Mortality of marine picoplankton: viral infection, protistan grazing, bacterial cell defence interactions

海洋在决定世界气候方面起着重要作用。在某种程度上，这是由于被称为浮游植物的小型光合植物产生氧气和消耗二氧化碳。在远离海岸的大片海洋中心区域，非常小的单细胞蓝藻是浮游植物中数量最多的部分。这些蓝藻不断地生长和分裂，但它们也不断地被消耗。有两个主要的过程有助于消耗这些细胞。首先，它们可以被病毒感染和杀死，其次，它们可以被称为原生生物的小型单细胞食草动物用作食物。这是这两种死亡过程之间的相互作用，以及蓝藻已经形成的防御机制，这是本研究项目的重点。我们想知道这些蓝藻表面是否有特定的结构，使它们对食草动物没有吸引力。还有一种可能是，病毒改变了被感染的细胞，使它们不适合作为食物，否则病毒也会被吃掉。在海洋的大部分地区，蓝藻没有足够的营养，因此找出饥饿如何影响它们对放牧和病毒感染的易感性是很重要的。

The oceans play a major role in determining the world's climate. In part this is due to the production of oxygen and the consumption of carbon dioxide by small photosynthetic plants called phytoplankton. In the large central regions of the oceans, away from the coasts, very small unicellular cyanobacteria are the most numerous part of the phytoplankton. These cyanobacteria are continually growing and dividing, but they are also continuously being consumed. There are two major processes that contribute to the consumption of these cells. Firstly, they can be infected and killed by viruses and secondly they can be used as food by small single celled grazing animals called protists. It is the interaction between these two processes of mortality, together with the defence mechanisms that the cyanobacteria have developed, which are the focus of this research project. We would like to find out whether these cyanobacteria have specific structures on their surfaces that make them unattractive as food for the grazers. It is also possible that viruses alter the cells that they have infected to make them unattractive as food otherwise the virus would also get eaten. In most parts of the oceans there aren't enough nutrients for the cyanobacteria and it is important to find out how starvation affects their susceptibility to being grazed and infected by viruses.