Search

Your search keyword '"Héchard, Yann"' showing total 263 results
Start Over Author "Héchard, Yann"
263 results on '"Héchard, Yann"'

11. Characterization of Rosculus vilicus sp. nov., a rhizarian amoeba interacting with Mycobacterium avium subsp. paratuberculosis.

Author

Jessu, Amélie, Delafont, Vincent, Moyen, Jean-Louis, Biet, Franck, Samba-Louaka, Ascel, and Héchard, Yann

Abstract

Free-living amoebae are described as potential reservoirs for pathogenic bacteria in the environment. It has been hypothesized that this might be the case for Mycobacterium avium subsp. paratuberculosis, the bacterium responsible for paratuberculosis. In a previous work, we isolated an amoeba from a water sample in the environment of infected cattle and showed that this amoeba was associated with Mycobacterium avium subsp. paratuberculosis. While a partial 18S rRNA gene has allowed us to suggest that this amoeba was Rosculus-like, at that time we were not able to subcultivate it. In the present study, we succeeded in cultivating this strain at 20–25°C. This amoeba is among the smallest (5–7  μm) described. The sequencing of the whole genome allowed us to extract the full 18S rRNA gene and propose this strain as a new species of the Rosculus genus, i.e., R. vilicus. Of note, the mitochondrial genome is particularly large (184,954  bp). Finally, we showed that this amoeba was able to phagocyte Mycobacterium avium subsp. paratuberculosis and that the bacterium was still observed within amoebae after at least 3  days. In conclusion, we characterized a new environmental amoeba species at the cellular and genome level that was able to interact with Mycobacterium avium subsp. paratuberculosis. As a result, R. vilicus is a potential candidate as environmental reservoir for Mycobacterium avium subsp. paratuberculosis but further experiments are needed to test this hypothesis. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

27. Here, there and everywhere: Ecology and biology of the Dependentiae phylum.

Author

Weisse, Louis, Héchard, Yann, Moumen, Bouziane, and Delafont, Vincent

Subjects
*DNA data banks, *BIOLOGY, *DARK matter, *DNA sequencing, *BACTERIAL diversity, *METAGENOMICS
Abstract

Our view of bacterial diversity has been dramatically impacted by cultivation‐independent approaches such as metagenomics and 16S rRNA gene sequencing. Consequently, most bacterial phyla known to date are only documented by the presence of DNA sequences in databases and lack cultivated representatives. This bacterial majority that is yet‐to‐be cultivated, is forming the 'Microbial Dark Matter', (MDM) a consortium, whose ecology and biology remain largely unexplored. The Candidatus Dependentiae stands as one of many phyla within this MDM, found worldwide in various environments. Genomic evidence suggests ancestral, unusual adaptations of all Ca. Dependentiae to a host dependent lifestyle. In line with this, protists appear to be important for Ca. Dependentiae biology, as revealed by few recent studies, which enabled their growth in laboratory through host cultivation. However, the Ca. Dependentiae still remain to this day a poorly documented phylum. The present review aims to summarize the current knowledge accumulated on this often found, but rarely highlighted, bacterial phylum. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

37. Legionella pneumophilasubverts the antioxidant defenses of its amoeba host Acanthamoeba castellanii

Author

Hay, Alban, Aucher, Willy, Pigeault, Romain, Bertaux, Joanne, Crépin, Alexandre, Remaury, Quentin Blancart, Héchard, Yann, Samba-Louaka, Ascel, and Villéger, Romain

Abstract

•Legionella pneumophilainduced an upregulation of antioxidant defense transcripts in Acanthamoeba castellaniiat 6 h post-infection (p.i.), resulting in decreased ROS quantity at 24 h p.i..•We identified 97 intracellular metabolites disrupted during the infection of A. castellaniiby L. pneumophilain a TSS4-dependent manner.•Four metabolites in A. castellaniiexhibited a reduced abundance following infection by L. pneumophila, potentially contributing to the maintenance of an antioxidant state in the host.•Pre-exposure of amoebae to pro-oxidizing molecules may facilitate bacterial multiplication at 24 h p.i..

