Crassostrea gigas oysters represent a significant global food source with 4.7 million tons harvested per year. In 2001, the bacterium Vibrio aestuarianus subsp. francensis emerged as a pathogen that causes adult oyster mortality in France and Ireland. Its impact on oyster aquaculture has increased in Europe since its re‐emergence in 2012. To better understand the evolutionary mechanisms leading to the emergence and persistence...

The inadequacy of standard mosquito control strategies calls for ecologically safe novel approaches, for example the use of biological agents such as the endosymbiotic α‐proteobacteria Wolbachia or insect‐specific viruses (ISVs). Understanding the ecological interactions between these “biocontrol endosymbionts” is thus a fundamental step. Wolbachia are transmitted vertically from mother to offspring and modify their hosts’ phe...

Summary Xylella fastidiosa subsp. fastidiosa causes Pierce's disease of grapevine (PD) and has been present in California for over a century. A singly introduced genotype spread across the state causing large outbreaks and damaging the grapevine industry. This study presents 122 X . fastidiosa subsp. fastidiosa genomes from symptomatic grapevines, and explores pathogen genetic diversity associated with PD in California. A tota...

Endosymbiotic Wolbachia bacteria are, to date, considered the most widespread symbionts in arthropods and are the cornerstone of major biological control strategies. Such a high prevalence is based on the ability of Wolbachia to manipulate their hosts' reproduction. One manipulation called cytoplasmic incompatibility (CI) is based on the death of the embryos generated by crosses between infected males and uninfected females or...

Summary Culex pipiens densovirus (CpDV), a single stranded DNA virus, has been isolated from Culex pipiens mosquitoes but differs from other mosquito densoviruses in terms of genome structure and sequence identity. Its transmission from host to host, the nature of its interactions with both its host and host's endosymbiotic bacteria Wolbachia are not known. Here, we report the presence of CpDV in the ovaries and eggs of Cx. pi...

Summary The W olbachia are intracellular endosymbionts widely distributed among invertebrates. These primarily vertically transmitted α‐proteobacteria have been intensively studied during the last decades because of their intriguing interactions with hosts, ranging from reproductive manipulations to mutualism. To optimize their vertical transmission from mother to offspring, the W olbachia have developed fine‐tuned strategies....

Summary The endosymbiont W olbachia pipientis infects various hosts in which it navigates vertically from mothers to offspring. However, horizontal transfers of W olbachia can occur between hosts. The virulence of the horizontally acquired W olbachia can change in the new host as it has been illustrated by the case of the feminizing strain w V ul C from the woodlouse A rmadillidium vulgare that turns to a pathogen when introdu...

Summary The free‐living soil nematode Caenorhabditis elegans interacts with diverse microorganisms in its natural habitat. These microorganisms may serve as a food source or represent a harmful threat. As such, they constitute one of the most important ecological factors of the worm’s natural environment. In this study, we examined the interaction between two natural isolates of C. elegans and three natural isolates of the ent...