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%抵抗培养的尝试。 一个原因可能是细菌在自然的压力条件下能够进入一个有活力但不生长的状态。 活的但不可培养（VBNC）状态涉及一种代谢程序，其中细胞保持活力并保持低水平的代谢，但不能培养。 了解控制进入这种状态的因素可能会提供一个进入海洋不可培养细菌生物学的窗口，研究进入和退出VBNC状态的最佳特征系统是海洋细菌创伤弧菌。创伤弧菌进入VBNC状态以响应温度的降低。 进入VBNC状态会在DNA水平上产生问题：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。 这些蛋白质之一，HNS，已被证明在体内沉默转录，并在体外稳定和有序的DNA结构。 它的多效性表明，这种蛋白质在允许细胞感知各种类型的环境变化方面发挥作用。HNS是一种丰富的冷诱导蛋白，其浓度在细胞生长周期的过程中变化，在稳定期（相对代谢静止期）达到其最大浓度。 该项目将测试以下假设：在温度下降期间，HNS的创伤弧菌同源物被诱导，使正常生长所需的基因表达沉默，并导致该细菌中的VBNC状态。 这样的系统可以解释海洋环境中存在的不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. ***