Biology subjects

Demarre, G.

Publications and source records attributed to Demarre, G..

4 recordsLinked to original sources

bioRxiv2025

Complementary killing activities of Pbunavirus LS1 and Bruynoghevirus LUZ24 phages on planktonic and sessile Pseudomonas aeruginosa PAO1 derivatives

Four P. aeruginosa phages active against a representative panel of strains, and with complementary spectra of action were chosen with the goal of using them for phage therapy. Two of them were myoviruses belonging to the Pbunavirus LS1 species, and two were podoviruses belonging to the Bruynoghevirus LUZ24 species. In order to better apprehend the interactions of these phages with their P. aeruginosa host bacteria, we undertook the characterization of their bacterial receptors, using a PAO1 derivative as a recipient strain. Whereas the receptor of the P. LS1 phage Ab27 had already been characterized as the O-antigen chain of the lipopolysaccharides, no information was available at the onset of this work on the receptor used by the phages of the B. LUZ24 species. We show that the surface polysaccharide Psl is this receptor. Psl stands for polysaccharide synthesis locus, and it is an important component of the biofilm matrix in a large panel of P. aeruginosa strains, including PAO1. Remarkably, the B. LUZ24 phages were more active against PAO1 in minimal medium compared to rich medium. Consistently, this was correlated with larger amounts of Psl bound at the bacterial surface during exponential growth in the minimal medium compared to the rich medium. Biofilms formed on a medical intubation device, as well as in in 96-well plates, were degraded to different extent by the two phage species: biofilms grown for 7 hours on tubing device were degraded more efficiently by the B. LUZ24 than the P. LS1 phage, whereas mature biofilms (16 hours) formed in 96-well plates were degraded more rapidly by P. LS1 than by B. LUZ24 phage. The frequency of genetic mutants resisting to each phage were determined in liquid medium by a fluctuation assay and found in the range of 10-5 to 10-6 per generation. Interestingly, most of the P. LS1 resisting mutants were more sensitive to the B. LUZ24 phage. We conclude that the combination of the four selected phages has very promising properties, which should be relevant in the framework of phage therapy.

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↗

bioRxiv2020

The Crohn's disease-related AIEC strain LF82 assembles a biofilm-like matrix to protect intracellular microcolonies from phagolysosomal attack

Patients with Crohns disease exhibit abnormal colonization of the intestine by proteobacteria, and among these bacteria, the adherent invasive E. coli (AIEC) family. They are predominant in the mucus, adhere to epithelial cells, colonize them and survive inside macrophages. We recently demonstrated that the acclimation of the AIEC strain LF82 to phagolysosomal stress requires stringent and SOS responses. Such adaptation involves a long lag phase in which many LF82 cells become antibiotic tolerant. Later during infection, they proliferate in vacuoles and form colonies harboring dozens of LF82 bacteria. In the present work, we investigated the mechanism sustaining this phase of growth. We found that intracellular LF82 produced an extrabacterial matrix composed of exopolysaccharides and amyloid fibers that surrounded each individual LF82 cell. This matrix acts as a biofilm and controls the formation of LF82 intracellular bacterial communities (IBCs) inside phagolysosomes for several days post infection. Using genomics assays, we characterized the gene set involved in IBCs formation and revealed the crucial role played by a pathogenicity island presents in the genome of most AIEC strains in this process. Iron capture, by the yersiniabactin system encoded by this pathogenicity island, is essential to form IBC and LF82 survival within macrophages. These results demonstrate that AIEC have developed a sophisticated strategy to establish their replicative niche within macrophages, which might have implications for envisioning future antibacterial strategies for Crohns disease.

microbiology↗

bioRxiv2019

Intracellular AIEC LF82 relies on SOS and stringent responses to survive, multiply and tolerate antibiotics.

Adherent Invasive Escherichia coli (AIEC) strains recovered from Crohn's disease lesions survive and multiply within macrophages. A reference strain for this pathovar, AIEC LF82, forms microcolonies within phagolysosomes, an environment that prevents commensal E. coli multiplication. Little is known about the LF82 intracellular growth status, and signals leading to macrophage intra-vacuolar multiplication. We used single-cell analysis, genetic dissection and mathematical models to monitor the growth status and cell cycle regulation of intracellular LF82. We found that within macrophages, bacteria may replicate or undergo non-growing phenotypic switches. This switch results from stringent response firing immediately after uptake by macrophages or at later stages, following genotoxic damage and SOS induction during intracellular replication. Importantly, non-growers resist treatment with various antibiotics. Thus, intracellular challenges induce AIEC LF82 phenotypic heterogeneity and non-growing bacteria that could provide a reservoir for antibiotic-tolerant bacteria responsible for relapsing infections.

microbiology↗