Phithakrotchanakoon Chitwadee, Kitikhun Supattra, Siriarchawatana Paopit, Charoenyingcharoen Piyanat, Jeennor Sukanya, Nilsakha Thanyakorn, Chanpet Amonwan, Vorajinda Thanat, Mayteeworakoon Sermsiri, Yukphan Pattaraporn, Ingsriswang Supawadee
Thailand Bioresource Research Center (TBRC), National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand.
Functional Ingredients and Food Innovation Research Group (IFIG), National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand.
Int J Syst Evol Microbiol. 2025 Jun;75(6). doi: 10.1099/ijsem.0.006815.
Two Gram-stain-negative, aerobic, non-motile, non-gliding, rod-shaped bacterial strains, designated as TBRC 19031 and TBRC 19032, were isolated from water samples collected from the Mekong River, Thailand. Strain TBRC 19031 was obtained from Chiang Saen in the upstream section near the borders with China and Myanmar, while TBRC 19032 originated from Khong Chiam, in the downstream section where the river exits Thailand. Colonies of both strains were circular, smooth and deep yellow on Reasoner's 2A agar and did not produce flexirubin-type pigments. Phylogenetic analysis with 16S rRNA gene sequences placed both strains within the genus , showing the highest sequence similarity to ARSA-15 (98.29% for TBRC 19031 and 98.22% for TBRC 19032). However, whole-genome comparisons between the strains and ARSA-15 revealed average nt identity (89.39% and 89.29%), average aa identity (92.84% and 92.95%) and digital DNA-DNA hybridization (35.00% and 34.70%). The predominant fatty acids were iso-C, iso-C and iso-C 3-OH, and menaquinone MK-6 was the major respiratory quinone. The major polar lipids of both strains included phosphatidylethanolamine, steryl ester and diacylglycerol. The genome sizes were 3.02 and 3.04 Mbp, with G+C contents of 38.3% and 38.2% for TBRC 19031 and TBRC 19032, respectively. Comparative genomic analyses revealed the absence of genes involved in sulphate reduction and denitrification pathways and the presence of a gene encoding phosphatidylinositol synthase, distinguishing them from other within the clade. Ecological profiling using public metagenomic datasets showed that both strains were associated with lotic freshwater environments. This study not only introduces sp. nov. as a new species but also provides broader insights into the ecology, metabolism and environmental distribution of freshwater . The genomic features identified here offer promising leads for future studies in microbial ecology, comparative genomics and functional gene mining in aquatic ecosystems. The type strain is TBRC 19031 (TBRC 19031=NBRC 117006).
从泰国湄公河采集的水样中分离出两株革兰氏阴性、需氧、无运动性、无滑行能力的杆状细菌菌株，分别命名为TBRC 19031和TBRC 19032。菌株TBRC 19031取自与中国和缅甸接壤的上游清盛地区，而TBRC 19032则源自河流流出泰国的下游孔敬地区。两株菌株在Reasoner's 2A琼脂上的菌落均为圆形、光滑且呈深黄色，不产生类flexirubin型色素。基于16S rRNA基因序列的系统发育分析将两株菌株置于该属内，与ARSA-15的序列相似性最高（TBRC 19031为98.29%，TBRC 19032为98.22%）。然而，菌株与ARSA-15之间的全基因组比较显示平均核苷酸同一性（分别为89.39%和89.29%）、平均氨基酸同一性（分别为92.84%和92.95%）以及数字DNA-DNA杂交率（分别为35.00%和34.70%）。主要脂肪酸为异-C、异-C和异-C 3-OH，甲基萘醌MK-6是主要的呼吸醌。两株菌株的主要极性脂质包括磷脂酰乙醇胺、甾醇酯和二酰甘油。基因组大小分别为3.02和3.04 Mbp，TBRC 19031和TBRC
19032的G+C含量分别为38.3%和38.2%。比较基因组分析表明，它们缺乏参与硫酸盐还原和反硝化途径的基因，且存在一个编码磷脂酰肌醇合酶的基因，这使其与该进化枝内的其他物种区分开来。使用公共宏基因组数据集进行的生态分析表明，两株菌株均与流水淡水环境相关。本研究不仅引入了新物种，还为淡水的生态、代谢和环境分布提供了更广泛的见解。这里确定的基因组特征为未来在水生生态系统中的微生物生态学、比较基因组学和功能基因挖掘研究提供了有前景的线索。模式菌株为TBRC 19031（TBRC 19031=NBRC 117006）。
