National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Resources and Environment of Shandong Agricultural University, Taian 271000, China.
Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.
Syst Appl Microbiol. 2022 Jul;45(4):126337. doi: 10.1016/j.syapm.2022.126337. Epub 2022 May 26.
Aeschynomene indica has a distinctive symbiosis with Bradyrhizobium in which nodulation is Nod factor-independent. In this study, we characterised three Gram-negative and rod-shaped strains (83002, 81013 and 83012) isolated from root nodules of Aeschynomene indica in Shandong Peninsula. The major cellular fatty acids of isolates were C, C, C ω7c 11-methyl, summed feature 3 and summed feature 8. The major polar lipids were phosphatidylethanolamine (PE), aminolipids (AL) and phosphatidylcholine (PC). Phylogenetic analysis based on the 16S rRNA locus showed that they belonged to the Bradyrhizobium genus, and shared the highest similarity to the type strains Bradyrhizobium oligotrophicum S58 and Bradyrhizobium denitrificans LMG 8443. As expected, analysis of concatenated sequences of six housekeeping genes (atpD, recA, glnII, dnaK, gyrB, and rpoB) and nifH gene proposed that these three strains formed a distinct clade within the genus Bradyrhizobium. The highest average nucleotide identity and DNA-DNA hybridization values of the three strains in comparison to the closest Bradyrhizobium species were 87.5% and 65.3%, respectively, which are far below the threshold of species delineation, and thus confirmed the three strains as a new species. The genome size of strain 83002 is 7.52 Mbp, and the DNA G+C content is 65.42 mol%. Strain 83002 (=KCTC 82266=MCCC 1K04775) was chosen as the type strain of the new species, for which the name Bradyrhizobium aeschynomenes sp. nov. was proposed.
鸡眼草（Aeschynomene indica）与慢生根瘤菌（Bradyrhizobium）形成独特的共生关系，其结瘤过程不依赖于结瘤因子。在这项研究中，我们从山东半岛鸡眼草根瘤中分离到三株革兰氏阴性、杆状的菌株（83002、81013 和 83012），并对它们进行了鉴定。分离株的主要细胞脂肪酸为 C 、C 、C ω7c 11-甲基、特征脂肪酸 3 和特征脂肪酸 8。主要极性脂为磷脂酰乙醇胺（PE）、氨基脂（AL）和磷脂酰胆碱（PC）。基于 16S rRNA 基因座的系统发育分析表明，它们属于慢生根瘤菌属，与模式菌株寡养根瘤菌（Bradyrhizobium oligotrophicum）S58 和脱氮根瘤菌（Bradyrhizobium denitrificans）LMG 8443 的相似度最高。正如预期的那样，对六个看家基因（atpD、recA、glnII、dnaK、gyrB 和 rpoB）和 nifH 基因的串联序列分析表明，这三个菌株在慢生根瘤菌属内形成了一个独特的分支。与最接近的慢生根瘤菌种相比，这三个菌株的平均核苷酸同一性和 DNA-DNA 杂交值最高分别为 87.5%和 65.3%，远低于种的划分阈值，因此证实这三个菌株为一个新种。菌株 83002 的基因组大小为 7.52 Mbp，GC 含量为 65.42 mol%。菌株 83002（=KCTC 82266=MCCC 1K04775）被选为新种的模式菌株，建议将其命名为鸡眼草根瘤菌（Bradyrhizobium aeschynomenes）sp. nov.。
