Insects that live exclusively on vertebrate blood utilize symbiotic bacteria as a source of essential compounds, e.g., B vitamins. In louse flies, the most frequent symbiont originated in genus Arsenophonus, known from a wide range of insects. Here, we analyze genomic traits, phylogenetic origins, and metabolic capacities of 11 Arsenophonus strains associated with louse flies. We show that in louse flies, Arsenophonus established symbiosis in at least four independent events, reaching different stages of symbiogenesis. This allowed for comparative genomic analysis, including convergence of metabolic capacities. The significance of the results is twofold. First, based on a comparison of independently originated Arsenophonus symbioses, it determines the importance of individual B vitamins for the insect host. This expands our theoretical insight into insect-bacteria symbiosis. The second outcome is of methodological significance. We show that the comparative approach reveals artifacts that would be difficult to identify based on a single-genome analysis.

• Klíčová slova
• bacterial symbiosis, coevolution, genome evolution, hematophagy,
• MeSH
• Anoplura * MeSH
• Bacteria MeSH
• Diptera * mikrobiologie   MeSH
• Enterobacteriaceae MeSH
• fylogeneze MeSH
• Gammaproteobacteria * genetika   MeSH
• hmyz MeSH
• symbióza MeSH
• vitamin B komplex * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• vitamin B komplex * MeSH

Insect microbiomes influence many fundamental host traits, including functions of practical significance such as their capacity as vectors to transmit parasites and pathogens. The knowledge on the diversity and development of the gut microbiomes in various blood feeding insects is thus crucial not only for theoretical purposes, but also for the development of better disease control strategies. In Triatominae (Heteroptera: Reduviidae), the blood feeding vectors of Chagas disease in South America and parts of North America, the investigation of the microbiomes is in its infancy. The few studies done on microbiomes of South American Triatominae species indicate a relatively low taxonomic diversity and a high host specificity. We designed a comparative survey to serve several purposes: (I) to obtain a better insight into the overall microbiome diversity in different species, (II) to check the long term stability of the interspecific differences, (III) to describe the ontogenetic changes of the microbiome, and (IV) to determine the potential correlation between microbiome composition and presence of Trypanosoma cruzi, the causative agent of Chagas disease. Using 16S amplicons of two abundant species from the southern US, and four laboratory reared colonies, we showed that the microbiome composition is determined by host species, rather than locality or environment. The OTUs (Operational Taxonomic Units) determination confirms a low microbiome diversity, with 12-17 main OTUs detected in wild populations of T. sanguisuga and T. protracta. Among the dominant bacterial taxa are Acinetobacter and Proteiniphilum but also the symbiotic bacterium Arsenophonus triatominarum, previously believed to only live intracellularly. The possibility of ontogenetic microbiome changes was evaluated in all six developmental stages and feces of the laboratory reared model Rhodnius prolixus. We detected considerable changes along the host's ontogeny, including clear trends in the abundance variation of the three dominant bacteria, namely Enterococcus, Acinetobacter, and Arsenophonus. Finally, we screened the samples for the presence of Trypanosoma cruzi. Comparing the parasite presence with the microbiome composition, we assessed the possible significance of the latter in the epidemiology of the disease. Particularly, we found a trend toward more diverse microbiomes in Trypanosoma cruzi positive T. protracta specimens.

• Klíčová slova
• Rhodnius prolixus, Triatominae, Trypanosoma cruzi, microbiome, ontogeny,
• Publikační typ
• časopisecké články MeSH

