REQUIREMENTS FOR BACTERIAL COLONIZATION OF ANIMAL TISSUE

共生(互惠)和致病之间有一条细微的界线。大多数动物(如果不是全部的话)都被细菌侵占，其中许多细菌--生物体的“正常菌群”--是被容忍的，甚至是被鼓励的。为了与动物建立共生关系，原核生物必须能够识别和响应特定的环境，与宿主建立沟通，在宿主组织中定居，逃避防御机制，持续和繁殖。这些步骤中的每一个都反映在病原相互作用中，无论是初级的还是机会性的--即使是正常的菌群，在过度繁殖或引入它们通常不居住的地区时，也有致病的潜力。尽管细菌-动物共生现象无处不在，但人们对这些相互作用的遗传和分子细节知之甚少。除了增加对这些重要的原核生物-真核生物联盟的基本了解外，共生相互作用的研究有望提高对病原体如何采用、颠覆或绕过导致共生的机制以及为什么它们引起真核细胞不同反应的理解。生物发光海洋细菌费氏弧菌与其宿主乌贼Euprymna scolope之间的共生为研究细菌的生物学提供了一个极好的机会，这种细菌可以与动物宿主形成长期的互惠关系。这种共生关系在生物层面上已经得到了很好的描述。我们现在建议开始对这些生物之间的相互作用进行详细的分子表征，包括共生状态的建立，两个生物之间的信号传递，以及随着共生的进展在双方中发生的发育变化。这项拟议的研究将通过对在最初共生事件中有缺陷的转座子插入突变体的直接筛选，来调查寄主组织对费斯切里病毒定植的要求。关键定植基因的鉴定和鉴定将为理解原核生物和真核生物在建立长期联合过程中的信号交换奠定基础。

There is a fine line between symbiosis (mutualism) and pathogenesis. Most, if not all, animals are colonized by bacteria, many of which-the organism's "normal flora"-are tolerated or even encouraged. To establish a symbiotic relationship with an animal, a prokaryotic organism must be able to recognize and respond to a specific environment, establish communication with the host, colonize the host tissue, evade defense mechanisms, persist and multiply. Each of these steps is mirrored in pathogenic interactions, whether primary or opportunistic-and even normal flora have pathogenic potential in the event of excessive multiplication or introduction into areas they do not ordinarily inhabit. Despite the ubiquity of bacterium-animal symbioses, little is known about the genetic and molecular details of these interactions. In addition to increasing basic understanding of these important prokaryote-eukaryote alliances, the study of symbiotic interactions is expected to improve understanding of how pathogenic organisms adopt, subvert, or bypass the mechanisms leading to symbiosis and why they provoke dissimilar responses from the eukaryotic cell. The symbiosis between the bioluminescent marine bacterium Vibrio fischeri and its host, the squid Euprymna scolopes, provides an excellent opportunity to study the biology of a bacterium which can form a long- term, mutualistic association with an animal host. The symbiosis has been well-characterized at the organismal level. We now propose to begin the detailed molecular characterization of the interactions between these organisms, including establishment of the symbiotic state, signalling between the two organisms and developmental changes occurring in both partners as the symbiosis progresses. The proposed research will investigate the requirements for V fischeri colonization of host tissue, using a straightforward screen for transposon-insertion mutants defective in the initial symbiotic events. Identification and characterization of the critical colonization genes will lay the foundation for understanding signal exchange between a prokaryote and a eukaryote during the establishment of a long-term association.