Biology subjects

Tarabai, H.

Publications and source records attributed to Tarabai, H..

4 recordsLinked to original sources

bioRxiv2026

Caught in transition: facultative intracellularity and genome evolution of Symbiopectobacterium in Rhodnius species

Blood-feeding insects typically depend on obligate intracellular bacterial symbionts that provide essential B vitamins absent from vertebrate blood. In contrast, kissing bugs (Triatominae) have long been considered atypical because they rely primarily on extracellular gut-associated bacteria. Recent reports of the genus Symbiopectobacterium in Rhodnius species raise questions about the diversity and evolution of symbiosis in these insects. Here, we investigate the distribution, genome evolution, and tissue localization of Symbiopectobacterium in the genus Rhodnius. Using comparative metagenomics, phylogenomics, fluorescence in situ hybridization, transmission electron microscopy, and hemolymph screening, we characterize a Symbiopectobacterium genome from Rhodnius prolixus and assess its occurrence across publicly available datasets representing multiple Rhodnius species. The R. prolixus strain possesses a large, highly dynamic genome enriched in mobile genetic elements, pseudogenes, and remnants of secretion systems, while retaining biosynthetic pathways for several B vitamins. Comparative analysis revealed variation in genome reduction among Rhodnius-associated strains, suggesting ongoing and potentially independent transitions toward host-restricted symbiosis. Localization analyses detected Symbiopectobacterium intracellularly within posterior midgut epithelial cells and occasionally in the hemolymph, consistent with a facultative intracellular lifestyle. However, no bacteriomes or stable intracellular structures were observed. Together, these findings indicate that Symbiopectobacterium represents an intermediate stage in the transition from environmentally associated bacteria to obligate intracellular mutualists in Triatominae.

microbiology↗

bioRxiv2026

Highly contiguous genomes of Rhodnius prolixus and Triatoma rubida reveal the molecular basis of haematophagy evolution in Triatominae

Insects of the subfamily Triatominae, commonly known as kissing bugs, are obligate blood-feeding vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Rhodnius prolixus is among the most epidemiologically important vectors in Latin America, whereas Triatoma rubida frequently invades homes and is a potential vector in the southern United States and northern Mexico. Triatomines likely evolved from predatory reduviid assassin bugs through a transition from feeding on arthropods associated with vertebrate hosts to feeding directly on vertebrate blood. To investigate the genomic basis of this ecological and dietary shift, we generated highly contiguous, near chromosome-level genome assemblies and structural gene annotations for R. prolixus and T. rubida. The new R. prolixus assembly improves scaffold N50 more than 40-fold over the current reference genome, from 1.1 to 43.9 Mb, while reducing assembly gaps by several orders of magnitude. Both assemblies exceed 97% BUSCO completeness. Comparative analyses with representative hemipteran genomes revealed expansions of gene families associated with chemosensation and metabolism, including detoxification, protein degradation, and digestion, together with signatures of positive selection in genes involved in digestive and sensory functions. These assemblies represent the most contiguous and complete genomic resources available for Triatominae and provide a robust foundation for investigating vector biology, host adaptation, and the evolutionary origins of blood feeding within Reduviidae. Interpretive summaryKissing bugs are insects that are known for feeding on blood. They can spread a disease called Chagas disease because they transmit a parasite called Trypanosoma cruzi. To understand how kissing bugs evolved and which genes facilitate blood feeding of vertebrates, a collaboration between scientists at USDA-ARS, University of Georgia, and University of South Bohemia sequenced the genome of two kissing bugs: Rhodnius prolixus and Triatoma rubida. By comparing the genes with those of other insects in the order Hemiptera, scientists discovered that kissing bugs have more genes involved with detecting environmental chemical stimuli and metabolism as well as positive selection for genes involved with digestion and sensory-related proteins. These genome assemblies will help scientists learn more about how these insects evolved, and this research is important for understanding insect feeding biology which can be used to develop methods to control the kissing bugs and the spread of Chagas disease.

evolutionary biology↗

bioRxiv2023

Highly resolved genomes as a tool for studying speciation history of two closely related louse lineages with different host specificities.

