Aijaz Iqbal, Koudelka Gerald B
FEMS Microbiol Ecol. 2017 Apr 1;93(4). doi: 10.1093/femsec/fix030.
The microbial communities in natural environments such as soil, pond water, or animal rumens are composed of a diverse mixture of bacteria and protozoa including ciliates or flagellates. In such microbiomes, a major source of bacterial mortality is grazing by phagocytic protists. Many protists are omnivorous heterotrophs, feeding on a range of different bacterial species. Due to this indiscriminate feeding, different bacterial species can assemble together in the same phagocytic vesicles where they can potentially exchange genetic material. Here we show that Tetrahymena thermophila imports and accumulates phage donor and recipient bacterial strains in its phagocytic vesicles and that under laboratory conditions the ingested bacteria remain viable for ≥2 h. Prophages in the ingested bacteria induce immediately after ingestion, and the released phages are concentrated in the phagocytic vesicles of the ciliate. These phages retain their ability to infect phage-susceptible bacterial strains. As a consequence of being confined within the phagosome, the frequency of lysogen formation in these vesicles increases 6-fold as compared with the bulk solution. Collectively, these observations suggest that T. thermophila aids in dissemination of bacteriophages by accumulating susceptible bacteria and phages in their phagocytic vesicles.
自然环境中的微生物群落，如土壤、池塘水或动物瘤胃中的微生物群落，是由细菌和原生动物的多种混合物组成的，包括纤毛虫或鞭毛虫。在这样的微生物群落中，细菌死亡的一个主要来源是吞噬性原生生物的捕食。许多原生生物是杂食性异养生物，以一系列不同的细菌种类为食。由于这种不加区分的摄食，不同的细菌种类可以聚集在同一个吞噬小泡中，在那里它们可能会交换遗传物质。在这里，我们表明嗜热四膜虫在其吞噬小泡中摄取并积累噬菌体供体和受体细菌菌株，并且在实验室条件下，摄入的细菌在≥2小时内保持存活。摄入细菌中的原噬菌体在摄入后立即诱导，释放的噬菌体集中在纤毛虫的吞噬小泡中。这些噬菌体保留了感染噬菌体敏感细菌菌株的能力。由于被限制在吞噬体内，这些小泡中溶原形成的频率与大量溶液相比增加了6倍。总的来说，这些观察结果表明嗜热四膜虫通过在其吞噬小泡中积累易感细菌和噬菌体来帮助噬菌体传播。
