University of Massachusetts Medical School Faculty Publications

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Department of Medicine, Division of Infectious Diseases and Immunology

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Article Preprint


Bacteria | Bacterial Infections and Mycoses | Ecology and Evolutionary Biology | Immunology and Infectious Disease | Microbiology | Parasitic Diseases | Parasitology


Microparasites selectively adapt in some hosts, known as host tropism. Transmitted through ticks and carried mainly by mammals and birds, the Lyme disease (LD) bacterium is a well-suited model to study such tropism. LD bacteria species vary in host ranges through mechanisms eluding characterization. By feeding ticks infected with different LD bacteria species, utilizing feeding chambers and live mice and quail, we found species-level differences of bacterial transmission. These differences localize on the tick blood meal, and complement, a defense in vertebrate blood, and a bacterial polymorphic protein, CspA, which inactivates complement by binding to a host complement inhibitor, FH. CspA selectively confers bacterial transmission to vertebrates that produce FH capable of allele-specific recognition. Phylogenetic analyses revealed convergent evolution as the driver of such findings, which likely emerged during the last glacial maximum. Our results identify LD bacterial determinants of host tropism, defining an evolutionary mechanism that shapes host-microparasite associations.


Microbiology, Microparasites, Lyme disease, host tropism

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bioRxiv 2021.02.09.430532; doi: Link to preprint on bioRxiv.


This article is a preprint. Preprints are preliminary reports of work that have not been certified by peer review.

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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.