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      Sharing the Ride: Ixodes scapularis Symbionts and Their Interactions

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          The deer tick Ixodes scapularis transmits a variety of disease agents in the United States, spreading the bacteria that causes Lyme borreliosis, the protozoan agent of babesiosis, and viruses such as Powassan. However, a variety of other organisms have also evolved symbiotic relationships with this tick species, and it seems likely that some of these microbes have simultaneously coevolved mechanisms to impact each other and their tick host. The number of organisms identified as I. scapularis symbionts has increased seemingly exponentially with the advent of PCR and next generation sequencing technologies, but convincing arguments have proposed that some of these are of environmental origin, unadapted to surviving the physiological conditions of the tick or that they are artifacts of ultrasensitive detection methods. In this review, we examine the diversity of the known microbes occurring within the I. scapularis microbiome, the evidence for interactions between microbes, and discuss whether some organisms reported to be symbionts of I. scapularis are experimental artifacts.

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          Most cited references 105

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          Reagent and laboratory contamination can critically impact sequence-based microbiome analyses

          Background The study of microbial communities has been revolutionised in recent years by the widespread adoption of culture independent analytical techniques such as 16S rRNA gene sequencing and metagenomics. One potential confounder of these sequence-based approaches is the presence of contamination in DNA extraction kits and other laboratory reagents. Results In this study we demonstrate that contaminating DNA is ubiquitous in commonly used DNA extraction kits and other laboratory reagents, varies greatly in composition between different kits and kit batches, and that this contamination critically impacts results obtained from samples containing a low microbial biomass. Contamination impacts both PCR-based 16S rRNA gene surveys and shotgun metagenomics. We provide an extensive list of potential contaminating genera, and guidelines on how to mitigate the effects of contamination. Conclusions These results suggest that caution should be advised when applying sequence-based techniques to the study of microbiota present in low biomass environments. Concurrent sequencing of negative control samples is strongly advised. Electronic supplementary material The online version of this article (doi:10.1186/s12915-014-0087-z) contains supplementary material, which is available to authorized users.
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            Genomic sequence of a Lyme disease spirochaete, Borrelia burgdorferi.

            The genome of the bacterium Borrelia burgdorferi B31, the aetiologic agent of Lyme disease, contains a linear chromosome of 910,725 base pairs and at least 17 linear and circular plasmids with a combined size of more than 533,000 base pairs. The chromosome contains 853 genes encoding a basic set of proteins for DNA replication, transcription, translation, solute transport and energy metabolism, but, like Mycoplasma genitalium, it contains no genes for cellular biosynthetic reactions. Because B. burgdorferi and M. genitalium are distantly related eubacteria, we suggest that their limited metabolic capacities reflect convergent evolution by gene loss from more metabolically competent progenitors. Of 430 genes on 11 plasmids, most have no known biological function; 39% of plasmid genes are paralogues that form 47 gene families. The biological significance of the multiple plasmid-encoded genes is not clear, although they may be involved in antigenic variation or immune evasion.
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              Natural microbe-mediated refractoriness to Plasmodium infection in Anopheles gambiae.

              Malaria parasite transmission depends on the successful transition of Plasmodium through discrete developmental stages in the lumen of the mosquito midgut. Like the human intestinal tract, the mosquito midgut contains a diverse microbial flora, which may compromise the ability of Plasmodium to establish infection. We have identified an Enterobacter bacterium isolated from wild mosquito populations in Zambia that renders the mosquito resistant to infection with the human malaria parasite Plasmodium falciparum by interfering with parasite development before invasion of the midgut epithelium. Phenotypic analyses showed that the anti-Plasmodium mechanism requires small populations of replicating bacteria and is mediated through a mosquito-independent interaction with the malaria parasite. We show that this anti-Plasmodium effect is largely caused by bacterial generation of reactive oxygen species.

                Author and article information

                Front Cell Infect Microbiol
                Front Cell Infect Microbiol
                Front. Cell. Infect. Microbiol.
                Frontiers in Cellular and Infection Microbiology
                Frontiers Media S.A.
                08 April 2020
                : 10
                Biology of Vector-Borne Viruses Section, Laboratory of Virology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Hamilton, MT, United States
                Author notes

                Edited by: Alejandro Cabezas-Cruz, Institut National de la Recherche Agronomique, France

                Reviewed by: Sukanya Narasimhan, Yale University, United States; Jianmin Zhong, Humboldt State University, United States; Aleksandra Krawczyk, National Institute for Public Health and the Environment, Netherlands

                *Correspondence: Philip E. Stewart pestewart@

                This article was submitted to Virus and Host, a section of the journal Frontiers in Cellular and Infection Microbiology

                Copyright © 2020 Stewart and Bloom.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Figures: 1, Tables: 2, Equations: 0, References: 106, Pages: 12, Words: 11215
                Funded by: Division of Intramural Research, National Institute of Allergy and Infectious Diseases 10.13039/100006492
                Cellular and Infection Microbiology


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