Del Campo Javier, Heger Thierry J, Rodríguez-Martínez Raquel, Worden Alexandra Z, Richards Thomas A, Massana Ramon, Keeling Patrick J
Department of Botany, University of British Columbia, Vancouver, BC, Canada.
Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, United States.
Front Microbiol. 2019 Oct 23;10:2373. doi: 10.3389/fmicb.2019.02373. eCollection 2019.
Apicomplexans are a group of microbial eukaryotes that contain some of the most well-studied parasites, including the causing agents of toxoplasmosis and malaria, and emergent diseases like cryptosporidiosis or babesiosis. Decades of research have illuminated the pathogenic mechanisms, molecular biology, and genomics of model apicomplexans, but we know little about their diversity and distribution in natural environments. In this study we analyze the distribution of apicomplexans across a range of both host-associated and free-living environments. Using publicly available small subunit (SSU) rRNA gene databases, high-throughput environmental sequencing (HTES) surveys, and our own generated HTES data, we developed an apicomplexan reference database, which includes the largest apicomplexan SSU rRNA tree available to date and encompasses comprehensive sampling of this group and their closest relatives. This tree allowed us to identify and correct incongruences in the molecular identification of apicomplexan sequences. Analyzing the diversity and distribution of apicomplexans in HTES studies with this curated reference database also showed a widespread, and quantitatively important, presence of apicomplexans across a variety of free-living environments. These data allow us to describe a remarkable molecular diversity of this group compared with our current knowledge, especially when compared with that identified from described apicomplexan species. This is most striking in marine environments, where potentially the most diverse apicomplexans apparently exist, but have not yet been formally recognized. The new database will be useful for microbial ecology and epidemiological studies, and provide valuable reference for medical and veterinary diagnosis especially in cases of emerging, zoonotic, and cryptic infections.
顶复门生物是一类微生物真核生物，其中包含一些研究最为深入的寄生虫，包括弓形虫病和疟疾的病原体，以及隐孢子虫病或巴贝斯虫病等新出现的疾病。数十年的研究揭示了典型顶复门生物的致病机制、分子生物学和基因组学，但我们对它们在自然环境中的多样性和分布却知之甚少。在本研究中，我们分析了顶复门生物在一系列宿主相关和自由生活环境中的分布情况。利用公开可用的小亚基（SSU）rRNA基因数据库、高通量环境测序（HTES）调查以及我们自己生成的HTES数据，我们开发了一个顶复门生物参考数据库，其中包括迄今为止最大的顶复门生物SSU rRNA树，涵盖了该类群及其近亲的全面采样。这棵树使我们能够识别并纠正顶复门生物序列分子鉴定中的不一致之处。使用这个经过整理的参考数据库分析HTES研究中顶复门生物的多样性和分布情况，也显示出顶复门生物在各种自由生活环境中广泛存在且数量可观。与我们目前的认知相比，这些数据使我们能够描述该类群显著的分子多样性，特别是与从已描述的顶复门生物物种中鉴定出的情况相比。这在海洋环境中最为显著，在那里可能存在最多样化的顶复门生物，但尚未得到正式确认。这个新数据库将有助于微生物生态学和流行病学研究，并为医学和兽医诊断提供有价值的参考，特别是在新出现的、人畜共患的和隐性感染的情况下。
