Work

A near-complete chromosome from a bacterial pathogen integrated into the genome of its arthropod vector

Year: 2026

Type: preprint

Abstract: Lateral gene transfer (LGT) from organellar to eukaryotic genomes is ubiquitous, resulting in the presence of widespread nuclear mitochondrial DNA segments (NUMTs) and/or plastid gene transfers. While LGT from bacterial associates of eukaryotes is generally less common, many arthropod genomes are littered with LGT originating from Wolbachia (order Rickettsiales) - a vertically transmitted, obligate intracellular symbiont of invertebrates. This contrasts with Rickettsia , a related genus including many important human pathogens, which has not been shown to promulgate LGT within its arthropod vectors. Here, we present the 8.6 Gb genome of a cell line derived from Amblyomma variegatum (the tropical bont tick), which is the primary vector of Rickettsia africae (agent of African tick-bite fever). In addition to numerous NUMTs and diverse families of transposable elements, an almost-complete chromosome of R. africae origin was identified in the cell line genome, localised to the putative sex chromosome. Sequencing of field-collected A. variegatum confirmed the presence of this large LGT in wild ticks, although the absence of transferred genes from the R. africae plasmid provided a means to differentiate LGT from genuine rickettsial infections. These findings highlight the imperative to consider the possibility of LGT when screening vectors for pathogens by PCR.

Source: bioRxiv (Cold Spring Harbor Laboratory)

DOI: 10.64898/2026.09.16.751987