Biology subjects

Misson, P.

Publications and source records attributed to Misson, P..

4 recordsLinked to original sources

bioRxiv2026

A Bactericidal Phospholipase from Archaea

Archaea kill bacteria, at least on occasion. The molecular underpinnings of these lethal interactions are barely understood. Here, we describe cinquedea, an /{beta} hydrolase secreted by the halophilic archaeon Haloferax larsenii s5a-1. Cinquedea exhibits bactericidal activity in the nanomolar range, killing halophilic Pontibacillus bacteria. Bacterial death is accompanied by gross morphological abnormalities, indicative of severe damage to the cell envelope. We predict, and confirm in vitro, that cinquedea is a phospholipase, with structural similarities to a phospholipase A1 enzyme isolated from hornet venom. Exposing lipids extracted from a cinquedea-sensitive Pontibacillus strain to the enzyme leads to accumulation of lysophosphatidylglycerol, a cleavage product of phospholipase A activity. This is consistent with direct activity of cinquedea against the Pontibacillus membrane, which we show is chiefly composed of phosphatidylglycerol. Considered alongside recent findings that some archaea encode bactericidal peptidoglycan hydrolases, these results suggest that archaea can kill bacteria in mechanistically diverse ways. Our work provides a template for future experimental discovery and characterization of bactericidal proteins of archaeal origin and reinforces an emerging view that archaea represent a substantial reservoir for the discovery of new antibacterial compounds.

microbiology↗

bioRxiv2025

Bacteriophage PAK_P3 genome structuration and dynamics during infection of Pseudomonas aeruginosa reveal specific interactions patterns

Bacteriophages, or phages, are highly abundant and diverse genomic entities that play an important role in microbial ecology, evolution, and horizontal gene transfer. While the dynamic changes in genome organization in cellular organisms have been well described, the 3D folding of phage genomes during the infection of their host is extremely limited. Understanding how phage genomes fold, invade and rearrange the genome of their host to functionally organize the optimal expression of their genes remains unknown. Here, we explore the spatial dynamics of the virulent double-stranded DNA phage PAK_P3 during infection of its host Pseudomonas aeruginosa and reveal how its genome rapidly decondenses to adopt a specific 3D organization that reflects its transcriptional program. Concomitantly, the host genome decondenses as gene expression wanes and transcription induced domains vanish. We also uncover specific and discrete bridging of the host and the phage genomes, showing how the phage genome exploits the spatial genome architecture of its host to succeed in its infection cycle. Our data highlights an unprecedented level of genome folding and gene expression regulation during a viral infection.

microbiology↗

bioRxiv2023

Phage-mediated dispersal of multicellular bacteria

Streptomyces are renowned for their prolific production of specialized metabolites with applications in medicine and agriculture. These multicellular bacteria present a sophisticated developmental cycle, and play a key role in soil ecology. Little is known about Streptomyces-phage interactions and the impact of phages on Streptomyces physiology. In this study, we investigated the conditions governing the expression and production of Samy, a prophage found in Streptomyces ambofaciens ATCC 23877. This siphoprophage is produced simultaneously with the activation of other mobile genetic elements. We show that Samy production increases bacterial dispersal under in vitro stress conditions. Altogether, we unveiled a new property of a bacteriophage infection that it is closely linked to the multicellular community life of Streptomyces bacteria. Graphical summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/549817v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@126b3fcorg.highwire.dtl.DTLVardef@1f26808org.highwire.dtl.DTLVardef@18bfdcforg.highwire.dtl.DTLVardef@1c44be3_HPS_FORMAT_FIGEXP M_FIG C_FIG IMPORTANCEStreptomyces are multicellular bacteria producing valuable metabolites, including antibiotics, with applications in medicine and agriculture. In this study, we characterized a novel temperate phage, named Samy, and its impact on bacteria physiology. Remarkably, the presence and production of Samy increases bacterial dispersal under in vitro stress conditions. This constitutes an emerging property associated with bacteriophage infection that might enhance the spread of the species. Our study reveals a new aspect of bacteriophage infection in the context of multicellular aggregate dynamics.

microbiology↗

bioRxiv2022

Prophage taming by the adherent-invasive Escherichia coli LF82 upon macrophage infection

Adherent-invasive Escherichia coli (AIEC) strains are frequently recovered from stools of patients with dysbiotic microbiota. They have remarkable properties of adherence to the intestinal epithelium, and survive better than other E. coli in macrophages. The best studied of these AIEC is probably strain LF82, which was isolated from a Crohns disease patient. This strain contains five complete prophages, which have not been studied until now. We undertook their analysis, both in vitro and inside macrophages, and show that all of them form virions. The Gally prophage is by far the most active, generating spontaneously over 108 viral particles per mL of culture supernatants in vitro, more than 100-fold higher than the other phages. Gally is over-induced after a genotoxic stress generated by ciprofloxacin and trimethoprim. However, upon macrophage infection, Gally virion production is decreased by more than 20-fold, and the transcription profile of the prophage indicates that part of the structural module is specifically repressed while the replication module is overexpressed compared to unstressed culture conditions. We conclude that strain LF82 has evolved an efficient way to "tame" its most active prophage upon macrophage infection, which may participate to its good survival in macrophages. The results are discussed in light of the active lysogeny process. AUTHOR SUMMARYProphages are bacterial viruses stably integrated into their host, to which they can provide new functions, thus increasing their fitness in the environment. Thereby, they can participate to the virulence of bacterial pathogens. However, prophages are double-edged swords that can be awakened in response to genotoxic stresses, resulting in the death of their bacterial host. This raises the question of the effect of this type of stress in the natural environments where their bacterial hosts exert their virulence. In this study, we characterized the five active prophages present in Escherichia coli LF82, a strain belonging to the intestinal microbiota and suspected to be involved in Crohns disease via its ability to invade macrophages, a highly genotoxic environment. We show that LF82 inhibits the awakening of its prophages in macrophages, allowing it to survive there. Moreover, deletion of its most active prophage does not affect the viability of LF82 in this environment. These results show that LF82 has tamed its prophages in macrophages and also suggest that if they convey fitness advantages, they probably do so in environments differing from macrophages, and which remain to be discovered.

microbiology↗