Published
2025
Full Text
View/download PDF

46. Encystment Induces Down-Regulation of an Acetyltransferase-Like Gene in Acanthamoeba castellanii

Author

Rolland, Steven, Mengue, Luce, Noël, Cyril, Crapart, Stéphanie, Mercier, Anne, Aucher, Willy, Héchard, Yann, Samba-louaka, Ascel, Rolland, Steven, Mengue, Luce, Noël, Cyril, Crapart, Stéphanie, Mercier, Anne, Aucher, Willy, Héchard, Yann, and Samba-louaka, Ascel

Abstract

Acanthamoeba castellanii is a ubiquitous free-living amoeba. Pathogenic strains are causative agents of Acanthamoeba keratitis and granulomatous amoebic encephalitis. In response to adverse conditions, A. castellanii differentiate into cysts, which are metabolically inactive and resistant cells. This process, also named encystment, involves biochemical and genetic modifications that remain largely unknown. This study characterizes the role of the ACA1_384820 Acanthamoeba gene during encystment. This gene encodes a putative N-acetyltransferase, belonging to the Gcn5-related N-acetyltransferase (GNAT) family. We showed that expression of the ACA1_384820 gene was down-regulated as early as two hours after induction of encystment in A. castellanii. Interestingly, overexpression of the ACA1_384820 gene affects formation of cysts. Unexpectedly, the search of homologs of ACA1_384820 in the Eukaryota gene datasets failed, except for some species in the Acanthamoeba genus. Bioinformatics analysis suggested a possible lateral acquisition of this gene from prokaryotic cells. This study enabled us to describe a new Acanthamoeba gene that is down-regulated during encystment.

Published
2020
Full Text
View/download PDF

47. Resistance of the oyster pathogen Vibrio tasmaniensis LGP32 against grazing by Vannella sp . marine amoeba involves Vsm and CopA virulence factors

Author

Robino, Etienne, Poirier, Aurore C., Amraoui, Hajar, Le Bissonnais, Sandra, Perret, Angelique, Lopez‐joven, Carmen, Auguet, Jean-christophe, Rubio, Tristan P., Cazevieille, Chantal, Rolland, Jean-luc, Héchard, Yann, Destoumieux‐garzón, Delphine, Charrière, Guillaume, Robino, Etienne, Poirier, Aurore C., Amraoui, Hajar, Le Bissonnais, Sandra, Perret, Angelique, Lopez‐joven, Carmen, Auguet, Jean-christophe, Rubio, Tristan P., Cazevieille, Chantal, Rolland, Jean-luc, Héchard, Yann, Destoumieux‐garzón, Delphine, and Charrière, Guillaume

Abstract

ibrios are ubiquitous in marine environments and opportunistically colonize a broad range of hosts. Strains of Vibrio tasmaniensis present in oyster farms can thrive in oysters during juvenile mortality events and behave as facultative intracellular pathogen of oyster hemocytes. Herein, we wondered whether V. tasmaniensis LGP32 resistance to phagocytosis is specific to oyster immune cells or contributes to resistance to other phagocytes, like marine amoebae. To address this question, we developed an integrative study, from the first description of amoeba diversity in oyster‐farms to the characterization of LGP32 interactions with amoebae. An isolate of the Vannella genus, Vannella sp. AP1411, which was collected from oyster farms, is ubiquitous, and belongs to one clade of Vannella that could be found associated with Vibrionaceae. LGP32 was shown to be resistant to grazing by Vannella sp. AP1411 and this phenotype depends on some previously identified virulence factors: secreted metalloprotease Vsm and copper efflux p‐ATPase CopA, which act at different steps during amoeba‐vibrio interactions, whereas some other virulence factors were not involved. Altogether, our work indicate that some virulence factors can by involved in multi‐host interactions of V. tasmaniensis ranging from protozoans to metazoans, potentially favoring their opportunistic behavior.

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results