Abstract
Mycobacterium tuberculosis, the agent of human tuberculosis has developed different virulence mechanisms and virulence-associated tools during its evolution to survive and multiply inside the host. Based on previous reports and by analogy with other bacteria, phospholipases C (PLC) of M. tuberculosis were thought to be among these tools. To get deeper insights into the function of PLCs, we investigated their putative involvement in the intracellular lifestyle of M. tuberculosis, with emphasis on phagosomal rupture and virulence, thereby re-visiting a research theme of longstanding interest. Through the construction and use of an M. tuberculosis H37Rv PLC-null mutant (ΔPLC) and control strains, we found that PLCs of M. tuberculosis were not required for induction of phagosomal rupture and only showed marginal, if any, impact on virulence of M. tuberculosis in the cellular and mouse infection models used in this study. In contrast, we found that PLC-encoding genes were strongly upregulated under phosphate starvation and that PLC-proficient M. tuberculosis strains survived better than ΔPLC mutants under conditions where phosphatidylcholine served as sole phosphate source, opening new perspectives for studies on the role of PLCs in the lifecycle of M. tuberculosis.
Highlights
Mycobacterium abscessus, which represents an exceptional, emerging pathogen within the large group of otherwise mostly harmless fast-growing mycobacteria[9,10,11,12], encodes a PLC involved in the intracellular survival of M. abscessus in amoebae[13]
M. tuberculosis was reported to produce membrane-damaging proteins associated with the ESX-1 secretion system, which are required for induction of phagosomal rupture and bacterial access to the cytosolic compartment of infected phagocytic cells[4], it remains unknown if other bacterial factors, as for example PLCs, might contribute to the M. tuberculosis-mediated disruption of the phagosomal membrane
Tuberculosis strains harbour four PLC encoding genes. These genes, named plcA, plcB, plcC and plcD are located at two different genomic loci in M. tuberculosis, with plcA-B-C organised as an operon at genome coordinates 2632–2627 kb of strain H37Rv, and plcD, represented as a single gene, located about 640 kb upstream of plcA-C25
Summary
Mycobacterium abscessus, which represents an exceptional, emerging pathogen within the large group of otherwise mostly harmless fast-growing mycobacteria[9,10,11,12], encodes a PLC involved in the intracellular survival of M. abscessus in amoebae[13]. The first main objective of our study was to investigate whether the biological activities of ESX-1 and mycobacterial PLCs were linked For this purpose, we constructed a PLC-deletion mutant in the M. tuberculosis H37Rv genetic background, and subjected it to dedicated cell-biological analyses in comparison with the wild-type (WT) M. tuberculosis H37Rv strain. Results from the phagosomal rupture assay together with virulence tests in cellular and small animal infection models allowed us to revisit the role of PLCs of M. tuberculosis in the infection process, which to our surprise was found to be only marginal. These results open new perspectives for future research to elucidate the biological role of PLCs in M. tuberculosis and related slow-growing mycobacteria
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
