<i>Rivularia halophila</i> sp. nov. (Nostocales, Cyanobacteria): the first species of <i>Rivularia</i> described with the modern polyphasic approach

Natural populations of a <i>Rivularia</i>-like cyanobacterium were collected from the carbonate deposits of the temporarily flooded littoral zone of a hypersaline, high elevation lake, The Laguna Negra, Andes, Argentina. Subsequently, the cyanobacterial strain PUNA-NP3, named after its origin (Puna Volcanic Plateau) was isolated from these <i>Rivularia</i>-like rounded, pillow-like, black microbial mats. None of the previously described species of the genus <i>Rivularia</i> occupy inland, hypersaline aquatic environments. After morphological examination of this strain, we found clear morphological autapomorphies, such as mucilaginous pads at the bases of the young trichomes, wide trichomes and filaments, and uniquely branched trichomes. Furthermore, based on results from 16S rRNA phylogeny and analysis of the 16S-23S ITS region, PUNA-NP3 was found to be an independent lineage of the evolutionary tree. Based on the combination of ecological, morphological and molecular evidence, we name strain PUNA-NP3 <i>Rivularia halophila</i> sp. nov. a new species under requirements of the International Code of Nomenclature for Algae, Fungi and Plants.研究团队从阿根廷安第斯山脉高盐高海拔湖泊内格拉湖（Laguna Negra）的临时淹没沿岸带碳酸盐沉积样本中，采集到一类形似胶须藻属（Rivularia）的蓝细菌自然种群。随后，研究人员从这些呈圆形、枕状的黑色胶须藻样微生物垫中，分离得到蓝细菌菌株PUNA-NP3，该菌株以其分离来源地普纳火山高原（Puna Volcanic Plateau）命名。此前已描述的胶须藻属（Rivularia）物种均未分布于内陆高盐水生环境中。对该菌株开展形态学检查后，研究人员发现其具有明确的形态特有衍征：幼藻丝基部具粘液垫、藻丝与丝状体宽大，且具有独特分枝的藻丝。此外，基于16S rRNA系统发育分析及16S-23S内转录间隔区（ITS）序列分析结果，菌株PUNA-NP3被确定为系统发育树中的一个独立演化支。综合生态学、形态学与分子生物学证据，依据《国际藻类、真菌和植物命名法规》的相关要求，我们将菌株PUNA-NP3命名为嗜盐胶须藻（Rivularia halophila）sp. nov.，为一新种。