Biology subjects

De Sordi, L.

Publications and source records attributed to De Sordi, L..

5 recordsLinked to original sources

bioRxiv2024

Differential translocation of bacteriophages across the intestinal barrier in health and Crohn's disease

Impaired intestinal barrier function is a major feature of Crohns disease (CD), leading to exacerbated inflammation in response to the microbiota. In this context, the translocation of intestinal bacteriophages (phages) and their effects on the host have been little investigated. We used phage fluorescence imaging coupled with ex-vivo and in-vitro models that mimic physiological and inflammatory conditions and found that phages can translocate across the intestinal barrier without disrupting its integrity. Although the translocation rate across the intestinal epithelium depended on phage morphology and the condition of the barrier, these factors did not influence the crossing of phage across the vascular endothelium. Virome analysis confirmed that viral sequences shared between blood and stool samples are more abundant in CD patients than healthy subjects, indicating that a barrier defect facilitates phage translocation from the gut to the bloodstream.

cell biology↗

bioRxiv2024

The human blood harbors a phageome which differs in Crohn's disease

Increasing evidence suggests that the human blood hosts microbes including bacteria and eukaryotic viruses, which could have important implications for health. Bacteriophages of the blood are challenging to study and have been overlooked, but could translocate to this environment from different body-sites. We thus developed specific virome protocols and analysis methods to study the viral communities of blood samples obtained from healthy individuals and Crohns disease (CD) patients. We uncovered a diverse viral community in the human blood, dominated by phages infecting Pseudomonadota bacteria. We found that an important fraction of those phages overlaps with the gut virome, consolidating the idea that gut phages can translocate to the blood. Strikingly, viral communities of the blood were different between CD patients and healthy individuals, revealing a new signature of disease. This was not the case for fecal viral communities. Collectively, these results advance our knowledge of the microorganisms present in the human blood and pave the way for further studies of this environment in the context of disease.

microbiology↗

bioRxiv2022

An alternative method to multiple displacement amplification for preparing virome DNA in a way adapted for the sequencing of both double-strand and single-strand DNA viruses

Background: Bulk microbiome, as well as virome-enriched shotgun sequencing only reveals the double-stranded DNA (dsDNA) content of a given sample, unless specific treatments are applied. However, genomes of viruses often consist of a circular single-stranded DNA (ssDNA) molecule. Pre- treatment and amplification of DNA using the multiple displacement amplification (MDA) method enables conversion of ssDNA to dsDNA, but this process can lead to over-representation of these circular ssDNA genomes. A more recent alternative permits to bypass the amplification step, as library adapters are ligated to sheared and denatured DNA, after an end-modification step (xGen kit). However, the sonication step might shear ssDNA more efficiently than dsDNA, therefore introducing another bias in virome sequencing. These limitations prompted us to explore an alternative method of DNA preparation for sequencing mixed ssDNA and dsDNA viromes. Results: Using a synthetic mix of viral particles, we made use of the T7 DNA polymerase (T7pol) to convert viral circular ssDNA molecules to dsDNA, while preventing over-replication of such molecules, as is the case with the Phi29 DNA polymerase. Our findings indicate that using T7pol and a mix of degenerated primers to convert ssDNA to dsDNA prior library preparation is a good alternative to the currently used methods. It better represents the original synthetic mixtures compared to MDA or direct application of the xGen kit. Furthermore, when applied to two complex virome samples, the T7pol treatment improved both the richness and abundance in the Microviridae fraction. Conclusion: We conclude that T7pol pretreatment is preferable to MDA for the shotgun sequencing of viromes, which is easy to implement and inexpensive.

genomics↗

bioRxiv2022

Comparison of interferometric light microscopy with nanoparticle tracking analysis for the study of extracellular vesicles and bacteriophages

Research on extracellular vesicles (EVs) and bacteriophages (phages) has been steadily expanding over the past decades as many of their roles in medicine, biology, and ecosystems have been unveiled. Such interest has brought about the need for new tools to quantify and determine the sizes of these biological nanoparticles. A new device based on interferometric light microscopy (ILM), the Videodrop, was recently developed for this purpose. Here, we compared this new device to two nanoparticle tracking analysis (NTA) devices, the NanoSight and the ZetaView, for the analysis of EVs and phages. We used EVs isolated from bacteria, fecal samples, bovine milk and human cells, and phages of various sizes and shape, ranging from 30 to 120 nm of diameter. While NTA instruments correctly enumerated most phages, the Videodrop detected only the largest one, indicating a lower sensitivity threshold compared to the NTA devices. Nevertheless, the performance of the Videodrop compared favorably to that of the NTA devices for the determination of the concentration of eukaryotic EV samples. The NanoSight instrument provided the most precise size distributions but the Videodrop was by far the most time-saving device, making it worthy of consideration for studies conducted on a large number of samples.

cell biology↗

bioRxiv2019

The spatial heterogeneity of the gut limits bacteriophage predation leading to the coexistence of antagonist populations of bacteria and their viruses

Bacteria and their viruses, bacteriophages (phages), are the most abundant components of the mammalian gut microbiota where these two entities coexist over time. The ecological dynamics underlying the coexistence between these two antagonistic populations in the gut are unknown. We challenged a murine synthetic bacterial community with a set of virulent phages, to study the factors allowing phages-bacteria coexistence in the gut. We found that coexistence was neither dependent on an arms race between bacteria and phages, nor on the ability of phages to extend host range. Instead, our data suggest that some phage-inaccessible sites in the mucosa of the ileum serve as a spatial refuge for bacteria, which from there disseminate in the gut lumen. Luminal phages amplify by infecting luminal bacteria maintaining phage throughout the gut. We conclude that the heterogeneous distribution of microbes in the gut contributes to the long-term coexistence of phages with phage-susceptible bacteria. This observation could explain the persistence in the human gut of intestinal phages, such as the crAssphage, as well as the low efficiency of oral phage therapy against enteric pathogens in animal models and clinical trials.

microbiology↗