Biology subjects

Ansaldi, M.

Publications and source records attributed to Ansaldi, M..

4 recordsLinked to original sources

bioRxiv2024

HieVi: Protein Large Language Model for proteome-based phage clustering

Viral taxonomy is a challenging task due to the propensity of viruses for recombination. Recent updates from the ICTV and advancements in proteome-based clustering tools highlight the need for a unified framework to organize bacteriophages (phages) across multiscale taxonomic ranks, extending beyond genome-based clustering. Meanwhile, self-supervised large language models, trained on amino acid sequences, have proven effective in capturing the structural, functional, and evolutionary properties of proteins. Building on these advancements, we introduce HieVi, which uses embeddings from a protein language model to define a vector representation of phages and generate a hierarchical tree of phages. Using the INPHARED dataset of 24,362 complete and annotated viral genomes, we show that in HieVi, a multi-scale taxonomic ranking emerges that aligns well with current ICTV taxonomy. We propose that this method, unique in its integration of protein language models for viral taxonomy, can encode phylogenetic relationships, at least up to the family level. It therefore offers a valuable tool for biologists to discover and define new phage families while unraveling novel evolutionary connections.

genomics↗

bioRxiv2024

Antibiotic-Induced Morphological Changes Enhance Phage Predation: A Mathematical Model of Plaque Formation in Structured Environments

A distinctive manifestation of phage infection in solid media is the appearance of lysis plaques, which correspond to the circular thinning of a bacterial lawn. During plaque formation, successive cycles of phage replication generally take place from a single point of infection and spread radially in a matrix of immobilized bacterial hosts. Many different factors affect plaque size, such as the composition and the reticulation of the propagation matrix, the characteristics of the phage, but also parameters related to the physiology of the bacterial host. Since combined administration of both antibiotics and phages is a common practice during compassionate treatments, our research focuses on the effects of antibiotics on phage predation, which can be of crucial importance for the therapeutic applications of phages. It has been previously observed that the presence of antibiotics at sublethal concentrations can affect drastically bacterial physiology, allowing phages to spread more rapidly and resulting in better bacterial eradication. Previous experimental work has focused on the phage characteristics that influence plaque size. However, as plaque formation is strongly influenced by host growth dynamics, a comprehensive model integrating both the host growth and phage infection parameters is required. In this work, we suggest that plaque enlargement is linked to morphological changes of the host that have an impact on the rate of epidemic propagation and certainly on phage diffusion into the matrix. To support this hypothesis, we characterized the growth parameters of two different phages and bacteria in semi-solid media in the presence of various antibiotics. By combining these data, we have produced a mathematical model that accounts for these observations and explains the increase in plaque size when the host morphology is affected. Significance StatementThis study provides new insights into the phenomenon of Phage-Antibiotic Synergy (PAS) by demonstrating that antibiotic-induced morphological changes in bacterial hosts play a critical role in enhancing phage propagation in structured environments. By linking these morphological alterations--such as cell filamentation and bloating--to increased lysis plaque size, the research underscores the importance of host dynamics in phage therapy. The development of a mathematical model integrating both host growth and phage infection parameters offers a novel framework for understanding and optimizing phage-based treatments in the presence of antibiotics, potentially improving therapeutic outcomes.

microbiology↗

bioRxiv2022

Phage-antibiotic synergy: cell filamentation is a key driver of successful phage predation

Phages are promising tools to fight antibiotic-resistant bacteria, and as for now, phage therapy is essentially performed in combination with antibiotics. Interestingly, combined treatments including phages and a wide range of antibiotics lead to an increased bacterial killing, a phenomenon called phage-antibiotic synergy (PAS), suggesting that antibiotic-induced changes in bacterial physiology alter the dynamics of phage propagation. Using single-phage and single-cell techniques, each step of the lytic cycle of phage HK620 was studied in E. coli cultures treated with either ciprofloxacin or cephalexin, two filamentation-inducing antibiotics. In the presence of sublethal doses of antibiotics, multiple stress tolerance and DNA repair pathways are triggered following activation of the SOS response. One of the most notable effects is the inhibition of bacterial division. As a result, a significant fraction of cells forms filaments that stop dividing but have higher rates of mutagenesis. Antibiotic-induced filaments become easy targets for phages due to their enlarged surface areas, as demonstrated by fluorescence microscopy and flow cytometry techniques. Adsorption, infection and lysis occur more often in filamentous cells compared to regular-sized bacteria. In addition, the reduction in bacterial numbers caused by impaired cell division may account for the faster elimination of bacteria during PAS. We developed a mathematical model to capture the interaction between sublethal doses of antibiotics and exposition to phages. This model shows that the induction of filamentation by sublethal doses of antibiotics can amplify the replication of phages and therefore yield PAS. We also use this model to study the consequences of PAS on the emergence of antibiotic resistance. A significant percentage of hyper-mutagenic filamentous bacteria are effectively killed by phages due to their increased susceptibility to infection. As a result, the addition of even a very low number of bacteriophages produced a strong reduction of the mutagenesis rate of the entire bacterial population. We confirm this prediction experimentally using reporters for bacterial DNA repair. Our work highlights the multiple benefits associated with the combination of sublethal doses of antibiotics with bacteriophages.

microbiology↗

bioRxiv2022

Genetic mining of newly isolated Salmophages for phage therapy

I.Salmonella enterica - a Gram negative zoonotic bacterium - is mainly a food-borne pathogen and the main cause of diarrhea in humans worldwide. Main reservoirs are found in poultry farms but also in wild birds. The development of antibiotic resistance in S. enterica species raises concerns about the future of efficient therapies against this pathogen and revives the interest in bacteriophages as a useful therapy against bacterial infections. Here we aimed at deciphering and functionally annotate 10 new Salmonella phage genomes isolated in Spain in the light of phage therapy. We designed a bioinformatic pipeline using available building blocks to de novo assemble genomes and perform syntaxic annotation. We then used genome-wide analyses for taxonomic annotation enabled by vContact2 and VICTOR. We were also particularly interested in improving functional annotation using remote homologies detection and comparisons with the recently published phage-specific PHROG protein database. We finally searched for useful functions for phage therapy such as systems encoded by the phage to circumvent cellular defenses with a particular focus on anti-CRIPSR proteins. We thus were able to genetically characterized nine virulent phages and one temperate phage and identified putative functions relevant to the formulation of phage cocktails for Salmonella biocontrol.

microbiology↗