Biology subjects

Comte, G.

Publications and source records attributed to Comte, G..

3 recordsLinked to original sources

bioRxiv2026

Multifaceted roles of extracellular vesicles in Agrobacterium fabrum C58 lifestyles

Bacterial extracellular vesicles (EVs) constitute a key driver of interspecies and inter-kingdom communication, and shape bacterial ecology, yet their role as a dynamic delivery system remains underexplored. Here, we show that the plant pathogen Agrobacterium fabrum C58 modulates its EVs in response to virulence-inducing conditions. Our multi-omics analysis revealed that these virulence-state EVs are significantly enriched in effectors from the Type IV secretion system and toxins from the Type VI secretion system, which were previously known to be delivered by conventional contact-dependent mechanisms. We demonstrate that these EVs can directly transfer virulence effectors into plant host cells, enhancing tumor formation. Furthermore, we show that these EVs can interact with and influence the development of several environmental bacteria. Finally, A. fabrum C58 EVs elicit distinct plant host metabolome responses compared to whole cells. Our findings establish EVs as a crucial and dynamic component of bacterial virulence and inter-kingdom communication, providing a new perspective on how bacteria adapt to and manipulate their environment.

microbiology↗

bioRxiv2025

Extracellular vesicles of a phytobeneficial bacterium trigger distinct systemic response in plant

Bacterial extracellular vesicles (EVs) are lipidic shuttles that play roles in virulence, inter-species competition, and in the induction of the host immune response. While they have primarily been investigated in animal-bacteria interactions, knowledge regarding phytobacterial EVs remains limited. Recent findings revealed that various biotic factors like hydroxycinnamic acids can regulate EVs production. Hydroxycinnamic acids, such as ferulic acid, are lignin components abundantly released in the plant environment, where they impact the ecology of numerous phytobacteria. Azospirillum sp. B510, a phytobeneficial bacterium, induces the accumulation of hydroxycinnamic acid derivatives in the plant and can metabolize them as carbon sources. We hypothesized that the presence of ferulic acid in the environment of Azospirillum sp. B510 would influence its EVs production in terms of size, quantity, and cargo. Conversely, we also proposed that EVs from this phytobacterium would influence plant metabolites and defense gene expression. Our results show both that ferulic acid (mimicking the plant environment) influences the content of EVs released by Azospirillum sp. B510 and that bacterial EVs also impact plant physiology at a systemic level according to their cargoes. This research provides the first evidence of a global effect of bacterial EVs on the plant and highlights the dynamics of plant-bacteria interactions mediated by EVs.

microbiology↗

bioRxiv2024

Phenolic compounds in Medicago truncatula roots are under the influence of Agrobacterium fabrum through its species specific-genes regions

The impact of plant microbiota on the health and physiology of their host is increasingly studied and recognized. However, in the rhizosphere, the functions of most bacteria and the genetic determinants involved in the molecular dialogue between plant and bacteria are poorly understood. Agrobacteria are ubiquitous soil borne and rhizospheric bacteria able to establish commensal or even beneficial interactions with plant roots. The genomic species Agrobacterium fabrum harbor seven specific-regions (SpG8-1 to SpG8-7), whose annotation seems to indicate a close connection with the plant during plant-bacteria interactions. To evaluate the involvement of A. fabrum-specific regions in the plant-bacteria interaction, deletion mutant strains of each A. fabrum-specific region were inoculated on Medicago truncatula roots. Root metabolite profiles were compared by UHPLC-UV/DAD-ESI-MS QTOF analyses, and the highlighted discriminating metabolites were annotated by tandem mass spectrometry. Metabolomic analyses have shown that A. fabrum inoculation modulates the content of phenolic compounds in M. truncatula roots, in particular flavonoids. These root metabolite modulations observed with the wild-type strain often appear to be linked to at least one of the A. fabrum-specific genes, as almost all A. fabrum-specific regions showed an influence on one or more of these specialized root metabolites. In addition, our results underlined a putative cross-talk or coordinated effect of the A. fabrum-specific regions during the interaction of A. fabrum with M. truncatula, as all mutants except one induced similar modifications on flavonoids. These results contribute to a better understanding of the ecological niche construction of A. fabrum highlighting the importance of its specific genes in the establishment of this fine-tuned interaction.

ecology↗