Host-Microbe Interactome

Lipid Dynamics during Mycobacterial Infections

Tuberculosis (Tb) is caused by Mycobacterium tuberculosis and remains one of the deadliest infectious diseases. The World Health Organization (WHO) estimates that in 2021, Tb killed 1.6 million people emphasizing the importance to develop new drugs, vaccines and diagnostic tools to reduce this burden in the future.

M. tuberculosis employs multiple strategies to survive intracellularly. One of its most striking adaptations is its ability to utilize host lipids such as fatty acids and sterols to: (i) generate energy, (ii) build its characteristic lipid-rich cell wall and (iii) produce storage lipids during infection. To be constantly in a fatty acid-rich environment, the pathogen actively contributes to generate the “foamy” phenotype in host macrophages, for which the accumulation of host lipid droplets (LDs) is characteristic.

Balancing Act: How a perturbation in fatty acid homeostasis impacts on vacuolar escape of mycobacteria

To import fatty acids from their environment, mycobacteria are equipped with sophisticated transport machineries. However, the mechanism by which fatty acids are esterified with coenzyme A (“fatty acid activation”), an essential step for their further turnover, remains elusive. ​This project aims to characterize the function of fatty acid-activating enzymes in lipid synthesis and vacuolar escape of mycobacteria using the D. discoideum/M. marinum system.

​​To characterize fatty acid flows and metabolism in host and bacteria mutants depleted in fatty acid-activating enzymes, a protocol that combines the use of bifunctional FA probes with expansion microscopy and lipidomics is established. - This project is part of the SPP2225.

Functional impact of lipid logistics during mycobacterial infection

This project aims to identify lipid metabolic pathways that are hijacked by intracellular mycobacteria to exploit lipids from the host. To monitor alterations in lipid levels, we are establishing mass spectrometry lipidomics and thin layer chromatography for the D. discoideum/M. marinum system. In the future, we will determine the consequences of blocking specific lipid supply routes on various stages of the mycobacterial infection course. Collectively, these efforts may uncover novel therapeutic targets to fight mycobacteria infection.

Induction of membrane contact sites during mycobacterial infection

Various intracellular pathogens, including M. tuberculosis, damage the membrane of their vacuoles to impair fundamental innate immune functions and to trigger their translocation into the host cytosol. The host counteracts membrane damage by recruiting membrane repair machineries to retain the pathogen inside the vacuole. ​

Using advanced imaging approaches, our group investigates the role of ER-dependent membrane repair and other repair machineries during mycobacteria infection. For example, to investigate the formation of membrane contact sites between the ER and the MCV, we employ advanced imaging techniques. Specifically, we utilize several 3D-CLEM approaches that include high-pressure freezing and TEM-tomography (as described in Franzkoch and Anand et al., 2023, BioRxiv) as well as serial block-face SEM (Anand et al., 2023, BioRxiv). This, together with spinning disc live cell imaging and flow cytometry, uncovered that ER-dependent repair constitutes a host defense mechanism against intracellular pathogens such as M. tuberculosis (Anand et al., 2023, BioRxiv).  - This project is part of the SFB1557 @Uni Osnabrück.