Azospirillum Agricola Sp Nov., A Nitrogen-Fixing Species Isolated From Cultivated Soil

A polyphasic approach was used to characterize a novel nitrogen -fixing bacterial strain, designated CC-HIH038(T), isolated from cultivated soil in Taiwan. Cells of strain CC-HIH038(T) were Gram-stain-negative, facultatively aerobic and spiral-shaped, with motility provided by a single polar flagellum. The 16S rRNA gene sequence analysis of strain CC-HIH038(T) showed highest sequence similarity to Azospirillum doebereinerae (98.0%), Azospirillum thiophilum (97.5%), Azospirillum rugosum (97.4%) and Azospirillum zeae (97.2%) and lower sequence similarity (<97.0%) to all other species of the genus Azospirillum. According to DNA -DNA association, the relatedness values of strain CC-HIH038(T) with A. doebereinerae, A. thiophilum, A. rugosum and A. zeae were 51.8%, 41.2%, 56.5 % and 37.5%, respectively. Strain CC-HIH038(T) was able to grow at 20-37 C and pH 7.0-8.0. Strain CC-HIH038(T) gave positive amplification for dinitrogen reductase (nifH gene); the activity was recorded as 8.4 nmol ethylene h-1. The predominant quinone system was ubiquinone Q-10 and the DNA G + C content was 68.8 mol%. The major fatty acids found in strain CC-HIH038(T) were C16:0, iSO-Ci(8:0), C-16:0 3-OH, C-14:0 3-OH/iSO-C-16 :1 and C-18:1(omega 7C/C-18:10 omega c. Based on the distinct phylogenetic, phenotypic and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence analysis, strain CC-HIH038T is considered to represent a novel species in the genus Azospirillum, for which the name Azospirillum agricola sp. nov. is proposed. The type strain is CC-HIH038(T) (=BCRC 80909(T)=JCM 30827(T)).