T), was isolated from corn rhizosphere. Polyphasic taxonomy was performed including morphological characterization, Biolog analysis, and 16S rRNA, cpn60 and nifH gene sequence analyses. 16S rRNA gene sequence analysis indicated that strain DS2(T) was closely related to the genus Azospirillum (96 % similarity). Chemotaxonomic characteristics (DNA G+C content 67.9 mol%; Q-10 quinone system; major fatty acid 18 : 1omega7c) were also similar to those of the genus Azospirillum. In all the analyses, including phenotypic characterization using Biolog analysis and comparison of cellular fatty acids, this isolate was found to be different from the closely related species Azospirillum lipoferum, Azospirillum oryzae and Azospirillum brasilense. On the basis of these results, a novel species is proposed for this nitrogen-fixing strain. The name Azospirillum canadense sp. nov. is suggested with the type strain DS2(T) (=NCCB 100108(T)=LMG 23617(T)).