Resistance of Mice of the 129 Background to Yersinia pestis Maps to Multiple Loci on Chromosome 1

Polygenic plague resistance in the great gerbil uncovered by population sequencing

Pathogens can elicit high selective pressure on hosts, potentially altering genetic diversity over short evolutionary timescales. Intraspecific variation in immune response is observable as variable survivability from specific infections. The great gerbil (Rhombomys opimus) is a rodent plague host with a heterogenic but highly resistant phenotype. Here, we investigate the genomic basis for plague-resistant phenotypes by exposing wild-caught great gerbils to plague (Yersinia pestis). Whole genome sequencing of 10 survivors and 10 moribund individuals revealed a subset of genomic regions showing elevated differentiation. Gene ontology analysis of candidate genes in these regions demonstrated enrichment of genes directly involved in immune functions, cellular metabolism and the regulation of apoptosis as well as pathways involved in transcription, translation, and gene regulation. Transcriptomic analysis revealed that the early activated great gerbil immune response to plague consisted of classical components of the innate immune system. Our approach combining challenge experiments with transcriptomics and population level sequencing, provides new insight into the genetic background of plague-resistance and confirms its complex nature, most likely involving multiple genes and pathways of both the immune system and regulation of basic cellular functions.

Host adaptation to novel pathogen introduction: Predicting conditions that promote evolutionary rescue

Novel pathogen introduction can have drastic consequences for naive host populations, and outcomes can be difficult to predict. Evolutionary rescue (ER) provides a foundation for understanding whether hosts are driven to extinction or survive via adaptation. Currently, patterns of host population dynamics alongside evidence of adaptation are used to infer ER. However, the gap between established ER theory and complexity inherent in natural systems makes interpreting empirical patterns difficult because they can be confounded with ecological drivers of survival under current theory. To bridge this gap, we expand ER theory to include biological selective agents, such as pathogens. We find birth processes to be more important than previously theorised in determining ER potential. We employ a novel framework evaluating ER potential within natural systems and gain ability to identify system characteristics that make ER possible. Identifying these characteristics allows a shift from retrospective observation to a predictive mindset, and our findings suggest that ER occurrence may be more limited than previously thought. We use the plague system of Yersinia pestis infecting Cynomys ludovicianus (black-tailed prairie dogs) and Spermophilus beecheyi (California ground squirrels) as a case study.

Enterobacteria and host resistance to infection

Enterobacteriaceae are a large family of Gram-negative, non-spore-forming bacteria. Although many species exist as part of the natural flora of animals including humans, some members are associated with both intestinal and extraintestinal diseases. In this review, we focus on members of this family that have important roles in human disease: Salmonella, Escherichia, Shigella, and Yersinia, providing a brief overview of the disease caused by these bacteria, highlighting the contribution of animal models to our understanding of their pathogenesis and of host genetic determinants involved in susceptibility or resistance to infection.