Biology subjects

Amoros, J.

Publications and source records attributed to Amoros, J..

3 recordsLinked to original sources

bioRxiv2026

Characterisation and genomic analysis of bacterial nutritional endosymbionts in Australian ticks from shotgun metagenomic sequencing

Ticks are obligate hematophagous arthropods and feed exclusively on blood. As blood is nutrient-poor, ticks rely on bacterial endosymbionts to synthesise nutrients, yet the diversity and functional roles of these symbionts in Australian ticks remain largely uncharacterised. This is critical to address as these ticks are of high medical importance in Australia. In this study, shotgun metagenomic sequencing was performed on Bothriocroton concolor, Bothriocroton hydrosauri, Haemaphysalis longicornis and Ixodes holocyclus, enabling the recovery of six complete or partial metagenome-assembled genomes (MAGs). These comprised Coxiella-like endosymbionts (CLE), a facultative Rickettsia symbiont, and two Midichloria mitochondrii strains (Ixholo1 and Ixholo2). Functional annotation of these taxon-specific symbionts revealed the absence of virulence factors and the presence of B-vitamin and/or heme biosynthesis genes, indicative of nutritional mutualism, which is essential for tick hematophagy. The CLEs additionally harbour genes of the shikimate pathway, which modulate blood feeding in ticks by regulating serotonin biosynthesis. Furthermore, functional annotation and pangenomic analysis of Midichloria spp. found evidence that the genus may encompass multiple species, as well as the retention of genes potentially associated with an intramitochondrial lifestyle in M. mitochondrii Ixholo2. Tick microbiomes are dominated by non-pathogenic microorganisms, which are often overshadowed by pathogens. These include the endosymbionts, which can influence host biology and pathogen transmission, and are fundamental for the development of diagnostic tools and taxon-specific tick biocontrols.

microbiology↗

bioRxiv2025

Genomic Islands in Wolbachia Prophages Drive Amplification andDiversification of Cytoplasmic Incompatibility Genes in Culex pipiens

Wolbachia are maternally inherited endosymbiotic bacteria widespread among arthropods. They manipulate their host reproduction to enhance their prevalence in host populations. The most common manipulation is cytoplasmic incompatibility (CI), causing embryonic death in crosses between infected males and uninfected females, or between individuals carrying distinct incompatible Wolbachia. CI patterns are highly complex in the mosquito Culex pipiens, where the causal genes cidA and cidB are amplified and diversified, forming a "cid repertoire" within each Wolbachia wPip genome. Despite their central role in CI, the genomic mechanisms underlying such cid amplification and diversification remained poorly understood. This knowledge gap is largely due to the difficulty of assembling wPips genomes due to highly repeated genes and mobile elements, especially in WO prophages. Here, we directly annotated Illumina polished Nanopore-sequences to investigate the genomic flanking context of cid genes in three distinct wPip lineages. We assembled WO prophage regions of substantial length containing the entire cid repertoire previously described in these bacterial lineages. Within these WO regions, cid genes are consistently embedded in modular and rearrangeable islands composed of MutL, rnhA, and small mobile elements, all displaying hyperconserved nucleotide identity across islands. These genomic islands are probably drivers for major rearrangement and recombination events responsible for the amplification and diversification of cidwPip genes within and between the wPip genomes leading to CI complexity in C. pipiens.

evolutionary biology↗

bioRxiv2024

Comparative genomics of Rickettsiella bacteria reveal variable metabolic traits involved in symbiotic interactions with arthropods

Members of the Rickettsiella genus (order: Legionellales) are emerging as widespread bacteria associated with insects, arachnids, and crustaceans. While some Rickettsiella strains are highly virulent pathogens, others are maternally inherited endosymbionts that manipulate arthropod phenotypes, including the induction of defensive symbiosis and cytoplasmic incompatibility. However, the genomic diversity of Rickettsiella remains largely unexplored, and their genetic potential to induce complex phenotypes in arthropods is only partially understood. In this study, we sequenced five new Rickettsiella genomes isolated from three tick species. Through comparative genomics, we observed that Rickettsiella members share similar metabolic capabilities, and collectively lack virulence genes from pathogenic Legionellales. Additional analysis of Rickettsiella genomes revealed significant variability in metabolic properties related to endosymbiosis. Specifically, their capacity to biosynthesize certain B vitamins and heme varies, suggesting a functional role of some Rickettsiella strains in the nutrition of their arthropod hosts. Some Rickettsiella genomes harbour homologs of Wolbachia cif genes, the cause of Wolbachia-induced cytoplasmic incompatibility,, suggesting that Rickettsiella may use a similar molecular mechanism to manipulate the reproduction of their arthropod hosts. Phylogenomics further revealed that tick-borne Rickettsiella exhibit distinct evolutionary origins within the genus, indicating that Rickettsiella have undergone repeated horizontal transfers between ticks and other arthropods.

evolutionary biology↗