[Seminar] Population structure of the pneumococcus is driven by selection on the groEL heat-sock protein: a whole-genome machine learning perspective

Seminar

Title: Population structure of the pneumococcus is driven by selection on the groEL heat-sock protein: a whole-genome machine learning perspective

Speaker: José Lourenço

Affiliation: Research departmental lecturer in infectious disease at the Department of Zoology, University of Oxford

Host: Raquel Sa-Leão Lab - Molecular Microbiology of Human Pathogens

Abstract:

Populations of Streptococcus pneumoniae (SP) are typically structured into groups of closely related lineages, but it is not clear whether they are maintained by selection or neutral processes. Here, we attempt to address this question by applying a machine learning technique to SP whole genomes. Our results indicate that lineages evolved through selection on the groEL protein. groEL is part of the essential groESL operon that enables a large range of proteins to fold correctly, thereby explaining why lineage structure is so stable within SP despite high levels of genetic transfer. SP is also antigenically diverse, exhibiting a variety of distinct capsular serotypes. Associations exist between lineage and capsular serotype but these can be easily perturbed, such as by vaccination. Overall, our analyses indicate that the evolution of SP can be conceptualized by selection acting on different timescales under different pressures: some patterns have locked in early (such as the epistatic interactions between groESL and a constellation of other genes) and preserve the differentiation of lineages, while others (such as the associations between capsular serotype and lineage) remain in continuous flux.