Bacteroidales ectosymbionts of gut flagellates shape the nitrogen-fixing community in dry-wood termites
Bacteroidales ectosymbionts of gut flagellates shape the nitrogen-fixing community in dry-wood termites
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DOI：
10.1038/ismej.2011.194
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发表时间：
2012-07-01
期刊：
影响因子：
11
通讯作者：
Brune, Andreas
中科院分区：
文献类型：
--
作者：
Desai, Mahesh S.;Brune, Andreas
虽然有充分的证据表明，食木白蚁饮食中氮的缺乏可以通过其肠道微生物群的固氮能力来补偿，但负责这种活动的细菌在很大程度上是未知的。在这里，我们分析了固氮酶基因的多样性和表达（同源物nifH）在四种干木材白蚁（Kalotermitidae），这茁壮成长的一个特别是氮贫资源。虽然每个物种在其微升大小的后肠中都有一套高度多样的白蚁特异性同源物，但只有一个核心组与密螺旋体和Azoarcus spp.的nifH基因相关，固氮类杆菌pseudotrichonymphae '，第一个被确定为固氮菌的拟杆菌目的成员，和白蚁肠道特异性anfH基因的迄今未知的起源优先表达。转录模式证实，白蚁属之间的活性固氮菌的人口根本不同。毛细管采摘悬浮液的鞭毛虫阿尔塔和Snyderella tabogae揭示，他们的细菌外共生体各自具有两个旁系同源的nifH，这显然已经收购连续进化过程中的拟杆菌目，但只有其中之一（anfH）是积极表达。转录模式既不与饮食中的钼含量相关，也不与微传感器测量的肠道氢浓度相关。我们建议，固氮社区在不同的干木材白蚁是由其特定的鞭毛虫种群的共生体。我们的研究结果表明，重氮营养性质的Armantifilum devescovinae'有一个重要的作用，在干木材白蚁的氮代谢，是协同进化的驱动力，其鞭毛虫宿主。The ISME Journal（2012）6，1302-1313; doi：10.1038/ismej.2011.194; 2011年12月22日在线发表
Although it is well documented that the lack of nitrogen in the diet of wood-feeding termites is compensated by the nitrogen-fixing capacity of their gut microbiota, the bacteria responsible for this activity are largely unknown. Here, we analyzed the diversity and expression of nitrogenase genes (homologs of nifH) in four species of dry-wood termites (Kalotermitidae), which thrive on a particularly nitrogen-poor resource. Although each species harbored a highly diverse suite of termite-specific homologs in their microliter-sized hindgut, only a core set related to nifH genes of Treponema and Azoarcus spp., 'Azobacteroides pseudotrichonymphae', the first member of the Bacteroidales identified as a diazotroph, and termite-gut-specific anfH genes of hitherto unknown origin were preferentially expressed. Transcription patterns corroborated that the populations of active diazotrophs differ fundamentally between termite genera. Capillary-picked suspensions of the flagellates Devescovina arta and Snyderella tabogae revealed that their bacterial ectosymbionts each possess two paralogs of nifH, which apparently have been acquired consecutively during evolution of Bacteroidales, but only one of them (anfH) is actively expressed. Transcription patterns correlated neither with the molybdenum content of the diet nor with intestinal hydrogen concentrations, measured with microsensors. We propose that the nitrogen-fixing community in different dry-wood termites is shaped by the symbionts of their specific flagellate populations. Our findings suggest that the diazotrophic nature of 'Armantifilum devescovinae' has an important role in the nitrogen metabolism of dry-wood termites and is the driving force of co-evolution with its flagellate host. The ISME Journal (2012) 6, 1302-1313; doi:10.1038/ismej.2011.194; published online 22 December 2011