Schizasterid Heart Urchins Host Microorganisms in a Digestive Symbiosis of Mesozoic Origin
Schizasterid Heart Urchins Host Microorganisms in a Digestive Symbiosis of Mesozoic Origin
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DOI：
10.3389/fmicb.2020.01697
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发表时间：
2020-07
影响因子：
5.2
通讯作者：
A. Ziegler;A. Gilligan;J. Dillon;B. Pernet
中科院分区：
文献类型：
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作者：
A. Ziegler;A. Gilligan;J. Dillon;B. Pernet
由于它们的生活方式、数量和摄食习惯，底栖海洋存款饲养者对洋底有重大影响。由于这些动物也摄取与其沉积物和海水饮食有关的微生物，它们的消化道通常含有各种细菌。然而，虽然这些微生物中的大多数是瞬时的，但有些可能成为常驻肠道微生物组的一部分，特别是当在专门的肠道隔室中避开主要的肠道菌群时。在这里，我们提供了一个深入的分析的结构和内容物的肠盲肠（IC），后肠憩室中发现的唯一的心脏海胆（Echinoidea：Spatangoida：Schizophrenidae）。基于标本的townsendi，除了各种其他的townsendi类群，我们的结构表征的IC表明，该器官是一个高度专业化的肠道隔间具有独特的结构特性。下一代测序显示IC含有主要由拟杆菌目、脱硫杆菌目和螺旋体目组成的微生物群体。该肠道区室的微生物组在组成上显著不同，并且在多样性上低于沉积物填充的主消化道中的微生物种群。对IC及其微生物组的功能和进化的推断表明，这种共生在宿主营养中起着独特的作用，并且它至少在6600万年前的中生代最后阶段进化。
Because of their lifestyles, abundance, and feeding habits, infaunal marine deposit feeders have a significant impact on the ocean floor. As these animals also ingest microorganisms associated with their sediment and seawater diet, their digestive tract usually contains a diverse array of bacteria. However, while most of these microorganisms are transients, some may become part of a resident gut microbiome, in particular when sheltered from the main flow of digesta in specialized gut compartments. Here, we provide an in-depth analysis of the structure and contents of the intestinal caecum (IC), a hindgut diverticulum found exclusively in schizasterid heart urchins (Echinoidea: Spatangoida: Schizasteridae). Based on specimens of Brisaster townsendi, in addition to various other schizasterid taxa, our structural characterization of the IC shows that the organ is a highly specialized gut compartment with unique structural properties. Next generation sequencing shows that the IC contains a microbial population composed predominantly of Bacteroidales, Desulfobacterales, and Spirochaetales. The microbiome of this gut compartment is significantly different in composition and lower in diversity than the microbial population in the sediment-filled main digestive tract. Inferences on the function and evolution of the IC and its microbiome suggest that this symbiosis plays a distinct role in host nutrition and that it evolved at least 66 million years ago during the final phase of the Mesozoic.