Graf J, Ruby E G
Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.
Proc Natl Acad Sci U S A. 1998 Feb 17;95(4):1818-22. doi: 10.1073/pnas.95.4.1818.
Animals are typically colonized by diverse bacterial symbionts, many of which are commensal and, in numerous cases, even essential for their host's proper development and growth. In exchange, the host must supply a sufficient array and quantity of nutrients to support the proliferation and persistence of its microbial community. In this investigation, we have examined such a nutritional environment by determining the symbiotic competence of auxotrophic mutants of the bioluminescent bacterium Vibrio fischeri, and have demonstrated that the host squid Euprymna scolopes provides at least 9 aa to the growing culture of symbiotic V. fischeri present in its light-emitting organ. We also collected and analyzed the extracellular fluid from this organ, in which the symbionts reside, and confirmed that it contained significant amounts of amino acids. The combined results suggested that host-derived free amino acids, as well as peptides or proteins, are a source of the amino acids that support the growth of the symbionts. This work describes a technique to sample the symbionts and their surrounding environment without contamination by host tissue components and, in combination with molecular genetic studies, allows the characterization of the nutritional conditions that support a cooperative animal-bacterial symbiosis.
动物通常会被多种细菌共生体定殖，其中许多是共生菌，在许多情况下，它们对宿主的正常发育和生长甚至是必不可少的。作为交换，宿主必须提供足够种类和数量的营养物质，以支持其微生物群落的增殖和持续存在。在本研究中，我们通过测定发光细菌费氏弧菌营养缺陷型突变体的共生能力来研究这样一种营养环境，并证明宿主鱿鱼短尾乌贼向其发光器官中生长的共生费氏弧菌培养物提供了至少9种氨基酸。我们还收集并分析了共生菌所在的该器官的细胞外液，并证实其中含有大量氨基酸。综合结果表明，宿主来源的游离氨基酸以及肽或蛋白质是支持共生菌生长的氨基酸来源。这项工作描述了一种在不被宿主组织成分污染的情况下对共生菌及其周围环境进行采样的技术，并且与分子遗传学研究相结合，能够对支持动物-细菌共生合作的营养条件进行表征。
