Coexistence of multiple proteobacterial endosymbionts in the gills of the wood-boring bivalve Lyrodus pedicellatus (Bivalvia: Teredinidae)
Coexistence of multiple proteobacterial endosymbionts in the gills of the wood-boring bivalve Lyrodus pedicellatus (Bivalvia: Teredinidae)
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DOI：
10.1128/aem.68.12.6292-6299.2002
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发表时间：
2002-12-01
影响因子：
4.4
通讯作者：
Morrill, W
中科院分区：
文献类型：
--
作者：
Distel, DL;Beaudoin, DJ;Morrill, W
钻木双壳类的家庭Teredinidae（通常被称为船蛆）是众所周知的窝藏密集群体的革兰氏阴性细菌内专门的细胞（细菌细胞）在他们的鳃。这些共生体被认为提供酶，例如，纤维素酶和二氮酶，它们帮助宿主利用木材作为主要食物来源。一种纤维素分解菌，二氮固定菌，Teredinibacter turnerae，已从许多双壳类的鳃组织中分离出来，并被认为是该双壳类唯一或主要的共生体。在这里，我们证明了一个teredinid物种，Lyrodus pedicellatus，包含至少四个不同的细菌16 S rRNA类型在其鳃细菌细胞，其中之一是相同的T。turnerae。系统发育分析表明，三个新检测到的核糖体类型来自γ-变形菌，它们与T. turnerae。原位杂交与16 S rRNA定向探针表明，共生体核糖体的发生模式内的细菌细胞是可预测的和具体的，与一些细菌细胞含有两个共生体核糖体。然而，只有两个的六个可能的成对组合的四种核糖体被观察到共同出现在同一宿主细胞内。这里提出的结果是一致的存在一个复杂的多重共生在这个船蛆物种。
Wood-boring bivalves of the family Teredinidae (commonly called shipworms) are known to harbor dense populations of gram-negative bacteria within specialized cells (bacteriocytes) in their gills. These symbionts are thought to provide enzymes, e.g., cellulase and dinitrogenase, which assist the host in utilizing wood as a primary food source. A cellulolytic, dinitrogen-fixing bacterium, Teredinibacter turnerae, has been isolated from the gill tissues of numerous teredinid bivalves and has been proposed to constitute the sole or predominant symbiont of this bivalve family. Here we demonstrate that one teredinid species, Lyrodus pedicellatus, contains at least four distinct bacterial 16S rRNA types within its gill bacteriocytes, one of which is identical to that of T. turnerae. Phylogenetic analyses indicate that the three newly detected ribotypes are derived from gamma proteobacteria that are related to but distinct (>6.5% sequence divergence) from T. turnerae. In situ hybridizations with 16S rRNA-directed probes demonstrated that the pattern of occurrence of symbiont ribotypes within bacteriocytes was predictable and specific, with some bacteriocytes containing two symbiont ribotypes. However, only two of the six possible pairwise combinations of the four ribotypes were observed to cooccur within the same host cells. The results presented here are consistent with the existence of a complex multiple symbiosis in this shipworm species.