The sequencing and annotation of two bacteriophages isolated from the cyanobacterium Acaryochloris

海洋蓝藻(蓝藻)约占全球碳固定总量的四分之一，从而减轻了人类二氧化碳排放的影响。噬藻体是控制蓝藻进化和种群遗传学的主要因素之一。这五个完全测序的噬藻体基因组表明，这两种生物的生物学是紧密相连的。令人惊讶的是，噬菌体获得了蓝藻基因组的一部分，它们在感染期间利用这些基因组，改变了宿主的生理。只有两个属的蓝藻的噬菌体被完全测序(聚球藻和原氯球菌属)。我们目前几乎不知道是否所有的噬藻体都获得了宿主基因，如果是的话，这些事件发生的时间是什么时候。为了理解这一点，有必要查看其他噬藻体基因组，看看它们是否表现出相同的特征。氰噬菌体很难分离和处理，但我已经从这两个属中已知的最接近的亲缘关系中分离出了两个噬菌体：无枝线虫。我提出了一项研究计划，对这两个噬菌体的基因组进行排序和注释。这一研究计划在许多方面都令人兴奋。蓝藻的宿主Acaryoloris很有趣，因为它是唯一利用叶绿素d而不是叶绿素a进行光合作用的生物。它还有一种独特的辅助色素排列。拥有叶绿素d意味着它可以在光谱的远红端吸收光线，这似乎允许生物能够在更暗的环境中生活，因此它被发现与海鞘(海鞘)有关，并生长在红藻的底部。我们将比较噬菌体与其蓝藻宿主的基因组含量(这是测序的最后阶段，将在噬菌体测序项目启动之前完成)。这将使我们能够看到这个系统中的噬菌体是否对非线虫的光合作用的进化和潜在的功能做出了贡献。我计划测序的噬菌体是从外面的海鞘中刮下来的。因此，它们是第一个从共生蓝藻中分离出来的噬藻体，也是第一个从无脊椎动物中分离出来的噬藻体。对这些噬菌体基因组的分析可能会揭示有利于蓝藻共生的基因。由于蓝藻也被认为生长在海鞘内，它们甚至可能含有无脊椎动物的基因。这些Acaryoloris噬菌体基因组的测序可能是理解噬藻体进化和一般进化的几个基本方面的关键。

Marine cyanobacteria (blue green algae) are responsible for approximately one-quarter of global carbon fixation, thereby mitigating the effects of human carbon dioxide emissions. One of the main factors that controls the evolution and population genetics of cyanobacteria is cyanophages. The five completely sequenced cyanophage genomes have shown that the biology of the two organisms is tightly interlinked. Amazingly phages have picked up parts of the cyanobacterial genome, which they use to their advantage during infection, altering the host physiology. Only phages from two genera of cyanobacteria have been fully sequenced (Synechococcus and Prochlorococcus). We currently have little idea if all cyanophages have picked up host genes and if so when these events occurred. In order to understand this it is necessary to look at other cyanophage genomes to see if they show the same traits. Cyanophage are difficult to isolate and to work with but I have isolated two bacteriophages from the closest known relative of these two genera; Acaryochloris. I propose a programme of research to sequence and annotate the genome these two phages. This research programme is exciting in a number of ways. The cyanobacterial host Acaryochloris is intriguing in that it is the only organism to photosynthesise using chlorophyll d rather than chlorophyll a. It also has a unique arrangement of accessory pigments. The possession of chlorophyll d means that it can absorb light in the far red end of the spectrum which appears to allow the organism to be able to live in much darker environments, hence it has been found associated with sea squirts (Ascidia) and growing on the underside of red algae. We will compare the genome content of the phages with its cyanobacterial host (this is in the final stages of being sequenced and will be finished before the phage sequencing project is initiated). This will allow us to see if phages in this system have contributed to the evolution and potentially to the functioning of photosynthesis in Acaryochloris. The bacteriophages I am proposing to sequence were scraped from the outside sea squirts. Thus they are the first cyanophages to be isolated from a symbiotic cyanobacterium and the first to have been isolated from an invertebrate. An analysis of the genomes of these phages may reveal genes which benefit the symbiotic nature of the cyanobacteria. As the cyanobacterium is also thought to grow inside the sea squirts, they may even contain genes from the invertebrate. The sequencing of these Acaryochloris phage genomes may hold the key to understanding several fundamental aspects of cyanophage evolution and evolution in general.