Paenibacillus zanthoxyli sp. nov., a novel nitrogen-fixing species isolated from the rhizosphere of Zanthoxylum simulans.

Five endospore-forming, nitrogen-fixing strains were isolated from rhizosphere soils of Zanthoxylum simulans planted in Beijing, China. Phylogenetic analysis based on full-length 16S rRNA gene sequences revealed that the five strains formed a distinct cluster within the genus Paenibacillus. High levels of 16S rRNA gene sequence similarity were found between these novel strains and Paenibacillus azotofixans ATCC 35681(T) (97.8-98.5 % similarity) and Paenibacillus stellifer DSM 14472(T) (95.4-96.3 %). Levels of 16S rRNA gene sequence similarity between the novel isolates and other species of the genus Paenibacillus were less than 95.0 %. Levels of 16S rRNA gene sequence similarity among the isolates were more than 98.0 %. DNA-DNA relatedness between the five novel isolates and P. azotofixans ATCC 35681(T) was 45.50-47.45 % and relatedness among the five novel strains was 95.8-99.6 %. A significant feature of the novel strains that differentiated them from P. azotofixans and other Paenibacillus species was that none of the novel strains could produce acid or gas from the following various carbohydrates: glucose, sucrose, lactose, fructose, glycerol, xylose, maltose, d-sorbitol, sodium succinate, sodium citrate, glycine or l-aspartate. Anteiso-branched C(15 : 0) was the major fatty acid component (36.59 %) of novel strain JH29(T). On the basis of phenotypic properties, 16S rRNA gene sequences, DNA G+C content, DNA-DNA hybridization, chemotaxonomic properties and the nifH gene sequence, the five novel strains form a very homogeneous group which is different from other related species within the genus Paenibacillus. Therefore, the five novel strains are considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus zanthoxyli sp. nov. is proposed. The type strain is JH29(T) (=CCBAU 10243(T)=DSM 18202(T)).