Biology subjects

Kloehn, J.

Publications and source records attributed to Kloehn, J..

4 recordsLinked to original sources

bioRxiv2026

Early metabolic reprogramming licenses Streptococcus pneumoniae for Influenza-driven superinfection

Bacterial pneumonia remains a major cause of morbidity and mortality following influenza A virus (IAV) infection. However, the adaptive mechanisms that enable pathogen expansion in the post-viral lung remain poorly defined. Here, using a mouse model of IAV-Streptococcus pneumoniae superinfection, we characterize bacterial transcriptional reprogramming in vivo. We identify alcohol dehydrogenases (AdhA and AdhE), that support NAD regeneration during mixed-acid fermentation, as key determinants of bacterial fitness specifically in the IAV-primed lung. Genetic deletion of these results in a pronounced fitness defect during superinfection but not in primary bacterial pneumonia. Consistent with this requirement, pharmacological inhibition of alcohol dehydrogenases limits bacterial expansion and dissemination following IAV infection. Mechanistically, we show that IAV infection profoundly remodels the lung environment, inducing hypoxia and increasing the availability of alternative carbon sources, which together impose a metabolic dependency on Adh for bacterial expansion. Our findings place metabolic adaptation as a central driver of pneumococcal outgrowth following viral infection and reveal exploitable vulnerabilities for therapeutic intervention.

microbiology↗

bioRxiv2025

Redefining the role of the Plasmodium heme detoxification protein: From hemozoin formation to mitochondrial protein synthesis

Throughout their intraerythrocytic development, malaria parasites digest up to 80% of the host cells hemoglobin within a specialized degradative compartment known as the digestive vacuole. This process releases heme, which is detoxified by sequestration into bioinert hemozoin crystals. Although heme biomineralization is essential for blood-stage survival and a validated drug target, its underlying mechanisms remain unclear. Initially identified as a potent inducer of {beta}-hematin crystallization in vitro, the parasites Heme Detoxification Protein (HDP) has been proposed to execute a similar role in the formation of hemozoin crystals in cellulo. Here, we investigate the function of HDP in live Plasmodium falciparum parasites, integrating experimental genetic approaches with quantitative microscopy, cellular bioenergetics and whole-proteome profiling. Endogenous tagging revealed that HDP localizes to the mitochondrion rather than the digestive vacuole. Conditional inactivation of HDP resulted in a gradual loss of mitochondrial membrane potential, preceding developmental arrest. Bypassing the essential role of the respiratory chain in pyrimidine biosynthesis - either through exogenous electron acceptors or expression of a ubiquinone-independent dihydroorotate dehydrogenase - rescued HDP-deficient parasites, indicating a role in maintaining respiratory chain activity. Consistent with this, electron flow through complex IV was abolished in rescued HDP-null parasites, rendering them hypersensitive to proguanil, an antimalarial that synergizes with respiratory chain inhibitors. We found that loss of HDP leads to a marked reduction of complexes III and IV, whose integrity depends on mitochondrial protein biosynthesis. Integration of quantitative proteomic data with structure-guided homology modelling supports a role for HDP as part of the large mitoribosomal subunit at the inter-subunit contact site. By contrast, HDP loss did not affect the quantity of hemozoin or other heme species, crystal morphology, or sensitivity to the hemozoin-targeting drug chloroquine. Together, these findings challenge previous models linking HDP to hemozoin formation and instead reveal an essential role for HDP in mitochondrial protein biosynthesis.

microbiology↗

bioRxiv2024

N -acetylglucosamine supplementation fails to bypass the critical acetylation of glucosamine-6-phosphate required for Toxoplasma gondii replication and invasion

The cell surface of Toxoplasma gondii is rich in glycoconjugates which hold diverse and vital functions in the lytic cycle of this obligate intracellular parasite. Additionally, the cyst wall of bradyzoites, that shields the persistent form responsible for chronic infection from the immune system, is heavily glycosylated. Formation of glycoconjugates relies on activated sugar nucleotides, such as uridine diphosphate N-acetylglucosamine (UDP- GlcNAc). The Glucosamine-phosphate-N-acetyltransferase (GNA1) generates N- acetylglucosamine-6-phosphate critical to produce UDP-GlcNAc. Here, we demonstrate that downregulation of T. gondii GNA1 results in a severe reduction of UDP-GlcNAc and a concomitant drop in glycosylphosphatidylinositol (GPI), leading to impairment of the parasites ability to invade and replicate in the host cell. Surprisingly, attempts to rescue this defect through exogenous GlcNAc supplementation fail to completely restore these essential functions. In depth metabolomic analyses elucidate diverse causes underlying the failed rescue: utilization of GlcNAc is inefficient under glucose-replete conditions and fails to restore UDP-GlcNAc levels in GNA1-depleted parasites. In contrast, GlcNAc- supplementation under glucose-deplete conditions fully restores UDP-GlcNAc levels but fails to rescue the defects associated with GNA1 depletion. Our results underscore the essentiality of GlcN6P acetylation in governing T. gondii replication and invasion and highlight the potential of the evolutionary divergent GNA1 in Apicomplexa as a target for the development of much-needed new therapeutic strategies.

microbiology↗

bioRxiv2021

Pantothenate biosynthesis is critical for chronic infection by the neurotropic parasite Toxoplasma gondii

Coenzyme A (CoA) is an essential molecule acting in metabolism, post-translational modification, and regulation of gene expression. While all organisms synthesize CoA, many, including humans, are unable to produce its precursor, pantothenate. Intriguingly, like most plants, fungi and bacteria, parasites of the coccidian subgroup of Apicomplexa, including the human and animal pathogen Toxoplasma gondii, possess all the enzymes required for de novo synthesis of pantothenate. Here, the importance of CoA and pantothenate biosynthesis for the acute and chronic stages of T. gondii infection was dissected through genetic, biochemical and metabolomic approaches, revealing that CoA synthesis is essential for T. gondii tachyzoites, due to the parasites inability to salvage CoA or intermediates of the pathway. In contrast, de novo pantothenate synthesis was only partially active in T. gondii tachyzoites, making the parasite reliant on Pan uptake. However, Pan synthesis proved to be crucial for the establishment of chronic infection, offering a promising target for intervention against the persistent stage of T. gondii.

microbiology↗