Symbiotic interactions between insects and bacteria are ubiquitous and form a continuum from loose facultative symbiosis to greatly intimate and stable obligate symbiosis. In blood-sucking insects living exclusively on vertebrate blood, obligate endosymbionts are essential for hosts and hypothesized to supplement B-vitamins and cofactors missing from their blood diet. The role and distribution of facultative endosymbionts and their evolutionary significance as seeds of obligate symbioses are much less understood. Here, using phylogenetic approaches, we focus on the Hippoboscidae phylogeny as well as the stability and dynamics of obligate symbioses within this bloodsucking group. In particular, we demonstrate a new potentially obligate lineage of Sodalis co-evolving with the Olfersini subclade of Hippoboscidae. We also show several likely facultative Sodalis lineages closely related to Sodalis praecaptivus (HS strain) and suggest repeated acquisition of novel symbionts from the environment. Similar to Sodalis, Arsenophonus endosymbionts also form both obligate endosymbiotic lineages co-evolving with their hosts (Ornithomyini and Ornithoica groups) as well as possibly facultative infections incongruent with the Hippoboscidae phylogeny. Finally, we reveal substantial diversity of Wolbachia strains detected in Hippoboscidae samples falling into three supergroups: A, B, and the most common F. Altogether, our results prove the associations between Hippoboscoidea and their symbiotic bacteria to undergo surprisingly dynamic, yet selective, evolutionary processes strongly shaped by repeated endosymbiont replacements. Interestingly, obligate symbionts only originate from two endosymbiont genera, Arsenophonus and Sodalis, suggesting that the host is either highly selective about its future obligate symbionts or that these two lineages are the most competitive when establishing symbioses in louse flies.

• Klíčová slova
• Arsenophonus, Louse flies, Phylogeny, Replacements, Sodalis, Wolbachia,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The genus Arsenophonus is a group of symbiotic, mainly insect-associated bacteria with rapidly increasing number of records. It is known from a broad spectrum of hosts and symbiotic relationships varying from parasitic son-killers to coevolving mutualists.The present study extends the currently known diversity with 34 samples retrieved mainly from hippoboscid (Diptera: Hippoboscidae) and nycteribiid (Diptera: Nycteribiidae) hosts, and investigates phylogenetic relationships within the genus. RESULTS: The analysis of 110 Arsenophonus sequences (incl. Riesia and Phlomobacter), provides a robust monophyletic clade, characterized by unique molecular synapomorphies. On the other hand, unstable inner topology indicates that complete understanding of Arsenophonus evolution cannot be achieved with 16S rDNA. Moreover, taxonomically restricted Sampling matrices prove sensitivity of the phylogenetic signal to sampling; in some cases, Arsenophonus monophyly is disrupted by other symbiotic bacteria. Two contrasting coevolutionary patterns occur throughout the tree: parallel host-symbiont evolution and the haphazard association of the symbionts with distant hosts. A further conspicuous feature of the topology is the occurrence of monophyletic symbiont lineages associated with monophyletic groups of hosts without a co-speciation pattern. We suggest that part of this incongruence could be caused by methodological artifacts, such as intragenomic variability. CONCLUSION: The sample of currently available molecular data presents the genus Arsenophonus as one of the richest and most widespread clusters of insect symbiotic bacteria. The analysis of its phylogenetic lineages indicates a complex evolution and apparent ecological versatility with switches between entirely different life styles. Due to these properties, the genus should play an important role in the studies of evolutionary trends in insect intracellular symbionts. However, under the current practice, relying exclusively on 16S rRNA sequences, the phylogenetic analyses are sensitive to various methodological artifacts that may even lead to description of new Arsenophonus lineages as independent genera (e.g. Riesia and Phlomobacter). The resolution of the evolutionary questions encountered within the Arsenophonus clade will thus require identification of new molecular markers suitable for the low-level phylogenetics.

• MeSH
• bakteriální geny MeSH
• Diptera mikrobiologie   MeSH
• DNA bakterií genetika   MeSH
• Enterobacteriaceae klasifikace   genetika   MeSH
• fylogeneze * MeSH
• molekulární evoluce * MeSH
• RNA ribozomální 16S genetika   MeSH
• sekvenční analýza DNA MeSH
• sekvenční seřazení MeSH
• symbióza MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• DNA bakterií MeSH
• RNA ribozomální 16S MeSH