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Paenibacillus helianthi sp. nov., a nitrogen fixing species isolated from the rhizosphere of Helianthus annuus L.

Ambrosini, Adriana, Sant’Anna, Fernando Hayashi, Heinzmann, Júlia, de Carvalho Fernandes, Gabriela, Bach, Evelise, Passaglia, Luciane Maria Pereira
Antonie van Leeuwenhoek 2018 v.111 no.12 pp. 2463-2471
Helianthus annuus, Paenibacillus, ammonia, bacteria, fatty acid composition, fatty acids, genes, genomics, new species, nitrogen fixation, nucleic acid hybridization, nucleotide sequences, phenotype, phylogeny, proteome, rhizosphere, ribosomal DNA, ribosomal RNA, Brazil
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.