Loudon Andrew H, Venkataraman Arvind, Van Treuren William, Woodhams Douglas C, Parfrey Laura Wegener, McKenzie Valerie J, Knight Rob, Schmidt Thomas M, Harris Reid N
Department of Biology, James Madison University, Harrisonburg VA, USA.
Department of Internal Medicine, University of Michigan, Ann Arbor MI, USA.
Front Microbiol. 2016 Mar 16;7:333. doi: 10.3389/fmicb.2016.00333. eCollection 2016.
Skin bacterial communities can protect amphibians from a fungal pathogen; however, little is known about how these communities are maintained. We used a neutral model of community ecology to identify bacteria that are maintained on salamanders by selection or by dispersal from a bacterial reservoir (soil) and ecological drift. We found that 75% (9/12) of bacteria that were consistent with positive selection, <1% of bacteria that were consistent with random dispersal and none of the bacteria that were consistent under negative selection had a 97% or greater match to antifungal isolates. Additionally we performed an experiment where salamanders were either provided or denied a bacterial reservoir and estimated immigration and loss (emigration and local extinction) rates of bacteria on salamanders in both treatments. Loss was strongly related to bacterial richness, suggesting competition is important for structuring the community. Bacteria closely related to antifungal isolates were more likely to persist on salamanders with or without a bacterial reservoir, suggesting they had a competitive advantage. Furthermore, over-represented and under-represented operational taxonomic units (OTUs) had similar persistence on salamanders when a bacterial reservoir was present. However, under-represented OTUs were less likely to persist in the absence of a bacterial reservoir, suggesting that the over-represented and under-represented bacteria were selected against or for on salamanders through time. Our findings from the neutral model, migration and persistence analyses show that bacteria that exhibit a high similarity to antifungal isolates persist on salamanders, which likely protect hosts against pathogens and improve fitness. This research is one of the first to apply ecological theory to investigate assembly of host associated-bacterial communities, which can provide insights for probiotic bioaugmentation as a conservation strategy against disease.
皮肤细菌群落可以保护两栖动物免受真菌病原体的侵害；然而，对于这些群落是如何维持的，我们却知之甚少。我们使用群落生态学的中性模型来识别通过选择或从细菌库（土壤）扩散以及生态漂变而在蝾螈身上维持的细菌。我们发现，与正向选择一致的细菌中有75%（9/12）、与随机扩散一致的细菌中不到1%，以及与负向选择一致的细菌中没有一种与抗真菌分离株的匹配度达到97%或更高。此外，我们进行了一项实验，给蝾螈提供或不提供细菌库，并估计两种处理中蝾螈身上细菌的迁入和损失（迁出和局部灭绝）率。损失与细菌丰富度密切相关，这表明竞争对于构建群落很重要。与抗真菌分离株密切相关的细菌在有或没有细菌库的蝾螈身上更有可能持续存在，这表明它们具有竞争优势。此外，当存在细菌库时，优势和劣势的操作分类单元（OTU）在蝾螈身上具有相似的持久性。然而，在没有细菌库的情况下，劣势OTU持续存在的可能性较小，这表明随着时间的推移，优势和劣势细菌在蝾螈身上受到正向或负向选择。我们从中性模型、迁移和持久性分析中得到的结果表明，与抗真菌分离株具有高度相似性的细菌在蝾螈身上持续存在，这可能保护宿主免受病原体侵害并提高适应性。这项研究是最早应用生态学理论来研究宿主相关细菌群落组装的研究之一，可为益生菌生物强化作为一种疾病防治保护策略提供见解。
