Protist-Bacteria Associations: Gammaproteobacteria and Alphaproteobacteria Are Prevalent as Digestion-Resistant Bacteria in Ciliated Protozoa.
Protist-Bacteria Associations: Gammaproteobacteria and Alphaproteobacteria Are Prevalent as Digestion-Resistant Bacteria in Ciliated Protozoa.
复制标题
DOI：
10.3389/fmicb.2016.00498
复制
发表时间：
2016
影响因子：
5.2
通讯作者：
Zhang Q
中科院分区：
文献类型：
--
作者：
Gong J;Qing Y;Zou S;Fu R;Su L;Zhang X;Zhang Q
原生生物噬菌作用是一个涉及摄食和消化的微生物过程，在水生和陆生生态系统的微生物环中具有重要的生态意义。虽然细菌对原生生物素摄入的抗性已经相对较好地了解，但对原生生物素消化知之甚少，其中一些摄入的细菌不能在自然环境中的主要原生生物素食草动物的细胞中消化。在这里，我们报告的消化抗性细菌（DRB），可以生存饥饿和形成相对稳定的协会与11个海洋和淡水纤毛虫物种的系统发育身份。利用克隆文库和16 S rRNA基因测序，我们发现原生生物捕食者可以宿主高度多样性的DRB，其中大部分代表尚未被培养的新细菌类群。利用荧光原位杂交技术检测了这些细菌在宿主细胞内的定位、数量和活力。DRB隶属于放线菌门、拟杆菌门、厚壁菌门、Parcubacteria（OD 1）、浮游菌门和变形菌门，其中γ变形菌门和α变形菌门是最常见的类别。γ-和α-变形菌的优势很好地对应于先前的全球海洋采样宏基因组数据的研究，显示了这两个分类群中广泛存在的细菌VI型和IV型分泌系统（T6 SS和T4 SS），这表明分泌系统在促进海洋原生生物-细菌协会中具有重要作用。在DRB组合中，交替单胞菌科（Alteromonadaceae）、假交替单胞菌科（Pseudoalteromonadaceae）和弧菌科（Vibrionaceae）等机会性细菌的比例较高，表明这些细菌可以逃避原生生物的放牧，从而在群落中持续存在和积累，但这与它们在自然界中的罕见性形成鲜明对比。这就引出了一个问题，即病毒裂解在杀死微生物群落中的这些不可消化的细菌方面是否有意义。总而言之，我们对DRB身份的研究为微生物相互作用提供了新的线索，并产生了进一步的假设，包括细菌蛋白分泌系统在构建细菌群落组成和水生环境中“微生物黑匣子”功能方面的潜在重要性。
Protistan bacterivory, a microbial process involving ingestion and digestion, is ecologically important in the microbial loop in aquatic and terrestrial ecosystems. While bacterial resistance to protistan ingestion has been relatively well understood, little is known about protistan digestion in which some ingested bacteria could not be digested in cells of major protistan grazers in the natural environment. Here we report the phylogenetic identities of digestion-resistant bacteria (DRB) that could survive starvation and form relatively stable associations with 11 marine and one freshwater ciliate species. Using clone library and sequencing of 16S rRNA genes, we found that the protistan predators could host a high diversity of DRB, most of which represented novel bacterial taxa that have not been cultivated. The localization inside host cells, quantity, and viability of these bacteria were checked using fluorescence in situ hybridization. The DRB were affiliated with Actinobacteria, Bacteroidetes, Firmicutes, Parcubacteria (OD1), Planctomycetes, and Proteobacteria, with Gammaproteobacteria and Alphaproteobacteria being the most frequently occurring classes. The dominance of Gamma- and Alphaproteobacteria corresponds well to a previous study of Global Ocean Sampling metagenomic data showing the widespread types of bacterial type VI and IV secretion systems (T6SS and T4SS) in these two taxa, suggesting a putatively significant role of secretion systems in promoting marine protist-bacteria associations. In the DRB assemblages, opportunistic bacteria such as Alteromonadaceae, Pseudoalteromonadaceae, and Vibrionaceae often presented with high proportions, indicating these bacteria could evade protistan grazing thus persist and accumulate in the community, which, however, contrasts with their well-known rarity in nature. This begs the question whether viral lysis is significant in killing these indigestible bacteria in microbial communities. Taken together, our study on the identity of DRB sheds new light on microbial interactions and generates further hypotheses including the potential importance of bacterial protein secretion systems in structuring bacterial community composition and functioning of “microbial black box” in aquatic environments.