The parvorder Rhynchophthirina with a single genus Haematomyzus is a small group of ectoparasites of unclear phylogenetic position, related to sucking and chewing lice. Previous screening based on the 16S rRNA gene indicated that Haematomyzus harbors a symbiotic bacterium whose DNA exhibits a strong shift in nucleotide composition typical of obligate mutualistic symbionts in insects. Within Phthiraptera, the smallest known genomes are found in the symbionts associated with sucking lice, which feed exclusively on mammal blood, compared to the generally larger genomes of the symbionts inhabiting chewing lice, which feed on skin derivatives. In this study, we investigate the genome characteristics of the symbiont associated with Haematomyzus elephantis. We sequenced and assembled the H. elephantis metagenome, extracted a genome draft of its symbiotic bacterium, and showed that the symbiont has a significantly reduced genome, which is with 0.39 Mbp the smallest genome among the symbionts known from Phthiraptera. Multigenic phylogenetic analysis places the symbiont into one of three clusters composed of long-branched symbionts from other insects. More specifically, it clusters together with symbionts from several other sucking lice and also with Wigglesworthia glossinidia, an obligate symbiont of tsetse flies. Consistent with the dramatic reduction of its genome, the H. elephantis symbiont lost many metabolic capacities. However, it retained functional pathways for four B vitamins, a trait typical for symbionts in blood-feeding insects. Considering genomic, metabolic, and phylogenetic characteristics, the new symbiont closely resembles those known from several sucking lice rather than chewing lice.IMPORTANCERhynchophthirina is a unique small group of permanent ectoparasites that is closely related to both sucking and chewing lice. These two groups of lice differ in their morphology, ecology, and feeding strategies. As a consequence of their different dietary sources, i.e., mammals' blood vs vertebrate skin derivatives, they also exhibit distinct patterns of symbiosis with obligate bacterial symbionts. While Rhynchophthirina shares certain traits with sucking and chewing lice, the nature of its obligate symbiotic bacterium and its metabolic role is not known. In this study, we assemble the genome of symbiotic bacterium from Haematomyzus elephantis (Rhynchophthirina), demonstrating its close similarity and phylogenetic proximity to several symbionts of sucking lice. The genome is highly reduced (representing the smallest genome among louse-associated symbionts) and exhibits a significant loss of metabolic pathways. However, similar to other sucking louse symbionts, it retains essential pathways for the synthesis of several B vitamins.

• Keywords
• endosymbionts, genomics, lice,
• MeSH
• Bacteria * genetics   classification   isolation & purification   MeSH
• Phylogeny MeSH
• Genome, Bacterial * MeSH
• Phthiraptera * microbiology   MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Symbiosis * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• RNA, Ribosomal, 16S MeSH

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.

• Keywords
• bacterial symbiosis, coevolution, genome evolution, hematophagy,
• MeSH
• Anoplura * MeSH
• Bacteria MeSH
• Diptera * microbiology   MeSH
• Enterobacteriaceae MeSH
• Phylogeny MeSH
• Gammaproteobacteria * genetics   MeSH
• Insecta MeSH
• Symbiosis MeSH
• Vitamin B Complex * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Vitamin B Complex * MeSH

Psyllids are phloem-feeding insects that can transmit plant pathogens such as phytoplasmas, intracellular bacteria causing numerous plant diseases worldwide. Their microbiomes are essential for insect physiology and may also influence the capacity of vectors to transmit pathogens. Using 16S rRNA gene metabarcoding, we compared the microbiomes of three sympatric psyllid species associated with pear trees in Central Europe. All three species are able to transmit 'Candidatus Phytoplasma pyri', albeit with different efficiencies. Our results revealed potential relationships between insect biology and microbiome composition that varied during psyllid ontogeny and between generations in Cacopsylla pyri and C. pyricola, as well as between localities in C. pyri. In contrast, no variations related to psyllid life cycle and geography were detected in C. pyrisuga. In addition to the primary endosymbiont Carsonella ruddii, we detected another highly abundant endosymbiont (unclassified Enterobacteriaceae). C. pyri and C. pyricola shared the same taxon of Enterobacteriaceae which is related to endosymbionts harboured by other psyllid species from various families. In contrast, C. pyrisuga carried a different Enterobacteriaceae taxon related to the genus Sodalis. Our study provides new insights into host-symbiont interactions in psyllids and highlights the importance of host biology and geography in shaping microbiome structure.

• MeSH
• Enterobacteriaceae genetics   MeSH
• Hemiptera * microbiology   MeSH
• Insecta MeSH
• Humans MeSH
• Microbiota * genetics   MeSH
• Pyrus * MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Symbiosis MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• RNA, Ribosomal, 16S MeSH

Louse flies (Hippoboscidae) are permanent ectoparasites of birds and mammals. They have a cosmopolitan distribution with more than 200 described species. The aim of this study was to reveal host-vector-parasite associations between louse flies, birds, and trypanosomes. A total of 567 louse fly specimens belonging to 7 species were collected from birds at several localities in Czechia, including the rare species Ornithophila metallica and Ornithoica turdi. There was a significant difference in the occurrence of Ornithomya avicularia and Ornithomya fringillina on bird hosts according to their migratory status, O. fringillina being found more frequently on long-distance migrants. Trypanosomes were found in four species, namely, Ornithomya avicularia, O. fringillina, O. biloba, and Ornithoica turdi; the later three species are identified in this paper as natural trypanosome vectors for the first time. The prevalence of trypanosomes ranged between 5 and 19%, the highest being in O. biloba and the lowest being in O. fringillina. Phylogenetic analysis of the SSU rRNA gene revealed that a vast majority of trypanosomes from hippoboscids belong to the avian T. corvi/culicavium group B. Four new lineages were revealed in group B, with louse flies being probable vectors for some of these trypanosome lineages. We also confirmed the transcontinental distribution of several trypanosome lineages. Our results show that hippoboscids of several genera are probable vectors of avian trypanosomes.

• Keywords
• Hippoboscidae, Ornithoica, Ornithomya, Ornithophila, Trypanosoma, avian parasite, host specificity, transmission,
• Publication type
• Journal Article MeSH