On October 19th, 2021, Marian Dominguez-Mirazo successfully defended her thesis proposal entitled “Cell fate modulation from infection to population dynamics’’ and was officially admitted for her Ph.D. candidacy.

To learn more about Marian’s thesis work, read the abstract below.

Viruses are obligate parasites that require their host’s synthesis machinery to replicate. Viruses are the most abundant biological entity on our planet yet account for less than 0.05% of the total biomass. Viruses of microbes can be found virtually everywhere, from the deep sea to the human gut. They can have impacts at the ecosystem level.

Yet viruses can do more than kill their microbial hosts. Some viruses, such as temperate bacteriophage, are capable of carrying out two types of infection: lytic or lysogenic. In a lysogenic pathway, there is viral integration into the host’s genome. Following viral integration, the virus is transmitted vertically until environmental stressors, or spontaneous induction, trigger lysis. In some cases, viral genetic material can be degraded producing a defective prophage incapable of lysing. As long as their genome remains integrated, viral survival and success depend directly on the host’s prosperity. The virus-host relationship is not limited to antagonism. Instead, the relationship is complicated and can range from antagonism to mutualism by means of superinfection exclusion or incorporation of beneficial genes by prophages.

The lytic pathway can beneficially or deleteriously shape host populations as we observe during viral invasion of biofilms. Biofilms are a complex form of bacterial organization where bacteria stick to each other and/or to a surface surrounded by an extracellular matrix of DNA, lipids, and proteins. The biofilm’s matrix and architecture can confer protection to bacteria from environmental hazards like antibiotics, microbial predators, or viruses. Viral invasion of biofilms can result in deleterious outcomes for the host like biofilm elimination, or beneficial ones like enhanced biofilm protection.

The microbial population dynamics resulting from viral invasion depend largely on viral traits. The latent period is the time from viral adsorption to viral progeny release. Latent period variability in a population can arise from cell-to-cell variability and have a profound impact on virus-microbe dynamics.

Using modeling and data analysis, we aim to study cell fate modulation through viral infection and its impact on microbial populations. We intend to explore the virus-microbe relationship at different stages of the infection cycle through 1) study of the presence and role of defective prophage in plant-associated bacteria, 2) reexamination of the viral latent period in virus-microbe systems focusing on the nature and impact of latent period variability in microbial populations, and 3) evaluation of the effect of phage invasion on biofilm-forming bacterial communities.