Phages
Viruses are omnipresent in our world and occur almost everywhere where life can be found. Although viruses themselves are not regarded as living beings, they interact with them. Due to their non-independent replication or reproduction, they depend on the host's metabolism for their reproduction. Once a host is infected with a virus, the host metabolism is reprogrammed by the virus to produce a large number of identical virus copies and release them into the environment by lysis. Viruses, in general, are responsible for genetic diversity due to genetic exchange in horizontal gene transfer and are considered to be the driving force of the global marine geochemical cycles. There they also influence the availability of nutrients, the end of algal blooms and presumably control host population dynamics.
One of the most common and widespread organisms in the ocean, besides the genus Prochlorococcus, is Synechococcus. Both belong to the cyanobacteria and are globally the most important marine primary producers. Due to their small size, they are classified as picoplankton and are considered the smallest known photosynthetic organisms. Regarding the special light conditions in the ocean, they possess light-harvesting complexes (phycobilisomes) that harvest light energy and direct this into photosynthesis for energy production.
Viruses that infect cyanobacteria are called cyanophages. Interestingly, genes have been found in cyanophages that are not directly involved in virus replication and seem to originate from the host. During infection, these genes and the encoded proteins are actively involved in altering the host's metabolism to maintain the essential host metabolic pathway. Regarding this function, they are called AMGs (auxiliary metabolic genes). The function of these genes and their encoded proteins include for example the maintenance of protein biosynthesis, nucleotide synthesis, carbon metabolism and photosynthesis for energy production. It is generally believed that AMGs perform the same function as their cyanobacterial orthologues and are derived from their hosts or related bacteria. Cyanophages AMG encoded proteins resemble a variety of enzymes that are responsible for maintaining energy production in the host when expressed in cyanobacteria during phage infection. The regulation of these genes and their influence on the host are not sufficiently studied.
The study of phage enzymes is a current research topic of our group and provides an insight into the evolution of tetrapyrrole biosynthesis and its role in the ecosystem. In this project, we investigate the influence of selected AMGs on host metabolism and particularly photosynthesis.