Biology subjects

Poussier, S.

Publications and source records attributed to Poussier, S..

2 recordsLinked to original sources

bioRxiv2024

Emergence and host range expansion of an epidemic lineage of Ralstonia solanacearum

The evolutionary processes underlying disease outbreaks remain unknown for most bacterial plant pathogens. We sequenced an outbreak of lethal wilt disease in Martinique caused by two distantly related lineages in the Ralstonia solanacearum species complex. One lineage (R. solanacearum IIB-4NPB) exhibited the broadest host range ever documented for a single lineage in the field, while the other (R. pseudosolanacearum I-18) expanded in parallel but retained specialisation on solanaceaous hosts. Phylogenomic analysis of 407 outbreak isolates shows both lineages independently disseminated from mainland populations into Martinique. We resolved fine-scale geographic patterns of genomic diversity and identified spatial hotspots of interspecies mobile element exchange, resulting in the identification of a new family of Ralstonia integrative conjugative elements (ICEs) associated with the outbreak. ICE accessory gene integration sites display striking functional specialization and differentiation despite variable gene content: each site acquires only metabolism-associated or defence-related genes, respectively. This work provides insight into the origin and genomic changes associated with an outbreak of plant disease, and highlights the role of mobile elements in driving pathogen emergence.

microbiology↗

bioRxiv2024

A phylogenetic host range index reveals contrasted relationships between phage virulence and specialisation

Phages are typically known for having a limited host range, targeting various strains within a specific bacterial species. However, factors like the phylogeny or epidemiology of host bacteria are often disregarded, despite their potential influence on phage specialization and virulence. This research utilizes a new "phylogenetic host range index" that accounts for the genetic diversity of bacterial hosts, to classify phages into specialists and generalists accurately. We provide evidence that the CRISPR-Cas immune system of bacteria more frequently targets generalist phages than specialist phages. We explore the hypothesis that generalist phages might exhibit lower virulence than specialist ones due to potential evolutionary trade-offs between host range breadth and virulence. Importantly, contrasted correlations between phage virulence and host range depend on the epidemiological context. A trade-off was confirmed in a homogeneous bacterial epidemiology situation, but not in more complex epidemiological scenario, where no apparent costs were detected for phages adapted to a wide range of hosts. This study highlights the need for genetic analyses in phage host range and of investigating ecological trade-offs that could improve their applications in biocontrol or therapy.

microbiology↗