Abstract
A novel diazotrophic bacterium, designated CCTCC AB 2021101T, was isolated from fresh roots of kiwifruit. Cells of strain CCTCC AB 2021101T were Gram-negative, aerobic and rod-shaped, with motility provided by peritrichous flagella. The 16S rRNA analysis showed that strain CCTCC AB 2021101T belongs to the genus Azospirillum and is closely related to Azospirillum melinis (98.32%), Azospirillum oryzae (97.73%), Azospirillum lipoferum (96.98%), Azospirillum humicireducens (96.49%) and Azospirillum largimobile (96.01%) and lower sequence similarity (<96.0 %) to all other species of the genus Azospirillum. Strain CCTCC AB 2021101T was able to grow well at 35–40℃ and pH 6.0–7.0, and tolerated up to 3.0 % (w/v) NaCl. The major saturated fatty acids are C14:0, C16:0 and C18:0. C18:1 ω7c and C16:0 3-OH were the major unsaturated and hydroxylated fatty acid. The G+C content was 67.8 mol%. Strain CCTCC AB 2021101T gave positive amplification for dinitrogen reductase (nifH gene). Highest nifH gene sequence similarities were obtained with Azospirillum brasilense AWB14T(95.9%), Azospirillum zeae Gr24T(95.56%), Azospirillum picis DSM 19922T(96.79%), Azospirillum lipoferum B22T(94.88%) and Azospirillum oryzae COC8T(94.88%). The activity of the nitrogenase of the strain was further confirmed by acetylene-reduction assay, which was recorded as 81 nmol ethylene h-1. Based on these data, strain CCTCC AB 2021101T is considered to represent a novel endophytic diazotrophs species in the genus Azospirillum, for which the name Azospirillum actinidiae sp. nov. is proposed. The type strain is CCTCC AB 2021101T.