Biology subjects

Rihova, J.

Publications and source records attributed to Rihova, J..

4 recordsLinked to original sources

bioRxiv2024

An obligate symbiont of Haematomyzus elephantis with a strongly reduced genome resembles symbiotic bacteria in sucking lice

The parvorder Rhynchophthirina with a single genus Haematomyzus is a small group of ectoparasites related to sucking and chewing lice. Previous screening based on the 16S rRNA gene indicated that Haematomyzus harbour a symbiotic bacterium whose DNA exhibits a strong shift in nucleotide composition typical of obligate mutualistic symbionts in insects. Within Phthiraptera, the most dramatically reduced genomes are found in the symbionts associated with sucking lice, living exclusively on mammal blood, compared to the less modified symbionts inhabiting the chewing lice, which feed on skin derivates. In this study, we investigate the genome characteristics of the symbiont associated with Haematomyzus elephantis. We sequenced and assembled the Haematomyzus elephantis metagenome, extracted a genome draft of its symbiotic bacterium, and show 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, such as mammals blood versus 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 are not known. In this study, we assemble genome of symbiotic bacterium from Haematomyzus elphantis (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 louse symbionts, it retains essential pathways for the synthesis of several B vitamins.

genomics↗

bioRxiv2023

Arsenophonus symbiosis with louse flies: multiple origins, coevolutionary dynamics, and metabolic significance

Arsenophonus is a widespread insect symbiont with life strategies that vary from parasitism to obligate mutualism. In insects living exclusively on vertebrate blood, mutualistic Arsenophonus strains are presumed to provide B vitamins missing in the insect host diet. Hippoboscidae, obligate blood-feeders related to tsetse flies, were previously suggested to have acquired Arsenophonus symbionts in several independent events. Based on comparative genomic analyzes of eleven Hippoboscidae-associated strains, nine of them newly assembled, we reveal a wide range of their genomic characteristics and phylogenetic affiliations. Phylogenetic patterns and genomic traits split the strains into two different types. Seven strains display characteristics of obligate mutualists with significantly reduced genomes and long phylogenetic branches. The remaining four genomes cluster on short branches, and their genomes resemble those of free-living bacteria or facultative symbionts. Both phylogenetic positions and genomic traits indicate that evolutionary history of the Hippoboscidae-Arsenophonus associations is a mixture of short-term coevolutions with at least four independent origins. The comparative approach to a reconstruction of B vitamin pathways across the available Arsenophonus genomes produced two kinds of patterns. On one hand, it indicated the different importance of individual B vitamins in the host-symbiont interaction. While some (riboflavin, pantothenate, folate) seem to be synthesized by all Hippoboscidae-associated obligate symbionts, pathways for others (thiamine, nicotinamide, cobalamin) are mostly missing. On the other hand, the broad comparison produced patterns which can serve as bases for further assessments of the pathways completeness and functionality. ImportanceInsects 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 eleven 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 two-fold. 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.

evolutionary biology↗

bioRxiv2019

A new symbiotic lineage related to Neisseria and Snodgrassella arises from the dynamic and diverse microbiomes in sucking lice

Phylogenetic diversity of symbiotic bacteria in sucking lice suggests that lice have experienced a complex history of symbiont acquisition, loss, and replacement during their evolution. By combining metagenomics and amplicon screening across several populations of two louse genera (Polyplax and Hoplopleura) we describe a novel louse symbiont lineage related to Neisseria and Snodgrassella, and show its independent origin within dynamic lice microbiomes. While the genomes of these symbionts are highly similar in both lice genera, their respective distributions and status within lice microbiomes indicate that they have different functions and history. In Hoplopleura acanthopus, the Neisseria-related bacterium is a dominant obligate symbiont universally present across several hosts populations, and seems to be replacing a presumably older and more degenerated obligate symbiont. In contrast, the Polyplax microbiomes are dominated by the obligate symbiont Legionella polyplacis, with the Neisseria-related bacterium co-occurring only in some samples and with much lower abundance.

evolutionary biology↗

bioRxiv2017

Legionella becoming a mutualist: adaptive processes shaping the genome of symbiont in the louse Polyplax serrata

Legionellaceae are intracellular bacteria known as important pathogens of man. In the environment, they are mainly found in biofilms associated with amoebas. In contrast to another gammaproteobacterial family Enterobacteriaceae which established a broad spectrum of symbioses with many insect taxa, the only instance of legionella-like symbiont has been reported from lice of the genus Polyplax. Here, we sequenced the complete genome of this symbiont and compared its main characteristics to other Legionella species and insect symbionts. Based on rigorous multigene phylogenetic analyses, we confirm this bacterium as a member of the genus Legionella and propose the name Candidatus Legionella polyplacis, sp.n. We show that the genome of Ca. Legionella polyplacis underwent massive degeneration, including considerable size reduction (529.746 bp, 484 protein coding genes) and a severe decrease in GC content (23%). We identify several possible constraints underlying the evolution of this bacterium. On one hand, Ca. Legionella polyplacis and the louse symbionts Riesia and Puchtella experienced convergent evolution, perhaps due to adaptation to similar hosts. On the other hand, some metabolic differences are likely to reflect different phylogenetic positions of the symbionts and hence availability of particular metabolic function in the ancestor. This is exemplified by different arrangements of thiamine metabolism in Ca. Legionella polyplacis and Riesia. Finally, horizontal gene transfer is shown to play a significant role in the adaptive and diversification process. Particularly, we show that Ca. L. polyplacis horizontally acquired a complete biotin operon (bioADCHFB) that likely assisted this bacterium when becoming an obligate mutualist.

evolutionary biology↗