IMM events :
The Institut de Microbiologie de la Méditerranée (IMM) organises scientific seminars for researchers every Friday at 11.30am.
These seminars are announced in the Institute’s diary.
The seminar organising committee is made up of :
– Bénédicte BURLAT, researcher at BIP
– Isabelle IMBERT, teacher-researcher at LISM
– Vladimir PELICIC, researcher at the LCB
– Hugo BISIO, researcher at IGS
Seminar information :
– Frequency: Every Friday
– Time: 11.30 a.m.
– Accessibility: These events are not open to the general public. For open events, please consult the public events page.
List of Seminars:
Below is the list of scientific seminars scheduled for the coming month.
If you have any questions or require further information, please do not hesitate to contact the organising committee: seminaires@imm.cnrs.fr
Exploring the integration of competence and transformation into the lifestyle of the human
pathogen Streptococcus pneumoniae
Calum Johnston (Laboratoire de Microbiologie et Génétique Moléculaires, UMR5100, Centre de Biologie Intégrative, Toulouse)
Exploring the integration of competence and transformation into the lifestyle of the human
pathogen Streptococcus pneumoniae
Natural genetic transformation is a mechanism of horizontal gene transfer well conserved in the bacterial kingdom. It involves the active capture and uptake of exogenous DNA in the form of single strands, followed by integration into the recipient chromosome by homologous recombination. This mechanism allows bacteria to acquire new genetic traits and can facilitate the spread of antibiotic resistance.
In the human pathogen Streptococcus pneumoniae (the pneumococcus), transformation occurs during a transient physiological state called competence, which can be induced by stresses such as antibiotics. The pneumococcal competence regulon is comprised of ~100 genes, with only 20 required for transformation, suggesting that competence plays other roles in pneumococcal biology.
In this talk, I will present recent studies on pneumococcal transformation1 and competence2,3. Firstly, I will discuss how early homologous recombination intermediates of transformation interact with active replication forks to access the recipient chromosome. This defines a key mechanistic step in the transformation process. Secondly, I will show how a novel cell communication mechanism controlling populational competence drives phenotypic heterogeneity within a population, providing it with novel properties such as increased antibiotic tolerance. This reveals competence as a general stress response in the pneumococcus, of which transformation is just one facet. Taken together, these studies demonstrate how competence and transformation are key mechanisms integrated into the lifestyle of the pneumococcus.
References:
1 – Johnston CHG, Hope R, Soulet AL, Dewailly M, De Lemos D, Polard P. The RecA-directed recombination pathway of natural transformation initiates at chromosomal replication forks in Streptococcus pneumoniae. PNAS. 2023 Feb 21;120(8).
2 – Johnston CHG, Prudhomme M, Soulet AL, Boyeldieu A, De Lemos D, Campo N, Polard P. Pneumococcal competence is a populational health sensor driving multilevel heterogeneity in response to antibiotics. Nat Commun. 2024 Ju 10;15(1):5625.
3 – De Lemos D, Soulet AL, Morales V, Bergé MJ, Polard P, Johnston CHG. Competence induction of homologous recombination genes protects pneumococcal cells from genotoxic stress. mBio 2025 Jan, 8;16(1)
Invited by Emilia Mauriello (LCB)