Maintain socially distancing: Do viruses control the origins of multicellularity?

Multicellularity has evolved numerous times, not only in Eukaryotes, but also within the Eubacteria. There is therefore near universal selection driving social cooperation between individual cells in the tree of life.
Cyanobacteria arose ~2.5 billion years ago, producing all free oxygen on Earth, and seeding the formation of plants through endosymbiosis. It is thought that the last common ancestor of all Cyanobacteria was multicellular1. Today, within Cyanobacteria, diverse forms of multicellularity exist (Fig. 1). These include filaments, and colonies composed of sheets and spheres. Higher order cooperation also exists, in the form of photogranules, which in some cases, can propel a cm sized colony toward light. Moreover, individual cells can specialise, forming nitrogen-fixing heterocysts, or stress resistant sprores called akinetes, which sacrifice themselves for the good of the colony. Many of these social behaviours are facultative, meaning the colony can switch-on or off in response to stimuli.
Whilst the function of these forms of multicellularity are thought to be well understood, the genetic underpinnings and how these early interactions began to evolve remains completely unknown. A popular hypothesis states that simple single-celled organisms began to form colonies to protect themselves from grazing, whereby the cells in the interior of the colony are offered protection. Indeed, in simple laboratory experiments, usually unicellular algae, arrange themselves in multicellular structures in the presence of a ciliate grazer2.
Conversely, bacteria are also susceptible to viruses. These viral epidemics are normally thwarted by spatial isolation between bacterial cells. When bacteria are isolated, diffusion constants of the virus limit transmission, protecting the population. Thus, like in humans, social distancing prevents viral transmission.
Therefore, early initial interactions between cells forming a colony are at risk from being wiped-out by a virus. How multicellular bacteria avoid the viral trap is completely unknown.
During this project, you will seek to understand whether multicellular Cyanobacteria can resist viral infection. You will use model strains of multicellular Cyanobacteria to isolate and characterise viruses against different host morphotypes. You will combine this with time-lapse microscopy to visualise how progression develops, and whether infection causes large scale behaviour change in the colony.