RESUMO
Azospirillum sp. strain Sp245T, originally identified as belonging to Azospirillum brasilense, is recognized as a plant-growth-promoting rhizobacterium due to its ability to fix atmospheric nitrogen and to produce plant-beneficial compounds. Azospirillum sp. Sp245T and other related strains were isolated from the root surfaces of different plants in Brazil. Cells are Gram-negative, curved or slightly curved rods, and motile with polar and lateral flagella. Their growth temperature varies between 20 to 38 °C and their carbon source utilization is similar to other Azospirillum species. A preliminary 16S rRNA sequence analysis showed that the new species is closely related to A. brasilense Sp7T and A. formosense CC-Nfb-7T. Housekeeping genes revealed that Azospirillum sp. Sp245T, BR 12001 and Vi22 form a separate cluster from strain A. formosense CC-Nfb-7T, and a group of strains closely related to A. brasilense Sp7T. Overall genome relatedness index (OGRI) analyses estimated based on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) between Azospirillum sp. Sp245T and its close relatives to other Azospirillum species type strains, such as A. brasilense Sp7T and A. formosense CC-Nfb-7T , revealed values lower than the limit of species circumscription. Moreover, core-proteome phylogeny including 1079 common shared proteins showed the independent clusterization of A. brasilense Sp7T, A. formosense CC-Nfb-7T and Azospirillum sp. Sp245T, a finding that was corroborated by the genome clustering of OGRI values and housekeeping phylogenies. The DNA G+C content of the cluster of Sp245T was 68.4-68.6â%. Based on the phylogenetic, genomic, phenotypical and physiological analysis, we propose that strain Sp245T together with the strains Vi22 and BR12001 represent a novel species of the genus Azospirillum, for which the name Azospirillum baldaniorum sp. nov. is proposed. The type strain is Sp245T (=BR 11005T=IBPPM 219T) (GCF_007827915.1, GCF_000237365.1, and GCF_003119195.2).
Assuntos
Azospirillum brasilense/classificação , Azospirillum/classificação , Genoma Bacteriano , Filogenia , Técnicas de Tipagem Bacteriana , Composição de Bases , Brasil , DNA Bacteriano/genética , Flagelos/química , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
Bacteria of the genus Paenibacillus are relevant to humans, animals and plants. The species Paenibacillus massiliensis and Paenibacillus panacisoli are Gram-stain-positive and endospore-forming bacilli isolated from a blood culture of a leukemia patient and from soil of a ginseng field, respectively. Comparative analyses of their 16S rRNA genes revealed that the two Paenibacillus species could be synonyms (99.3% sequence identity). In the present study we performed different genomic analyses in order to evaluate the phylogenetic relationship of these micro-organisms. Paenibacillus massiliensis DSM 16942T and P. panacisoli DSM 21345T presented a difference in their G+C content lower than 1âmol%, overall genome relatedness index values higher than the species circumscription thresholds (average nucleotide identity, 95.57â%; genome-wide ANI, =96.51â%; and orthologous ANI, 96.25â%), and a monophyletic grouping pattern in the phylogenies of the 16S rRNA gene and the proteome core. Considering that these strains present differential biochemical capabilities and that their computed digital DNA-DNA hybridization value is lower than the cut-off for bacterial subspecies circumscription, we suggest that each of them form different subspecies of P. massiliensis, Paenibacillus massiliensis subsp. panacisoli subsp. nov. (type strain DSM 21345T) and Paenibacillus massiliensis subsp. massiliensis subsp. nov. (type strain DSM 16942T).
Assuntos
Paenibacillus/classificação , Filogenia , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Genes Bacterianos , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
Three facultatively anaerobic endospore-forming bacteria were isolated from the rhizosphere of sunflowers grown in fields of Rio Grande do Sul State, Brazil. The designated type strain P26ET was previously identified as a sunflower growth promoting bacterium and is able to fix nitrogen and to excrete ammonia. According to analyses of 16S rRNA gene sequences, P26ET presented similarity values above 98.8% in relation to Paenibacillus azotifigens NF2-4-5T, Paenibacillus graminis RSA19T, Paenibacillus jilunlii Be17T, Paenibacillus salinicaeni LAM0A28T, and Paenibacillus sonchi X19-5T. Phylogenetic reconstructions based on 16S rRNA gene and core proteome data showed that the strains P26ET, P3E and P32E form a distinct clade, which did not include any type strain of the currently described Paenibacillus species. Also, genomic comparisons using average nucleotide identity (ANI), Orthologous ANI and in silico DNA-DNA hybridization revealed similarity ranges below the recommended thresholds when the three isolates from sunflower were compared to their close relatives. The DNA G + C content of strain P26ET was determined to be 49.4 mol%. The major cellular fatty acids are anteiso-C15:0 and iso-C15:0, representing about 58 and 14% of the total fatty acids in P26ET, respectively. Based on different taxonomic genomic metrics, phylogeny, and phenotypic data, we propose that strain P26ET (= DSM 102269 = BR10509) represents a novel species within the genus Paenibacillus, for which the name Paenibacillus helianthi sp. nov. is proposed.