Hard ticks of the order Ixodidae serve as vectors for numerous human pathogens, including the causative agent of Lyme Disease Borrelia burgdorferi. Tick-associated microbes can influence pathogen colonization, offering the potential to inhibit disease transmission through engineering of the tick microbiota. Here, we investigate whether B. burgdorferi encounters abundant bacteria within the midgut of wild adult Ixodes scapularis, its primary vector. Through the use of controlled sequencing methods and confocal microscopy, we find that the majority of field-collected adult I. scapularis harbor limited internal microbial communities that are dominated by endosymbionts. A minority of I. scapularis ticks harbor abundant midgut bacteria and lack B. burgdorferi. We find that the lack of a stable resident midgut microbiota is not restricted to I. scapularis since extension of our studies to I. pacificus, Amblyomma maculatum, and Dermacentor spp showed similar patterns. Finally, bioinformatic examination of the B. burgdorferi genome revealed the absence of genes encoding known interbacterial interaction pathways, a feature unique to the Borrelia genus within the phylum Spirochaetes. Our results suggest that reduced selective pressure from limited microbial populations within ticks may have facilitated the evolutionary loss of genes encoding interbacterial competition pathways from Borrelia.
This essay highlights recommendations to make academic biology more inclusive of LGBTQ+ individuals. These recommendations are drawn from the literature and the collective experience of the 26-member author team.
1Hard ticks of the order Ixodidae serve as vectors for numerous human pathogens, including the 2 causative agent of Lyme Disease Borrelia burgdorferi. Tick-associated microbes can influence 3 pathogen colonization, offering the potential to inhibit disease transmission through engineering 4 of the tick microbiota. Here, we investigate whether B. burgdorferi encounters abundant bacteria 5 within the midgut of wild adult Ixodes scapularis, its primary vector. Through the use of 6 controlled sequencing methods and confocal microscopy, we find that the majority of field-7 collected adult I. scapularis harbor limited internal microbial communities that are dominated by 8 endosymbionts. A minority of I. scapularis ticks harbor abundant midgut bacteria and lack B. 9 burgdorferi. We find that the lack of a stable resident midgut microbiota is not restricted to I. 10 scapularis since extension of our studies to I. pacificus, Amblyomma maculatum, and 11Dermacentor spp showed similar patterns. Finally, bioinformatic examination of the B. 12 burgdorferi genome revealed the absence of genes encoding known interbacterial interaction 13 pathways, a feature unique to the Borrelia genus within the phylum Spirochaetes. Our results 14 suggest that reduced selective pressure from limited microbial populations within ticks may have 15 facilitated the evolutionary loss of genes encoding interbacterial competition pathways from 16Borrelia.
The Haller's organ plays a crucial role in a tick's ability to detect hosts. Even though this sensory organ is vital to tick survival, the morphology of this organ is not well understood. The objective of this study was to characterize variation in the morphological components of the Haller's organ of three medically important tick species using quantitative methods. The Haller's organs of Ixodes scapularis Say (Ixodida: Ixodidae) (black-legged tick), Amblyomma americanum (L.) (Ixodida: Ixodidae) (lone star tick), and Dermacentor variabilis (Say) (Ixodida: Ixodidae) (American dog tick) were morphologically analyzed using environmental scanning electron microscopy and geometric morphometrics, and the results were statistically interpreted using canonical variate analysis. Our data reveal significant, quantitative differences in the morphology of the Haller's organ among all three tick species and that in D. variabilis the sensory structure is sexually dimorphic. Studies like this can serve as a quantitative basis for further studies on sensor physiology, behavior, and tick species life history, potentially leading to novel methods for the prevention of tick-borne disease.
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