Department of Immunology and The Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Proc Natl Acad Sci U S A. 2012 Oct 23;109(43):17621-6. doi: 10.1073/pnas.1206136109. Epub 2012 Oct 8.
The mammalian intestine is home to a dense community of bacteria and its associated bacteriophage (phage). Virtually nothing is known about how phages impact the establishment and maintenance of resident bacterial communities in the intestine. Here, we examine the phages harbored by Enterococcus faecalis, a commensal of the human intestine. We show that E. faecalis strain V583 produces a composite phage (ΦV1/7) derived from two distinct chromosomally encoded prophage elements. One prophage, prophage 1 (ΦV1), encodes the structural genes necessary for phage particle production. Another prophage, prophage 7 (ΦV7), is required for phage infection of susceptible host bacteria. Production of ΦV1/7 is controlled, in part, by nutrient availability, because ΦV1/7 particle numbers are elevated by free amino acids in culture and during growth in the mouse intestine. ΦV1/7 confers an advantage to E. faecalis V583 during competition with other E. faecalis strains in vitro and in vivo. Thus, we propose that E. faecalis V583 uses phage particles to establish and maintain dominance of its intestinal niche in the presence of closely related competing strains. Our findings indicate that bacteriophages can impact the dynamics of bacterial colonization in the mammalian intestinal ecosystem.
哺乳动物肠道中栖息着密集的细菌群落及其相关噬菌体（噬菌体）。实际上，人们对噬菌体如何影响肠道中常驻细菌群落的建立和维持知之甚少。在这里，我们研究了肠球菌（Enterococcus faecalis）中携带的噬菌体，肠球菌是人类肠道的共生菌。我们表明，粪肠球菌菌株 V583 产生一种复合噬菌体（ΦV1/7），来源于两个不同的染色体编码的前噬菌体元件。一个前噬菌体，前噬菌体 1（ΦV1），编码噬菌体颗粒产生所必需的结构基因。另一个前噬菌体，前噬菌体 7（ΦV7），是噬菌体感染易感宿主细菌所必需的。ΦV1/7 的产生部分受到营养物质可用性的控制，因为在培养物中和在小鼠肠道中生长时，游离氨基酸会增加 ΦV1/7 颗粒的数量。在体外和体内与其他粪肠球菌菌株竞争时，ΦV1/7 赋予了 V583 粪肠球菌优势。因此，我们提出粪肠球菌 V583 利用噬菌体颗粒在存在密切相关的竞争菌株的情况下建立和维持其肠道生态位的优势。我们的发现表明，噬菌体可以影响哺乳动物肠道生态系统中细菌定植的动态。
