Azospirillum soli sp. nov., a nitrogen-fixing species isolated from agricultural soil

An aerobic, Gram-stain-negative, rod or spiral-shaped diazotrophic bacterium (designated strain CC-LY788T), was isolated from agricultural soil in Taiwan. Strain CC-LY788T was able to grow at 25-40 °C, pH 6.0-8.0 and tolerated NaCl to 2.0% (w/v). Positive for nitrogen fixation with the activity recorded as 6.5 nmol ethylene h(-1). Strain CC-LY788T showed highest 16S rRNA gene sequence similarity to Azospirillum picis DSM 19922T (97.2%) and Azospirillum rugosum DSM 19657T (97.1%) and lower sequence similarities (<96.6%) to all other species of the genus Azospirillum. According to the DNA-DNA hybridization, the relatedness values of strain CC-LY788T with A. picis DSM 19922T and A. rugosum DSM 19657T were 51.1±5.5% and 46.8±2.1%, respectively. Strain CC-LY788T was positive for the rapid identification of the genus-specific primer set. The respiratory quinone system was ubiquinone (Q-10) and the DNAG+C content was 69.8 mol%. The major fatty acids found in strain CC-LY788T were C16 : 0, C18 : 1 2-OH, C14 : 0 3-OH/C16 : 1 iso I (summed feature 2), C16 : 1ω7c/C16 : 1ω6c (summed feature 3), C18 : 0 ante/C18 : 2ω6,9c (summed feature 5) and C18 : 1ω7c/C18 : 1ω6c (summed feature 8). Based on the phylogenetic, phenotypic and chemotaxonomic features, strain CC-LY788T represents a novel species of the genus Azospirillum, for which the name Azospirillum soli sp. nov. is proposed. The type strain is CC-LY788T (=BCRC 80569T=JCM 18820T).