Mycobacterium marinum antagonistically induces an autophagic response while repressing the autophagic flux in a TORC1- and ESX-1-dependent manner.

Autophagy is a eukaryotic catabolic process also participating in cell-autonomous defence. Infected host cells generate double-membrane autophagosomes that mature in autolysosomes to engulf, kill and digest cytoplasmic pathogens. However, several bacteria subvert autophagy and benefit from its machinery and functions. Monitoring infection stages by genetics, pharmacology and microscopy, we demonstrate that the ESX-1 secretion system of Mycobacterium marinum, a close relative to M. tuberculosis, upregulates the transcription of autophagy genes, and stimulates autophagosome formation and recruitment to the mycobacteria-containing vacuole (MCV) in the host model organism Dictyostelium. Antagonistically, ESX-1 is also essential to block the autophagic flux and deplete the MCV of proteolytic activity. Activators of the TORC1 complex localize to the MCV in an ESX-1-dependent manner, suggesting an important role in the manipulation of autophagy by mycobacteria. Our findings suggest that the infection by M. marinum activates an autophagic response that is simultaneously repressed and exploited by the bacterium to support its survival inside the MCV

Supplemental movies

These movies are supplemental material used for the article submitted as a preprint here : https://www.biorxiv.org/content/10.1101/2022.12.19.521111v1THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Test dataset for BBQ methods

The provided dataset contains images of fixed infected RAW264.7 cells infected with Mycobacterium tuberculosis and imaged by fluorescence confocal microscopy. These images are provided to test the proposed Bacterial Burden Quantification (BBQ) workflows that can be found on GitHub here : https://github.com/jaugenst/BBQTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Molecular and cellular biochemistry

Warnericin RK from Staphylococcus warneri and PSMalpha from Staphylococcus epidermidis are anti-Legionella peptides which were differently classified in a previous study according to their mode of action. Indeed, warnericin RK is highly hemolytic with a bactericidal mode of action, whereas PSMalpha is poorly hemolytic with a bacteriostatic mode of action toward L. pneumophila. In order to find anti-Legionella peptides which are not hemolytic, a collection of peptides varying in sequence from warnericin RK to PSMalpha were designed and synthesized, and their anti-Legionella activities, in terms of growth inhibition, permeabilization, and bactericidal effect, as well as their hemolytic activities, were measured and compared. The results showed that some residues, at position 14 for both peptides for instance, were of major importance for bactericidal and hemolytic activities