Bacterial viruses, phages, are ubiquitous and most numerous entities in the biosphere. Development of sequencing techniques has increased our understanding on the diversity of phages that have not been isolated due to lack of cultivable hosts and/or suitable isolation methods. While sequence data enables a better view to the viral diversity, at the same time lack of functional data and biological connection increases. Recently, different studies have found megaphages (mainly phages with a genome over 600 kbp) by assembling metagenomes from various environmental samples. However, no such isolates have been obtained thus far meaning that their characteristics and host interactions are completely unknown. This ERC project will enlighten the life of giant phages, the term coined for both jumbo and megaphages. This will be achieved by using the first megaphage isolates. During the project, evidence on the megaphage structure and host interactions with host will be provided. Using a unique set of different phage sizes infecting the same host the size correlation to different life history traits will be determined. Project will provide insight to the mutualistic relationship between bacteria and their viruses and reveal new mechanisms behind phage competition. The environmental preferences for the megaphage emergence and abundance in boreal freshwaters will be determined. Consequently, results will aid in understanding the role of megaphages in other environments such as gut microbiome and potentially provide avenues for developing new genetic tools. This project will open new understanding for microbial ecology and especially phage ecology.
