Recently evolved Francisella-like endosymbiont outcompetes an ancient and evolutionarily associated Coxiella-like endosymbiont in the lone star tick (Amblyomma americanum) linked to the Alpha-gal syndrome

Authors: KUMAR, DEEPAK - University Of Southern Mississippi; SHARMA, SURENDRA - University Of Southern Mississippi; ADEGOKE, ABDULSALAM - University Of Southern Mississippi; KENNEDY, ASHLEY - State Of Delaware Division Of Fish & Wildlife; TUTEN, HOLLY - University Of Illinois; Li, Andrew; KARIM, SHAHID - University Of Southern Mississippi

Submitted to: Frontiers in Cellular and Infection Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2022
Publication Date: 4/12/2022
Citation: Kumar, D., Sharma, S.R., Adegoke, A., Kennedy, A., Tuten, H.C., Li, A.Y., Karim, S. 2022. Recently evolved Francisella-like endosymbiont outcompetes an ancient and evolutionarily associated Coxiella-like endosymbiont in the lone star tick (Amblyomma americanum) linked to the Alpha-gal syndrome. Frontiers in Cellular and Infection Microbiology. https://doi.org/10.3389/fcimb.2022.787209.
DOI: https://doi.org/10.3389/fcimb.2022.787209

Interpretive Summary: The lone star tick transmits viral and bacterial pathogens that cause various human diseases, such as ehrlichiosis, tularemia, and Southern Tick-Associated Rash Illness. In addition, mammalian meat allergy or Alpha-Gal Syndrome in humans is also found to be associated with bites of the lone star tick. The cases of Alpha-Gal Syndrome are increasing in recent years, but the underlying mechanisms that lead to the illness are poorly understood. ARS scientists joined force with university researchers to investigate microorganism composition in different developmental stages of the lone star tick using the 16S rRNA sequencing approach. Microbes co-existing with known pathogens within the ticks are known to influence pathogen infection and transmission. Results from this study indicate bacterial Coxiella-like endosymbionts traditionally associated with the lone star populations have been replaced by Francisella-like endosymbionts in all developmental stages of the lone star tick. The study raised the possibility that the newly acquired Francisella-like endosymbionts could be responsible for the enhanced capability of the lone star tick to cause Alpha-Gal Syndrome. The findings warrant further investigation into the molecular mechanisms of the Alpha-Gal Syndrome. Results obtained from this study will be of interest to tick biologists, tick-borne disease epidemiologists, and researchers who study Alpha-Gal Syndrome and other tick-borne diseases affecting humans.

Technical Abstract: The lone star tick (Amblyomma americanum) is a competent vector of various emerging viral, bacterial, and protozoan pathogens and its bite is suspected to elicit Alpha-Gal syndrome. The composition of its bacterial communities residing within different developmental stages remains understudied. In this study, we assessed the microbiome of Am. americanum in all developmental stages, including eggs, unfed and blood-fed larvae, nymphs, adult males and females, and tissue types (salivary glands, midgut, and ovaries) by utilizing 16S rRNA sequencing. Taxonomic analysis suggested that more than 85% of the reads for each life stage or tick tissue (salivary gland, midgut, and ovary) are represented by Francisellaceae, Midichloriaceae, Rickettsiaceae, and Spirochaetaceae. These results showed stable bacterial composition in immature and mature developmental stages. The Coxiella-like endosymbionts (CLE), an endosymbiont traditionally associated with Am. americanum populations was replaced with a Francisella-like endosymbiont (FLE) in all developmental stages and dissected tissues except unfed ovary. The precise mechanisms providing the advantage to FLE are yet to be determined, including if this change is involved in Am. americanum’s enhanced capability to cause Alpha-Gal Syndrome.