Biology subjects

Koliwer-Brandl, H.

Publications and source records attributed to Koliwer-Brandl, H..

4 recordsLinked to original sources

bioRxiv2026

PDIM drives the transition from repairable to catastrophic EsxA-mediated vacuole membrane damage during Mycobacterium marinum infection

During infection, pathogenic mycobacteria damage the membrane of the Mycobacterium-containing vacuole (MCV), triggering host repair responses that preserve an intracellular permissive niche before bacteria escape to the cytosol at later stages. How the MCV transitions from repairable injury to catastrophic rupture remains poorly understood. Here, we dissected the respective contributions of the ESX-1 effectors EsxA/EsxB and the cell-envelope lipid phthiocerol dimycocerosate (PDIM) during Mycobacterium marinum infection of the amoeba Dictyostelium discoideum. Combining host reporters for membrane damage and repair with single and double bacterial mutants, we show that EsxA/EsxB and PDIM are both required for full intracellular virulence but act at distinct stages of MCV damage progression. Loss of EsxA/EsxB strongly reduced recruitment of ESCRT and autophagy reporters to the MCV, demonstrating that EsxA initiates repairable membrane lesions. In contrast, PDIM-deficient bacteria retained the ability to recruit early damage reporters and ESCRT machinery but showed reduced autophagy-associated repair, failed to efficiently acquire cytosolic perilipin coating, and remained largely confined within the MCV. Genetic disruption of host autophagy restored cytosolic access and intracellular growth of PDIM-deficient bacteria, indicating that PDIM is specifically required to overcome host repair capacity rather than to initiate damage. Importantly, the sequential requirement for EsxA and PDIM was conserved during infection of murine microglial BV-2 cells. Remarkably, PDIM-defective mutants induced lysenin recruitment, a reporter of sphingomyelin exposure, but progression to autophagy engagement was strongly decreased. Together, our results support a two-step model in which EsxA initiates MCV membrane damage, while PDIM amplifies these lesions towards catastrophic rupture, enabling escape to the cytosol and dissemination.

microbiology↗

bioRxiv2026

Intracellular compartmentalization shapes lipid access and metabolic fitness of mycobacteria

Intracellular mycobacteria encounter distinct metabolic environments as they transition between vacuolar and cytosolic compartments within host cells, yet how nutrient access is shaped by this compartmentalization remains poorly understood. Here, we use Mycobacterium marinum fatty acyl- CoA ligase 6 (FACL6) as a functional entry point to examine how lipid acquisition and processing are coordinated during intracellular infection. By combining host and bacterial genetic perturbations with dual RNA-sequencing and high-resolution imaging in genetically tractable amoebal infection models, and validating key phenotypes in mammalian cells, we show that lipid metabolic programs in intracellular mycobacteria are tightly linked to subcellular localization. Sterol utilization and neutral lipid storage are preferentially engaged during the intravacuolar phase, whereas cytosolic exposure is associated with reduced lipid accumulation. Deletion of facl6 disrupts this coordinated scenario, resulting in altered bacterial cell envelope architecture, premature membrane damage, defective neutral lipid storage, and reduced intracellular fitness despite enhanced cytosolic access. Together, these findings reveal that loss of FACL6 causes intrinsic defects in lipid handling and highlight how compartment-specific lipid environments shape the outcome of mycobacterial infection. TeaserLoss of FACL6 reveals how intracellular compartmentalization shapes mycobacterial lipid metabolism

cell biology↗

bioRxiv2022

Engineered reporter phages for rapid detection of Escherichia coli, Klebsiella spp., and Enterococcus spp. in urine

The rapid detection and species-level differentiation of bacterial pathogens facilitates antibiotic stewardship and improves disease management. Here, we develop a rapid bacteriophage-based diagnostic assay to detect the most prevalent pathogens causing urinary tract infections: Escherichia coli, Klebsiella spp., and Enterococcus spp. For each uropathogen, two virulent phages were genetically engineered to express a nanoluciferase reporter gene upon host infection. Using 206 patient urine samples, reporter phage-induced bioluminescence was quantified to identify bacteriuria and the assay was benchmarked against conventional urinalysis. Overall, E. coli, Klebsiella spp., and Enterococcus spp. were each detected with high sensitivity (68%, 78%, 85%), specificity (99%, 99%, 99%), and accuracy (90%, 94%, 96%) at a resolution of [>=]103 CFU/ml within 5 h. We further demonstrate how bioluminescence in urine can be used to predict phage antibacterial activity, demonstrating the future potential of reporter phages as companion diagnostics that guide patient-phage matching prior to therapeutic phage application.

microbiology↗

bioRxiv2019

Zinc intoxication of Mycobacterium marinum during Dictyostelium discoideum infection is counteracted by induction of the pathogen Zn2+ exporter CtpC

Macrophages use diverse strategies to kill or restrict intracellular pathogens. Some of these strategies involve the deprivation of bacteria from (micro)nutrients such as transition metals, and the bacteria intoxication through metal accumulation. Little is known about the chemical warfare between Mycobacterium marinum, a close relative of the human pathogen M. tuberculosis, and its hosts. Here we use the professional phagocyte Dictyostelium discoideum to investigate the role of Zn2+ during M. marinum infection. We show that M. marinum infection induces the accumulation of Zn2+ inside the Mycobacterium-containing vacuole (MCV), achieved by the induction and recruitment of the D. discoideum Zn2+ efflux pumps ZntA and ZntB. In cells lacking the ZntA detoxifying transporter there is further attenuation of M. marinum growth, possibly due to a compensatory efflux of Zn2+ into the MCV. This efflux is presumably carried out by ZntB, the main Zn2+ transporter in endosomes and phagosomes. Counterintuitively, M. marinum growth is also impaired in zntB KO cells, where MCVs accumulate less Zn2+. We also demonstrate that M. marinum senses toxic levels of Zn2+ and responds by upregulating its Zn2+ exporter CtpC, which supports bacteria survival under these restrictive conditions. Attenuation of M. marinum intracellular proliferation in zntA and zntB KO cells is accentuated in the absence of CtpC, confirming that mycobacteria face noxious levels of Zn2+. Altogether, we show for the first time that M. marinum infection induces a deleterious Zn2+ elevation in D. discoideum, which is counteracted by the bacteria with the induction of its Zn2+ exporter CtpC.

cell biology↗