Sucking lice of the suborder Anoplura are permanent ectoparasites with specific lifestyle and highly derived features. Currently, genomic data are only available for a single species, the human louse Pediculus humanus. In this study we present genomes of two distinct lineages, with different host spectra, of a rodent louse Polyplax serrata. Genomes of these ecologically different lineages are closely similar in gene content, display a high level of synteny, but they also differ by a few duplications/translocations and single inversion. Compared to P. humanus, the two P. serrata genomes are noticeably larger (139 Mbp vs. 111 Mbp) and encode a higher number of genes. Similar to P. humanus, they are significantly reduced in sensory-related categories such as vision and olfaction. Utilizing a genome-wide set of genes, we perform phylogenetic reconstruction and evolutionary dating of the P. serrata lineages. Obtained estimates reveal their relatively deep origin (approx. 6.5 Mya), comparable to the time of split between the human and chimpanzee lice Pediculus humanus and P. schaeffi. This dating supports the view that the P. serrata lineages are likely to represent two cryptic species with different host spectra. Historical demographies of the two lineages show glaciation-related population size (Ne) reduction, but recent restoration of Ne was seen only in the less host specific lineage. Together with the louse genomes, we analyze genomes of their bacterial symbiont Legionella polyplacis, and evaluate their potential complementarity in synthesis of amino acids and B vitamins. We show that both systems, Polyplax/Legionella and Pediculus/Riesia, display almost identical patterns, with symbionts involved in synthesis of B vitamins but not amino acids.

genomics↗

bioRxiv2023

Microbiomes of blood feeding triatomines in the context of their predatory relatives and the environment

AbstractThe importance of gut microbiomes has become generally recognized in vector biology. This study addresses microbiome signatures in North American Triatoma species of public health significance (vectors of Trypanosoma cruzi) linked to their blood feeding strategy and the natural habitat. To place the Triatoma associated microbiomes within a complex evolutionary and ecological context, we sampled sympatric Triatoma populations, related predatory reduviids, unrelated ticks, and environmental material from vertebrate nests where these arthropods reside. Along with five Triatoma species, we have characterized microbiomes of five reduviids (Stenolemoides arizonensis, Ploiaria hirticornis, Zelus longipes, and two Reduvius species), a single soft tick species, Ornithodoros turicata, and environmental microbiomes from selected sites in Arizona, Texas, Florida and Georgia. The microbiomes of predatory reduviids lack a shared core microbiota. Like in triatomines, microbiome dissimilarities among species corelate with dominance of a single bacterial taxa. These include Rickettsia, Lactobacillus, Candidatus Midichloria, and Zymobacter, which are often accompanied by known symbiotic genera, i.e., Wolbachia, Candidatus Lariskella, Asaia, Gilliamella, and Burkholderia. We have further identified compositional convergence of analyzed microbiomes in respect to the host phylogenetic distance in both blood feeding and predatory reduviids. While microbiomes of two reduviid species from Emesinae family reflect their close relationship, the microbiomes of all Triatoma species repeatedly form a distinct monophyletic cluster highlighting their phylosymbiosis. Furthermore, based on environmental microbiome profiles and blood meal analysis, we propose three epidemiologically relevant and mutually interrelated bacterial sources for Triatoma microbiomes, i.e., host abiotic environment, host skin microbiome, and pathogens circulating in host blood. ImportanceThis study places microbiomes of blood feeding North American Triatoma vectors (Reduviidae) into a broader evolutionary and ecological context provided by related predatory assassin bugs (Reduviidae), another unrelated vector species (soft tick Ornithodor turicata), and the environment these arthropods cohabit. For both vectors, microbiome analyses suggest three interrelated sources of bacteria, i.e., microbiome of vertebrate nests as their natural habitat, vertebrate skin microbiome, and pathobiome circulating in vertebrate blood. Despite an apparent influx of environment-associated bacteria into the arthropod microbiomes, Triatoma microbiomes retain their specificity, forming a distinct cluster that significantly differ from both predatory relatives and ecologically comparable ticks. Similarly, within the related predatory Reduviidae, we found the host phylogenetic distance to underlie microbiome similarities.

ecology↗