Marine Biotechnology Fellowship: Role of Chromosome- Associated DNA Binding Proteins in the Viable but Nonculturable State of Vibrio Vulnificus

麦戈文9321699在海水中可以计数的活性细菌中，大约有50%可以抵抗尝试培养。其中一个原因可能是，细菌在自然压力条件下，能够进入有生命但不生长的状态。可存活但不可培养(VBNC)状态涉及代谢程序，在该程序中，细胞保持活性并保持低水平的新陈代谢，但不能被培养。了解控制进入这种状态的因素可能会提供进入海洋不可聚集细菌生物学的窗口，研究进入和离开VBNC状态的最具特征性的系统是海洋细菌创伤弧菌。V.创伤菌进入VBNC状态是对温度下降的反应。进入VBNC状态会带来DNA水平的问题：与染色体相关的DNA结合蛋白(有时称为组蛋白样蛋白)可能在VBNC状态中发挥重要作用。其中一种蛋白质，HNS，已经被证明在体内可以沉默转录，在体外可以稳定和有序的DNA结构。它的多效性表明，这种蛋白质在让细胞感知各种类型的环境变化方面发挥了作用。HNS是一种丰富的、冷诱导的蛋白质，在细胞生长周期的整个过程中浓度变化，在静止期达到最大浓度，这是一个相对代谢停滞期。该项目将测试这一假设，即在温度下降期间，HNS的创伤弧菌同源物被诱导，使正常生长所需基因的表达沉默，并导致该细菌的VBNC状态。这样的系统可以解释海洋环境中存在的非可培养细菌的很大一部分。***

McGovern 9321699 Approximately 50% of the active bacteria that can be counted in seawater resist attempts to culture. One reason may be that bacteria are capable, under natural conditions of stress, of entering a viable but nongrowing state. The viable but nonculturable (VBNC) state involves a metabolic program in which the cell remains viable and maintains a low level of metabolism, but cannot be cultured. Understanding the factors that govern entry into this state may provide a window of entry into the biology of the uncluturable bacteria of the ocean, The best characterized system for studying entry into and exit form the VBNC state is the marine bacterium Vibrio vulnificus. V. vulnificus enters the VBNC state in response to temperature downshifts. Entry into the VBNC state poses problems at the DNA level: the chromosome-associated DNA binding proteins (sometimes called "histone-like" proteins) may play an important role in the VBNC state. One of the these proteins, HNS, has been shown to silence transcription in vivo and to stabilize and ordered DNA structure in vitro. Its pleiotropic effects indicate that this protein plays a role in allowing cells to sense various types of environmental change. HNS is an abundant, cold-inducible protein that varies in concentration over the course of a cell's growth cycle, reaching its maximal concentration during stationary phase, a period of relative metabolic quiescence. This project will test the hypothesis that during a temperature downshift, the V. vulnificus homolog of HNS is induced, silencing expression of genes needed for normal growth and leading to the VBNC state in that bacterium. Such a system could account for a significant portion of the nonculturable bacteria present in the ocean environment. ***