Flavia BOLLARO PhD defense
Obtention and characterization of antimicrobial agents from lichen-associated bacteria for biotechnological applications
Organic Chemistry & Interfaces (COrInt) team
Abstract
The exploration of microbial resources associated with lichens represents a promising strategy for the discovery of new bioactive metabolites. In this study, a collection of bacterial strains derived from the lichen Rhizocarpon geographicum was investigated for its antimicrobial potential against plant pathogens (Erwinia amylovora, Venturia inaequalis) and human pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli).
Among the tested strains, six bacterial culture supernatants exhibited significant antimicrobial activities, associated with promising biosynthetic potential highlighted by genomic analyses. Two strains, Pseudarthrobacter phenanthrenivorans 171 and Pseudomonas antarctica 141, were selected for further study using an OSMAC approach coupled with large-scale fermenter cultures.
P. phenanthrenivorans 171 exhibited marked antimicrobial activity, correlated with the production of desferrioxamine E, suggesting a direct link between siderophore production and the observed antimicrobial activity.
P. antarctica 141 exhibited strong biosynthetic potential and reproducible antibacterial activity, influenced by culture conditions. Metabolomic analyses revealed the presence of siderophores such as pyochelin, but the activity appears to result from a combination of several metabolites rather than a single compound.
These results highlight the importance of metabolic interactions and environmental factors in modulating bioactivity. This study demonstrates that microbial communities associated with lichens represent a valuable and underutilized source of bioactive metabolites, offering promising prospects for the development of new antimicrobial agents for applications in cosmetics and agronomy.
Jury
Angèle Lengo Mambu, Professor, University of Limoges / Reviewer
Marion Girardot, Associate Professor, University of Poitiers / Reviewer
Céline Rivière, Professor, University of Lille / Examiner
Ahmed Taïbi, Project Manager, Greencell / Invited
Sylvain Tranchimand, Associate Professor, University of Rennes, ENSCR, ISCR / PhD Co-Supervisor
Sophie Tomasi, Professor, University of Rennes, ISCR / PhD Director
Assia Dreux-Zigha, Directrice R&D Greencell / PhD Co-Director
Contacts
Flavia Bollaro, flavia.bollaro@univ-rennes.fr
Sophie Tomasi, sophie.tomasi@univ-rennes.fr
Sylvain Tranchimand, sylvain.tranchimand@ensc-rennes.fr
