Exploring the Potential for Actinobacteria as Defensive Symbionts in Fungus-Growing Termites
Exploring the Potential for Actinobacteria as Defensive Symbionts in Fungus-Growing Termites
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DOI：
10.1007/s00248-011-9987-4
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发表时间：
2012-05-01
影响因子：
3.6
通讯作者：
Poulsen, Michael
中科院分区：
文献类型：
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作者：
Visser, Anna A.;Nobre, Tania;Poulsen, Michael
在真菌生长的白蚁中，假木霉亚属的真菌通过与白蚁真菌（Termitomyces）的底物竞争来威胁群体健康。白蚁抑制假木霉的潜在机制仍不清楚。在这里，我们探讨放线菌是否可能作为真菌生长白蚁中的假木霉的防御共生体发挥作用。我们从 30 个生长真菌的白蚁群落中采集了放线菌样本，这些白蚁群落涵盖三个主要白蚁属和两个地理位置较远的地点。我们的分离产生了 360 个放线菌，从中我们选择了子集进行形态学（288 个分离株，分为 44 种形态型）和 16S rRNA（35 个分离株，涵盖大多数形态型）表征。在所有采样的巢穴和群体部分中都发现了放线菌，并且从系统发育角度来看，它们散布着来自真菌生长白蚁以外来源的放线菌，表明缺乏特异性。对 288 个分离株针对真菌品种和竞争对手的抗生素活性筛选表明，大多数放线菌产生的分子具有抗真菌活性。为了测试抗生素的特异性，对 53 个分离株进行了更详细的生物测定，结果表明许多放线菌同时抑制假木霉和鸡蚁，并且栽培真菌通常比竞争对手更容易受到抑制。这表明防御性共生体要么不存在于系统中，要么它们（如果存在）代表了孤立群落的一个子集。如果是这样，则必须有针对性地使用抗生素，由白蚁将其施用于特定区域。我们描述了在真菌生长的白蚁巢中首次发现的产生抗生素的放线菌的集合。然而，由于发现的多样性，以及缺乏系统发育和生物活性特异性，需要进一步的工作来更好地理解产生抗生素的细菌在真菌生长的白蚁互利系统中的假定作用。
In fungus-growing termites, fungi of the subgenus Pseudoxylaria threaten colony health through substrate competition with the termite fungus (Termitomyces). The potential mechanisms with which termites suppress Pseudoxylaria have remained unknown. Here we explore if Actinobacteria potentially play a role as defensive symbionts against Pseudoxylaria in fungus-growing termites. We sampled for Actinobacteria from 30 fungus-growing termite colonies, spanning the three main termite genera and two geographically distant sites. Our isolations yielded 360 Actinobacteria, from which we selected subsets for morphological (288 isolates, grouped in 44 morphotypes) and for 16S rRNA (35 isolates, spanning the majority of morphotypes) characterisation. Actinobacteria were found throughout all sampled nests and colony parts and, phylogenetically, they are interspersed with Actinobacteria from origins other than fungus-growing termites, indicating lack of specificity. Antibiotic-activity screening of 288 isolates against the fungal cultivar and competitor revealed that most of the Actinobacteria-produced molecules with antifungal activity. A more detailed bioassay on 53 isolates, to test the specificity of antibiotics, showed that many Actinobacteria inhibit both Pseudoxylaria and Termitomyces, and that the cultivar fungus generally is more susceptible to inhibition than the competitor. This suggests that either defensive symbionts are not present in the system or that they, if present, represent a subset of the community isolated. If so, the antibiotics must be used in a targeted fashion, being applied to specific areas by the termites. We describe the first discovery of an assembly of antibiotic-producing Actinobacteria occurring in fungus-growing termite nests. However, due to the diversity found, and the lack of both phylogenetic and bioactivity specificity, further work is necessary for a better understanding of the putative role of antibiotic-producing bacteria in the fungus-growing termite mutualistic system.