Amblyomma americanum (Lone star tick) is an important disease vector in the United States. It transmits several human pathogens, including the agents of human monocytic ehrlichiosis, tularemia, and southern tick-associated rash illness. Blood-feeding insects (Class Insecta) depend on bacterial endosymbionts to provide vitamins and cofactors that are scarce in blood. It is unclear how this deficiency is compensated in ticks (Class Arachnida) that feed exclusively on mammalian blood. A bacterium related to Coxiella burnetii, the agent of human Q fever, has been observed previously within cells of A. americanum. Eliminating this bacterium (CLEAA, Coxiella-like endosymbiont of A. americanum) with antibiotics reduced tick fecundity, indicating that it is an essential endosymbiont. In an effort to determine its role within this symbiosis, we sequenced the CLEAA genome. While highly reduced (656,901 bp) compared with C. burnetii (1,995,281 bp), the CLEAA genome encodes most major vitamin and cofactor biosynthesis pathways, implicating CLEAA as a vitamin provisioning endosymbiont. In contrast, CLEAA lacks any recognizable virulence genes, indicating that it is not a pathogen despite its presence in tick salivary glands. As both C. burnetii and numerous “Coxiella-like bacteria” have been reported from several species of ticks, we determined the evolutionary relationship between the two bacteria. Phylogeny estimation revealed that CLEAA is a close relative of C. burnetii, but was not derived from it. Our results are important for strategies geared toward controlling A. americanum and the pathogens it vectors, and also contribute novel information regarding the metabolic interdependencies of ticks and their nutrient-provisioning endosymbionts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.