Publications by authors named "Ludovic Mallet"

Article Synopsis
  • Typhimurium and its monophasic variant (4,[5],12:i:-) are common serovars, but their spread in French pig herds and slaughterhouses has not been previously explored at a regional level.
  • The study analyzed 188 strains from French pigs collected between 2014 and 2019, revealing limited genomic diversity, indicating that only a couple of clones are prevalent among pig populations.
  • By comparing these strains with international isolates, the research highlights specific genomic characteristics of the ST 34 monophasic variants in France, along with other findings related to virulence and antimicrobial resistance.
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Article Synopsis
  • Mycobacterium tuberculosis (Mtb) makes a special molecule called 1-tuberculosinyladenosine (1-TbAd) that helps it survive in human immune cells by blocking their functions.
  • Researchers found that certain genes are important for making 1-TbAd and used new software to study how Mtb produces lipids, leading to discoveries of many related molecules.
  • They also discovered that the genes for making 1-TbAd are present in some bacteria outside the usual group known for tuberculosis, showing how these genes could have spread and suggesting that these molecules might be important for understanding human TB disease.
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From a historically rare serotype, subsp. Dublin slowly became one of the most prevalent in cattle and raw milk cheese in some regions of France. We present a retrospective genomic analysis of 480 .

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Listeria monocytogenes (Lm) is a ubiquitous bacterium that causes listeriosis, a serious foodborne illness. In the nature-to-human transmission route, Lm can prosper in various ecological niches. Soil and decaying organic matter are its primary reservoirs.

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Although Salmonella Typhimurium (STM) and Salmonella Paratyphi A (SPA) belong to the same phylogenetic species, share large portions of their genome and express many common virulence factors, they differ vastly in their host specificity, the immune response they elicit, and the clinical manifestations they cause. In this work, we compared their intracellular transcriptomic architecture and cellular phenotypes during human epithelial cell infection. While transcription induction of many metal transport systems, purines, biotin, PhoPQ and SPI-2 regulons was similar in both intracellular SPA and STM, we identified 234 differentially expressed genes that showed distinct expression patterns in intracellular SPA vs.

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Bacillus thuringiensis (Bt) belongs to the Bacillus cereus (Bc) group, well known as an etiological agent of foodborne outbreaks (FBOs). Bt distinguishes itself from other Bc by its ability to synthesize insecticidal crystals. However, the search for these crystals is not routinely performed in food safety or clinical investigation, and the actual involvement of Bt in the occurrence of FBOs is not known.

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Plasmids are genetic elements that enable rapid adaptation and evolution by transferring genes conferring selective advantages to their hosts. Conjugative plasmids are predominantly responsible for the global dissemination of antimicrobial resistance, representing an important threat to global health. As the number of plasmid sequences grows exponentially, it becomes critical to depict the global diversity and decipher the distribution of circulating plasmids in the bacterial community.

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Background: Listeria monocytogenes Clonal Complexes (CCs) have been epidemiologically associated with foods, especially ready-to-eat (RTE) products for which the most likely source of contamination depends on the occurrence of persisting clones in food-processing environments (FPEs). As the ability of L. monocytogenes to adapt to environmental stressors met in the food chain challenges the efforts to its eradication from FPEs, the threat of persistent strains to the food industry and public health authorities continues to rise.

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The investigation of foodborne outbreaks (FBOs) from genomic data typically relies on inspecting the relatedness of samples through a phylogenomic tree computed on either SNPs, genes, kmers, or alleles (i.e., cgMLST and wgMLST).

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Article Synopsis
  • Eusocial termites evolved from cockroaches around 150 million years ago, earlier than bees and ants, with their genomes showing significant differences from these Hymenoptera.
  • Scientists analyzed the genomes of the German cockroach and the drywood termite to uncover genes related to pheromone communication and caste determination, which are vital for their social structures.
  • The findings reveal that while termites and Hymenoptera share some evolutionary mechanisms for eusociality, they have developed unique solutions, illustrating an example of convergence in complex biological evolution.
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The unique ability of the tuberculosis (TB) bacillus, Mycobacterium tuberculosis, to persist for long periods of time in lung hypoxic lesions chiefly contributes to the global burden of latent TB. We and others previously reported that the M. tuberculosis ancestor underwent massive episodes of horizontal gene transfer (HGT), mostly from environmental species.

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Background: Small regulatory RNAs (sRNAs) are widely found in bacteria and play key roles in many important physiological and adaptation processes. Studying their evolution and screening for events of coevolution with other genomic features is a powerful way to better understand their origin and assess a common functional or adaptive relationship between them. However, evolution and coevolution of sRNAs with coding genes have been sparsely investigated in bacterial pathogens.

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Motivation: Genome sequencing projects sometimes uncover more organisms than expected, especially for complex and/or non-model organisms. It is therefore useful to develop software to identify mix of organisms from genome sequence assemblies.

Results: Here we present PhylOligo, a new package including tools to explore, identify and extract organism-specific sequences in a genome assembly using the analysis of their DNA compositional characteristics.

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While it has long been thought that all genomic novelties are derived from the existing material, many genes lacking homology to known genes were found in recent genome projects. Some of these novel genes were proposed to have evolved de novo, ie, out of noncoding sequences, whereas some have been shown to follow a duplication and divergence process. Their discovery called for an extension of the historical hypotheses about gene origination.

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Among the most common forms of interaction between species are those between hosts and their parasites and they have important implications for evolutionary theory. Understanding both the phenotypic and genotypic processes governing such interactions is a major endeavour in biology, but is a complex and challenging task. The development of next generation sequencing technologies has recently opened up this field from a molecular perspective, allowing us access to the genomic data underlying laboratory or wild phenotypes.

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Deciphering the genetic bases of pathogen adaptation to its host is a key question in ecology and evolution. To understand how the fungus Magnaporthe oryzae adapts to different plants, we sequenced eight M. oryzae isolates differing in host specificity (rice, foxtail millet, wheat, and goosegrass), and one Magnaporthe grisea isolate specific of crabgrass.

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Motivation: This website allows the detection of horizontal transfers based on a combination of parametric methods and proposes an origin by researching neighbors in a bank of genomic signatures. This bank is also used to research an origin to DNA fragments from metagenomics studies.

Results: Different services are provided like the possibility of inferring a phylogenetic tree with sequence signatures or comparing two genomes and displaying the rearrangements that happened since their separation.

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Background And Aims: Among cardiovascular risk factor, people with Down syndrome have a lower plasma homocysteine level. In a previous study, we have shown that DYRK1A (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1a), a serine/threonine kinase found on human chromosome 21, is implicated on homocysteine metabolism regulation. Indeed, mice that overexpress in liver this kinase have a lower plasma homocysteine level concomitant with an increased hepatic S-adenosyhomocysteine hydrolase (SAHH) activity, which depends on the activation of NAD(P)H:quinone oxidoreductase-1 (NQO1).

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Background: Numerous cases of horizontal transfers (HTs) have been described for eukaryote genomes, but in contrast to prokaryote genomes, no whole genome evaluation of HTs has been carried out. This is mainly due to a lack of parametric methods specially designed to take the intrinsic heterogeneity of eukaryote genomes into account. We applied a simple and tested method based on local variations of genomic signatures to analyze the genome of the pathogenic fungus Aspergillus fumigatus.

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