Niveispirillum cyanobacteriorum sp nov., a nitrogen-fixing bacterium isolated from cyanobacterial aggregates in a eutrophic lake

A Gram-stain-negative, slightly curved rod-shaped, non-spore-forming diazotrophic bacterium, designated strain TH16(T), was isolated from cyanobacterial aggregates taken from eutrophic Lake Taihu, Jiangsu Province, China. The pH range for growth was 5-9 (optimum at pH 7.0), salinity range was 0-2 % (w/v) NaCI (optimum 0 %) and temperature range was 20-37 degrees C (optimum 30 degrees C) in nutrient broth. Phylogenetic analysis indicated that strain TH16(T) clusters near and is closely related to the genus Niveispirillum within the family Rhodospirillaceae of the class Alphaproteobacteria. Within the genus Niveispirillum, strain TH16(T) was related most closely to Niveispirillum irakense KBC1(T) (98.1 % 16S rRNA gene sequence similarity) and Niveispirillum fermenti CC-LY736(T) (97.0 %). The DNA G+C content of strain TH16(T) was 64 mol%. DNA DNA relatedness between strain TH16(T) and the type strains of N. irakense and N. fermenti was 39.6 and 30.1 %, respectively. The major respiratory quinone was ubiquinone 0-10.The major fatty acids (>10 %) were C-18:1 omega 6C/C-18:1 omega 7c, C(18:1)2-OH and C(16:0)3-OH. Genes in the puf operon, encoding proteins of the photosynthetic reaction centre and core light-harvesting complexes, were also present. Based on morphological, chemotaxonomic and phylogenetic data, strain TH16(T) represents a novel species within the genus Niveispirillum, for which the name Niveispirillum cyanobacteriorum sp. nov. is proposed. The type strain is TH16(T) (=CGMCC 1.12958(T)=LMG 28334(T)).