Borrero-de Acuna, J. M. | bioRxiv Science

bioRxiv2024

Bacterial membrane vesicles of Pseudomonas aeruginosa activate AMPK signaling through inhibition of mitochondrial complex III

Bacterial membrane vesicles (BMVs) are secreted by many pathogenic bacteria and known to stimulate various host responses upon infection, thereby contributing to the pathogenicity of bacterial pathogens like Pseudomonas aeruginosa. While the effects of BMVs on host immune responses are well studied, little is known about their impact on cell metabolism and mitochondrial respiration. Here, we show that P. aeruginosa BMVs (1) reprogram cell metabolism of human lung cells, (2) negatively affect mitochondrial respiration by (3) specifically inhibiting complex III of the electron transport chain leading to (4) the activation of AMP-activated protein kinase (AMPK) signaling which in turn results in (5) AMPK-dependent inhibition of global protein synthesis.

cell biology↗

bioRxiv2023

Isolation and quantification of bacterial membrane vesicles for quantitative metabolic studies using mammalian cell cultures

Bacterial membrane vesicles (BMVs) are produced by most bacteria and participate in various cellular processes, such as intercellular communication, nutrient exchange, and pathogenesis. Notably, these vesicles can contain virulence factors, including toxic proteins, DNA, and RNA. Such factors can contribute to the harmful effects of bacterial pathogens on host cells and tissues. Although the general effects of BMVs on host cellular physiology are well known, the underlying molecular mechanisms are less understood. In this study, we introduce a vesicle quantification method, leveraging the membrane dye FM4-64. We utilize a linear regression model to analyze the fluorescence emitted by stained vesicle membranes to ensure consistent and reproducible vesicle-host interaction studies using cultured cells. This method is particularly valuable for identifying host cellular processes impacted by vesicles and their specific cargo. Moreover, it outcompetes clearly unreliable protein concentration-based methods. We (1) show a linear correlation between the quantity of vesicles and the fluorescence signal emitted from the FM4-64 dye, (2) introduce the "vesicle load" as a new semi-quantitative unit, facilitating more reproducible vesicle-cell culture interaction experiments (3) show that a stable vesicle load yields consistent host responses when studying vesicles from Pseudomonas aeruginosa mutants (4) demonstrate that typical vesicle isolation contaminants, such as flagella, do not significantly skew the metabolic response of lung epithelial cells to P. aeruginosa vesicles, and (5) identify inositol-1-monophosphatase (SuhB) as a pivotal regulator in the vesicle-mediated pathogenesis of P. aeruginosa.

cell biology↗

bioRxiv2020

Work horse strain Clostridioides difficile 630Δerm is oblivious to its anaerobic lifestyle

The laboratory reference strain 630{Delta}erm of the anaerobic human pathogen Clostridioides difficile is characterized by a remarkable high oxygen tolerance. We show that an amino acid exchange in the DNA binding domain of the hydrogen peroxide sensor PerR results in a constitutive derepression of PerR-controlled genes and thus in an oxidative stress response even under anaerobic conditions. This questions the model status, strain 630{Delta}erm claims in C. difficile research.

microbiology↗