High throughput study of biofilm and virulence in Listeria monocytogenes using innovative approaches

Bohyung Lee
Ecole Doctorale des Sciences de la Vie, Santé, Agronomie et Environnement (SVSAE) de l’Université Clermont Auvergne (UCA). Soutenue le 28 Mai 2019.

High throughput study of biofilm and virulence in Listeria monocytogenes using innovative approaches 

Listeria monocytogenes is a facultative anaerobic, Gram-positive and rod-shaped bacterium. It is multifaceted foodborne pathogen characterized by its adaptability in adverse conditions and proliferation in a wide range of environments from soil to mammalian host cells. The bacterium forms biofilms in food chain which is presumed to be a source of repeated food product contamination increasing the risk of listeriosis in consumers. L. monocytogenes isolates are grouped into four distinct phylogenetic divisions of 13 serotypes among which lineage I (mainly of 4b and 1/2b) and lineage II (mainly of 1/2a and 1/2c) represent most isolates. Their genomes are approximately 2.8-3.2 Mbp, composed of around 3,000 open reading frames with a high rate of nucleotide polymorphisms. The genetic heterogeneity is reflected on diversified clonal structure which correlates, to some extent, with phenotypic traits such as virulence or stress resistance. The thesis, therefore, investigated two most prominent phenotypes, biofilm formation and virulence potential, from various perspectives using state-of-the art technologies. Throughout the studies, large panels of isolates were used to represent the intraspecific diversity.

Firstly, sudden cold shock induced cellular adhesion to abiotic surfaces as a transient phenotypic change. In addition, cell surface of L. monocytogenes revealed strong electron-donor nature regardless of temperature and became more hydrophilic as cells adapted to cold. A mild but significant correlation was observed between affinity for ethyl acetate and cellular adhesion level suggesting the role of physicochemical property in adhesion step. Next, various food-related factors played distinct roles at different biofilm formation steps. Nutrient deprivation enhanced adhesion, however, impeded maturation step. Addition of NaCl to growth cultures stimulated biofilm production and, surprisingly, it significantly intensified biofilm maturation of nutrient-deprived cells. High degree of variation in relative biofilm productivity was observed among serotypes, genotypes, as well as isolates across culture conditions, however, certain genotype (clonal complex 26) revealed distinctively higher biofilm production under cold temperature (10°C) suggesting an association of genotype with biofilm phenotype. Assessment of genetic composition with regard to biofilm production by pan-genome-wide association study revealed that functions such as ‘Cell surface proteins’, ‘Soluble internalin, and ‘Transformation/Competence’ were highly enriched implying their roles in L. monocytogenes biofilm formation. Finally, transcriptome profiles were analysed in depth using RNA sequencing. Importantly, Principal Component Analysis refined a large dataset to strengthen experimental reproducibility and improve statistical power of correlation analyses. Certain transcriptional factors with key roles in virulence such as σB, PrfA, and CodY contributed to variations in basal transcripts level among isolates. High diversity of transcriptomes between lineage I and II as well as hyper- and hypovirulent genotypes was observed implying the importance of transcriptomic plasticity in the bacterial physiology. Transcripts level of numerous genes related to sugar metabolism and transport found to be correlated with in vivo virulence potential suggesting the involvement of such pathways in the infection in Galleria mellonella model system.

Conclusively, the thesis explored intraspecific diversity in L. monocytogenes and resulted in ample phenotypic, genomic, and transcriptomic findings. With the integrative omics approach in listeriology, the present work will contribute to unveiling the complex physiology and pathology of the bacterium.

Keywords: Listeria monocytogenes, biofilm, virulence, genomics, transcriptomics

Partager cet Article
Avez-vous aimé cet article ?
0 0
24 Comments
  1. Merci beaucoup pour la publication des résumés de thèse de Bohyung Lee et Tiago Santos. Je trouve cette nouvelle rubrique très informative et intéressante.
    Par contre, il est regrettable que le laboratoire et le(s) directeur(s) ou directrice(s) de thèse n’apparaissent nulle part dans la publication.
    Bien cordialement,

    Répondre
  2. buy generic propecia order fluconazole 100mg online purchase fluconazole online

    Répondre
  3. baycip online – buy ethambutol order augmentin 1000mg pills

    Répondre
  4. buy baycip pills – purchase cephalexin pill cheap clavulanate

    Répondre
  5. generic ciplox – chloromycetin tablet erythromycin 250mg drug

    Répondre
  6. brand metronidazole – generic terramycin 250mg zithromax 500mg over the counter

    Répondre
  7. valtrex 1000mg brand – order nemazole sale zovirax 800mg generic

    Répondre
  8. purchase ampicillin pill buy vibra-tabs without prescription purchase amoxil

    Répondre
  9. buy flagyl 200mg pills – cleocin 300mg usa buy azithromycin tablets

    Répondre
  10. buy furosemide online cheap – oral minipress buy captopril pills for sale

    Répondre
  11. glycomet 500mg tablet – epivir canada lincomycin order online

    Répondre
  12. order clozaril 50mg online – order aceon online cheap order pepcid 40mg online

    Répondre
  13. order zidovudine generic – epivir brand allopurinol 100mg pill

    Répondre
  14. generic anafranil 25mg – abilify 30mg tablet buy sinequan 25mg for sale

    Répondre
  15. seroquel 50mg for sale – generic seroquel 50mg eskalith online

    Répondre
  16. buy atarax – brand nortriptyline 25 mg amitriptyline ca

    Répondre
  17. buy augmentin 1000mg sale – order ciprofloxacin 500mg online cheap generic cipro 1000mg

    Répondre
  18. order amoxil online cheap – ceftin 500mg price buy cipro 1000mg generic

    Répondre
  19. buy zithromax 500mg pill – buy tinidazole 500mg for sale order ciplox 500 mg without prescription

    Répondre
  20. order cleocin 150mg online cheap – brand chloramphenicol order chloromycetin for sale

    Répondre
  21. price of stromectol – eryc cheap order cefaclor without prescription

    Répondre
  22. buy albuterol inhalator – seroflo cheap theo-24 Cr buy online

    Répondre
  23. medrol 4mg tablet – claritin online order order azelastine 10 ml sprayer

    Répondre
  24. clarinex oral – buy flixotide medication albuterol inhaler

    Répondre

Laisser une réponse

Votre adresse e-mail ne sera pas publiée. Les champs requis sont marqués *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>