Regulation of Light Directed Movement in Cyanobacteria

蓝藻可以在广泛的环境中生存和繁衍，并经常在海洋栖息地以及微生物垫和生物膜中占据主导地位。它们无处不在的全球分布在一定程度上反映了它们应对温度、营养和光照水平广泛波动的能力。Bhaya博士特别感兴趣的是蓝藻感知光源并移动到光源或远离光源的能力，从而优化光合作用的条件。这个项目将帮助科学界了解这一至关重要的实验的分子基础。这种现象，称为趋光性，是众所周知的，但鲜为人知。最近，Bhaya博士和她的同事们证明了聚球藻的趋光性是一种表面依赖的现象，需要IV型菌毛，表面附属物与抽动和社会运动有关，以及细菌病原体与宿主的联系。这位研究人员利用聚球藻基因组已经完全测序的事实来生成一个标记的运动性突变体文库。她将把工作重点放在一类映射到趋化基因(CHE)的突变上。虽然趋化蛋白在肠道细菌中的作用已被很好地理解，但尚不清楚已建立的许多范例是否延伸到其他系统中的Che蛋白的操作。聚球藻至少有三个CHE基因座，其中两个与运动反应有关。此外，研究人员分离出的一个突变体在编码一种蛋白质的基因中存在损伤，该蛋白质的结构域使人想起维管植物中光敏色素的发色团结合域。为了阐明产生和控制运动的因素，Bhaya博士将使用延时视频显微镜实时记录野生型和突变株的运动。这将使她能够第一次观察单个细胞和细胞群体的运动，从而提出关于控制运动的参数的基本问题。这项工作的第二个方面是使用分子和生化工具来标记和/或突变特定的蛋白质，以便更好地了解调节趋光性的蛋白质之间的相互作用。

Cyanobacteria can survive and flourish in a broad range of environments, and often dominate in marine habitats as well as in microbial mats and biofilms. Their ubiquitous global distribution reflects, in part, their ability to cope with wide fluctuations in temperature, nutrient, and light levels. Dr. Bhaya is particularly interested in the ability of cyanobacteria to perceive and move towards or away from a light source and thereby optimize conditions for photosynthesis. This project will help the scientific community understand the molecular basis of this critically important trait.This phenomenon, termed phototaxis, is well-known but little understood. Recently Dr.Bhaya and her colleagues have demonstrated that phototaxis in Synechocystis is a surface-dependent phenomenon that requires type IV pili, surface appendages implicated in both twitching and social motility and the association of bacterial pathogens with their hosts. This investigator has taken advantage of the fact that the Synechocystis genome has been entirely sequenced to generate a library of tagged motility mutants. She will focus her work on a class of mutants that map to chemotaxis-like (che) genes. While the role of chemotaxis proteins is fairly well-understood in enteric bacteria, it is not clear whether many of the paradigms that have been established extend to the operation of Che proteins in other systems. Synechocystis has at least three che loci, two of which are involved in motility responses. Furthermore, one of the mutants that the investigator has isolated has a lesion in a gene encoding a protein with a domain reminiscent of the chromophore-binding domain of phytochrome in vascular plants. To elucidate the elements involved in generating and controlling motility, Dr.Bhaya will use time-lapse video microscopy to record movement in real time in both wild type and mutant strains. This will allow her to observe, for the first time, movement of single cells and cell populations, and thus to ask fundamental questions about the parameters that govern motility. The second aspect of the work is to use molecular and biochemical tools to tag and/or mutate specific proteins, such that the interactions among the proteins that regulate phototaxis can be better understood.