Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland Australia.
Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland Australia ; Current address: Department of Statistics, University of Illinois Urbana-Champaign, Champaign, IL USA.
Microbiome. 2015 Feb 25;3:5. doi: 10.1186/s40168-015-0067-8. eCollection 2015.
Termites and their microbial gut symbionts are major recyclers of lignocellulosic biomass. This important symbiosis is obligate but relatively open and more complex in comparison to other well-known insect symbioses such as the strict vertical transmission of Buchnera in aphids. The relative roles of vertical inheritance and environmental factors such as diet in shaping the termite gut microbiome are not well understood.
The gut microbiomes of 66 specimens representing seven higher and nine lower termite genera collected in Australia and North America were profiled by small subunit (SSU) rRNA amplicon pyrosequencing. These represent the first reported culture-independent gut microbiome data for three higher termite genera: Tenuirostritermes, Drepanotermes, and Gnathamitermes; and two lower termite genera: Marginitermes and Porotermes. Consistent with previous studies, bacteria comprise the largest fraction of termite gut symbionts, of which 11 phylotypes (6 Treponema, 1 Desulfarculus-like, 1 Desulfovibrio, 1 Anaerovorax-like, 1 Sporobacter-like, and 1 Pirellula-like) were widespread occurring in ≥50% of collected specimens. Archaea are generally considered to comprise only a minority of the termite gut microbiota (<3%); however, archaeal relative abundance was substantially higher and variable in a number of specimens including Macrognathotermes, Coptotermes, Schedorhinotermes, Porotermes, and Mastotermes (representing up to 54% of amplicon reads). A ciliate related to Clevelandella was detected in low abundance in Gnathamitermes indicating that protists were either reacquired after protists loss in higher termites or persisted in low numbers across this transition. Phylogenetic analyses of the bacterial communities indicate that vertical inheritance is the primary force shaping termite gut microbiota. The effect of diet is secondary and appears to influence the relative abundance, but not membership, of the gut communities.
Vertical inheritance is the primary force shaping the termite gut microbiome indicating that species are successfully and faithfully passed from one generation to the next via trophallaxis or coprophagy. Changes in relative abundance can occur on shorter time scales and appear to be an adaptive mechanism for dietary fluctuations.
白蚁及其微生物肠道共生体是木质纤维素生物质的主要回收者。这种重要的共生关系是专性的，但相对开放，并且比其他著名的昆虫共生关系（例如蚜虫中严格的垂直传播 Buchnera）更复杂。垂直遗传和环境因素（如饮食）在塑造白蚁肠道微生物组中的相对作用尚不清楚。
通过小亚基（SSU）rRNA 扩增子焦磷酸测序对来自澳大利亚和北美的 7 个高等和 9 个低等白蚁属的 66 个标本的肠道微生物组进行了分析。这代表了首次报道的三个高等白蚁属的无培养依赖性肠道微生物组数据：Tenuirostritermes、Drepanotermes 和 Gnathamitermes；以及两个低等白蚁属：Marginitermes 和 Porotermes。与先前的研究一致，细菌构成了白蚁肠道共生体的最大部分，其中 11 个菌型（6 个 Treponema、1 个 Desulfarculus 样、1 个 Desulfovibrio、1 个 Anaerovorax 样、1 个 Sporobacter 样和 1 个 Pirellula 样）广泛存在于≥50%的采集标本中。古菌通常被认为只占白蚁肠道微生物组的一小部分（<3%）；然而，在许多标本中，古菌的相对丰度都相当高且变化较大，包括 Macrognathotermes、Coptotermes、Schedorhinotermes、Porotermes 和 Mastotermes（占扩增子读数的高达 54%）。在 Gnathamitermes 中检测到一种与 Clevelandella 相关的纤毛虫，这表明原生动物是在高等白蚁中丢失后重新获得的，或者是在整个过渡过程中以低数量存在的。细菌群落的系统发育分析表明，垂直遗传是塑造白蚁肠道微生物组的主要力量。饮食的影响是次要的，似乎影响肠道群落的相对丰度，但不影响成员组成。
垂直遗传是塑造白蚁肠道微生物组的主要力量，这表明物种通过营养交换或排粪成功且忠实地从一代传递到下一代。相对丰度的变化可能发生在更短的时间尺度上，并且似乎是对饮食波动的一种适应机制。
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