Seminar Series in Quantitative Life Sciences and Medicine

How adaptive immunity constrains the composition and fate of large bacterial populations

Sidartha Goyal (University of Toronto)
Tuesday February 26, 12-1pm
deGrandpre Communication Centre, Montreal Neurological Institute

Abstract: Bacteria learn from past viral attacks by integrating small segments of viral genomes (spacers) into their DNA to neutralize future attacks. This memory of past attacks is then inherited along a bacterium’s lineage suggesting its effect on the fate and structure of the whole microbial population. Emphasizing the population-level impact of the adaptive immunity, recent experiments show that some bacteria regulate adaptive-immunity-associated genes via the quorum-sensing (QS) pathway. I will present a model that shows how from the highly stochastic dynamics of individual spacers emerges a rank-abundance distribution of spacers that is time invariant, a surprising prediction that is consistent with dynamic spacer-tracking data in experiments. This distribution depends on the state of the competing virus–bacteria population, which due to QS-based control exhibits multiple stable states with drastically different virus-bacterium composition.