RAST annotation.

Symbiotic relationships are ubiquitous throughout the world’s oceans, yet for many marine organisms, including those in the high latitudes, little is understood about symbiotic associations and functional relationships. From a recently determined genome sequence of a filter-feeding basket star from Argentina, Gorgonocephalus chilensis, we discovered a novel Mycoplasma species with a 796Kb genome (CheckM completeness of 97.9%, G+C content = 30.1%). Similar to other Mycoplasma spp. within Mycoplasmatota, genomic analysis of the novel organism revealed reduced metabolic pathways including incomplete biosynthetic pathways, suggesting an obligate association with their basket star host. Results of 16S rRNA and multi-locus phylogenetic analyses revealed that this organism belonged to a recently characterized non-free-living lineage of Mycoplasma spp. specifically associated with marine invertebrate animals. Thus, the name “Candidatus Mycoplasma mahonii” is proposed for this novel species. Based on 16S rRNA PCR-screening, we found that Ca. M. mahonii also occurs in Gorgonocephalus eucnemis from the Northwest Pacific and other Gorgonocephalus chilensis from Argentinian waters. The level of sequence conservation within Ca. M. mahonii is considerable between widely disparate high-latitude Gorgonocephalus species, suggesting that oceanic dispersal of this microbe may be greater than excepted.共生关系在全球海洋中无处不在，但对于包括高纬度海域生物在内的诸多海洋生物而言，学界对其共生关联与功能关系的认知仍十分有限。本研究从阿根廷产滤食性智利筐蛇尾（Gorgonocephalus chilensis）的新近解析基因组序列中，发现了一种基因组大小为796kb的新型支原体属（Mycoplasma）物种，其CheckM完整性达97.9%，G+C含量为30.1%。与柔膜菌门（Mycoplasmatota）内其他支原体属物种类似，对该新物种的基因组分析显示其代谢通路存在缩减，包括生物合成通路不全，这提示它与筐蛇尾宿主存在专性共生关系。16S核糖体RNA（16S rRNA）及多基因座系统发育分析结果显示，该物种隶属于新近被表征的、专性与海洋无脊椎动物共生的非自由生活支原体支系。因此，本研究将该新物种命名为‘候选Mahon支原体（Candidatus Mycoplasma mahonii）’。基于16S rRNA聚合酶链式反应（PCR）筛查结果，我们发现候选Mahon支原体（Ca. M. mahonii）同样存在于西北太平洋的真丛筐蛇尾（Gorgonocephalus eucnemis）以及阿根廷海域的其他智利筐蛇尾体内。在亲缘关系相距甚远的不同高纬度筐蛇尾物种体内，候选Mahon支原体的序列保守性仍较高，这提示该微生物的海洋传播范围可能远超此前预期。