Department of Biology, Drexel University, Philadelphia, PA 19104, USA.
Mol Ecol. 2012 Jul;21(13):3363-78. doi: 10.1111/j.1365-294X.2012.05552.x. Epub 2012 Apr 4.
Symbiotic bacteria often help their hosts acquire nutrients from their diet, showing trends of co-evolution and independent acquisition by hosts from the same trophic levels. While these trends hint at important roles for biotic factors, the effects of the abiotic environment on symbiotic community composition remain comparably understudied. In this investigation, we examined the influence of abiotic and biotic factors on the gut bacterial communities of fish from different taxa, trophic levels and habitats. Phylogenetic and statistical analyses of 25 16S rRNA libraries revealed that salinity, trophic level and possibly host phylogeny shape the composition of fish gut bacteria. When analysed alongside bacterial communities from other environments, fish gut communities typically clustered with gut communities from mammals and insects. Similar consideration of individual phylotypes (vs. communities) revealed evolutionary ties between fish gut microbes and symbionts of animals, as many of the bacteria from the guts of herbivorous fish were closely related to those from mammals. Our results indicate that fish harbour more specialized gut communities than previously recognized. They also highlight a trend of convergent acquisition of similar bacterial communities by fish and mammals, raising the possibility that fish were the first to evolve symbioses resembling those found among extant gut fermenting mammals.
共生细菌通常帮助它们的宿主从饮食中获取营养，表现出宿主与同一营养级别的共生细菌共同进化和独立获取的趋势。虽然这些趋势暗示了生物因素的重要作用，但生物因素对共生群落组成的影响仍相对研究不足。在这项研究中，我们研究了非生物和生物因素对来自不同分类群、营养级和栖息地的鱼类肠道细菌群落的影响。对 25 个 16S rRNA 文库的系统发育和统计分析表明，盐度、营养级和可能的宿主进化史影响着鱼类肠道细菌的组成。当与其他环境中的细菌群落一起分析时，鱼类肠道群落通常与哺乳动物和昆虫的肠道群落聚类。对单个分类群（与群落相对）的类似考虑表明，鱼类肠道微生物与动物的共生体之间存在进化联系，因为许多草食性鱼类肠道中的细菌与哺乳动物的细菌密切相关。我们的研究结果表明，鱼类拥有比以前认为的更具特异性的肠道群落。它们还突出了鱼类和哺乳动物趋同获取相似细菌群落的趋势，这增加了鱼类首先进化出类似于现存肠道发酵哺乳动物的共生关系的可能性。
