Padilla-Gomez, J. | Search bioRxiv

bioRxiv2025

Systems analysis reveals alternate metabolic states adopted by Mycobacterium tuberculosis across species

Mycobacterium tuberculosis (Mtb) persists within macrophages, yet how different host species shape bacterial state remains poorly understood. Here, we directly compared the intracellular transcriptome of Mtb during infection of human and mouse macrophages, revealing distinct host-imposed microenvironments that drive the pathogen into separable metabolic states. Lipid metabolism and regulatory circuits were prominently remodeled, with mouse macrophages inducing iron- and oxidative-stress responses while human macrophages promoted fatty acid import programs. Using fluorescent fatty acid tracing, we uncovered a striking species-specific phenotype: Mtb forms intracellular lipid inclusions (ILIs) in murine macrophages but not in human macrophages. This phenotype was independent of culture media, macrophage ontogeny, or host antimicrobial factors such as nitric oxide and itaconate. Access of Mtb to host-derived lipids required the ESX-1 secretion system and was inversely correlated with host triacylglycerol (TAG) synthesis. Inhibition of TAG formation in human macrophages partially restored Mtb ILI formation, revealing a metabolic gate that governs lipid flow between host lipid droplets and intracellular Mtb. Together, these findings establish a cross-species framework for decoding host-driven bacterial metabolic states and identify a key barrier limiting Mtbs access to host lipid stores in human macrophages.

microbiology↗

bioRxiv2024

Genes required for the formation of virulence-provoking bacterial sphingolipids

Sphingolipids are ubiquitous in membranes of eukaryotes and are associated with important cellular functions. Although sphingolipids occur scarcely in bacteria, for some of them they are essential and, in other bacteria, they contribute to fitness and stability of the outer membrane, such as in the well-studied -proteobacterium Caulobacter crescentus. We previously defined five structural genes for ceramide synthesis in C. crescentus. However, other mutants affected in genes of this same genomic region show cofitness with a mutant deficient in serine palmitoyltransferase. Here we show that at least two phospho-sphingolipids are produced in C. crescentus and that at least another six gene products are needed for the decoration of ceramide upon phospho-sphingolipid formation. All eleven genes participating in phospho-sphingolipid formation are also required in C. crescentus for membrane stability and for displaying sensitivity towards the antibiotic polymyxin B. The genes for the formation of complex phospho-sphingolipids are also required for C. crescentus virulence on Galleria mellonella insect larvae. Author SummarySphingolipids participate in the formation of biological membranes and molecular signaling in higher organisms. Many bacteria also accommodate sphingolipids in their membranes. Here we report that eleven genes participate in the synthesis of complex bacterial phospho-sphingolipids. Our data show that these lipids contribute to membrane stability, but also confer sensitivity towards certain antibiotics. The bacterium Caulobacter crescentus is widely distributed in fresh water lakes and streams and was considered to be non-virulent. However, we demonstrate that complex phospho-sphingolipids are the main virulence contributors in this bacterium.

microbiology↗