Evolution of increased virulence is associated with decreased spite in the insect-pathogenic bacterium Xenorhabdus nematophila

Abstract

Disease virulence may be strongly influenced by social interactions among pathogens, both during the time course of an infection and evolutionarily. Here, we examine how spiteful bacteriocin production in the insect-pathogenic bacterium Xenorhabdus nematophila is evolutionarily linked to its virulence. We expected a negative correlation between virulence and spite owing to their inverse correlations with growth. We examined bacteriocin production and growth across 14 experimentally evolved lineages that show faster host-killing relative to their ancestral population. Consistent with expectations, these more virulent lineages showed reduced bacteriocin production and faster growth relative to the ancestor. Further, bacteriocin production was negatively correlated with growth across the examined lineages. These results strongly support an evolutionary trade-off between virulence and bacteriocin production and lend credence to the view that disease management can be improved by exploiting pathogen social interactions.

Facilitative priority effects drive parasite assembly under coinfection

“…In light of this diversity, it is not surprising that host individuals are often infected with diverse parasite assemblages, composed of multiple parasite species or multiple genetic variants ('strains') of the same species (Mideo 2009;Greischar et al 2020). Within hosts, interactions among coinfecting parasite strains can influence the dynamics of drug resistance (Wale et al 2017), evolution of virulence (Bhattacharya et al 2019), and the magnitude of parasite epidemics (Susi et al 2015), with implications for host health (Read & Taylor 2001). Thus, understanding how parasite strains interact in shared host individuals may be important for predicting the spread of infectious diseases and ameliorating their impact on host populations.…”

Post‐association barrier to host switching maintained despite strong selection in a novel mutualism

“…Large population sizes within the insect (nematodes >10 4 , bacteria >10 6 ) allow for mutational input to occur in both species. Indeed, previous studies have shown that some Xenorhabdus traits (e.g., growth rate and bacteriocin production) can evolve when passaged with nematodes in the lab (Bhattacharya et al, 2019 ; Morran et al, 2016 ). However, it is possible that adaptation to new partners requires multiple mutations, which would constrain the speed of evolutionary rescue.…”

Evolution and taxonomy of nematode-associated entomopathogenic bacteria of the genera Xenorhabdus and Photorhabdus: an overview

“…However, under the selective pressure of maintenance of long-term mutualistic interactions with the nematodes host, two separate genera of bacteria displaying host specific associations have evolved (Boemare 2002;Chaston et al 2011). Studies have also revealed that a general trend in the EPN bacterial phylogeny is the increasing virulence associated with evolutionary trade-off between virulence and bacteriocin production abilities (Blackburn et al 2016;Meli and Bashey 2018;Bhattacharya et al 2019).…”