Noviherbaspirillum denitrificans sp nov., a denitrifying bacterium isolated from rice paddy soil and Noviherbaspirillum autotrophicum sp nov., a denitrifying, facultatively autotrophic bacterium isolated from rice paddy soil and proposal to reclassify Herbaspirillum massiliense as Noviherbaspirillum massiliense comb. nov.

Thirty-nine denitrifying bacterial strains closely related to one another, represented by strains TSA40(T) and TSA66(T), were isolated from rice paddy soils. Strains TSA40(T) and TSA66(T) were Gram-stain-negative, slightly curved rod-shaped, and motile by means of polar flagella. They were able to reduce nitrate, nitrite and nitrous oxide, but unable to fix atmospheric N-2. While strain TSA66(T) was able to grow autotrophically by H-2-dependent denitrification, strain TSA40(T) could not. Phylogenetic analysis suggested that they belong to the family Oxalobacteraceae, the order Burkholderiales in the class Betaproteobacteria. Major components in the fatty acids (C-16 : 0, C-17 : 0 cyclo, C-18 : 1 omega 7c and summed feature 3) and quinone (Q-8) also supported the affiliation of strains TSA40(T) and TSA66(T) to the family Oxalobacteraceae. Based on 16S rRNA gene sequence comparisons, strains TSA40(T) and TSA66(T) showed the greatest degree of similarity to Herbaspirillum massiliense JC206(T), Noviherbaspirillum malthae CC-AFH3(T), Noviherbaspirillum humi U15(T), Herbaspirillum seropedicae Z67(T) and Paucimonas lemoignei LMG 2207(T), and lower similarities to the members of other genera. Average nucleotide identity values between the genomes of strain TSA40(T), TSA66(T) and H. massiliense JC206(T) were 75-77 %, which was lower than the threshold value for species discrimination (9596 %). Based on the 16S rRNA gene sequence analysis in combination with physiological, chemotaxonomic and genomic properties, strains TSA40(T) (= JCM 17722(T) = ATCC TSD-69(T)) and TSA66(T) (= JCM 17723(T) = DSM 25787(T)) are the type strains of two novel species within the genus Noviherbaspirillum, for which the names Noviherbaspirillum denitrificans sp. nov. and Noviherbaspirillum autotrophicum sp. nov. are proposed, respectively. We also propose the reclassification of Herbaspirillum massiliense as Noviherbaspirillum massiliense comb. nov.