The objective of the study is to characterise the taxonomy of the thermophilic filamentous strain B121 isolated from the hot springs in Ganzi, Sichuan, and provide insight into its genetic basis for future application. The taxonomy of strain B121 was analyzed by using polyphasic approach encompassing genome analysis, phylogenetic analysis, secondary structure prediction, and overall analysis of morphology, sodium salt tolerance test combined nitrogen fixation ability. Phylogenetic analysis of 16S rRNA indicated that strain B121 closely clustered with strains Thermoleptolyngbya oregonensis PCC 8501, Thermoleptolyngbya albertanoae ETS-08 and Thermoleptolyngbya sp.O-77; the 16S-23S ITS secondary structure prediction showed that the D1-D1' region of strain B121 has certain similarity and high sequence identity with reference strains, but they have not reached the generalized threshold for the same species. Additionally, the secondary structures of V2, BoxB and V3 regions are quite different between B121 and other reference strains. Combined with the analysis of morphological investigation, strain B121 was identified as a new species of the genus Thermoleptolyngbya. In addition, the strain B121 can survive in NaCl and NaNO3 modified BG-11 medium with a concentration of 0.5 M, and it can also survive in NaCl modified BG-11 medium with a concentration of 1 M. When the gas phase condition is Ar:N₂:CO₂ = 79:20:1 (v:v:v), the acetylene reduction rate of strain B121 can reach 2564.1 nmol/(g·h). 

为了确定分离自四川甘孜地区温泉的嗜热丝状菌株B121的分类信息, 为探索其应用价值提供遗传学分析基础, 对其进行基因组分析、系统发育分析、二级结构预测、形态学鉴定以及结合菌株钠盐耐受性和固氮能力的整体分析。在16S rRNA的系统发育分析中, 发现菌株 B121与菌株Thermoleptolyngbya oregonensis PCC 8501, Thermoleptolyngbya albertanoae ETS-08和Thermoleptolyngbya sp.O-77等嗜热鞘丝藻属菌株有较好的聚类。在16S-23S ITS二级结构预测分析中, 菌株B121的D1-D1'区域与属内参考菌株有一定的相似性, 序列同一性也较高, 但都没有到达广义的同种物种标准, 并且V2, BoxB及V3区域与其他对照菌株的差异较大。结合形态学分析, 确定菌株B121 是Thermoleptolyngbya属下的一个新种。菌株B121可在最高浓度为0.5 M的NaCl和NaNO₃培养基中生存, 也可在浓度为1 M的NaCl培养基中存活。当气相条件为Ar:N₂: CO₂=79:20:1 (体积比)时, 菌株B121的乙炔还原速率可以达到2564.1 nmol/(g·h)。