Biology subjects

Schwabe, M.

Publications and source records attributed to Schwabe, M..

4 recordsLinked to original sources

bioRxiv2026

Heterogeneous flux capacity and oxygen sensitivity lead to subcellular ETC flux gradients in mouse oocytes

Mitochondria are metabolic hubs of the cell that provide energy and metabolites to meet the energetic, biosynthetic and signaling demands of the cell. Mitochondrial activities are characterized by the metabolic fluxes through their internal metabolic pathways. One of the most important mitochondrial metabolic pathways is the electron transport chain (ETC), where electron carriers such as NADH donate their electrons to oxygen to power mitochondrial respiration. Mitochondrial activities are dynamically and spatially regulated during organism development to ensure robust development. Recent work has revealed the existence of a subcellular ETC flux gradient within a single mouse oocyte, where mitochondria closer to the cell membrane display a higher ETC flux, but the mechanism underlying the formation of this gradient is unknown. In this work, we study the origin of the ETC flux gradients by modulating them through perturbations of external oxygen concentration and temperature. Interpreting the data with spatial kinetic modeling of mitochondrial respiration, we discover that the subcellular ETC flux gradient cannot be explained by reaction-diffusion of oxygen alone, but is a result of mitochondrial heterogeneity where mitochondria closer to the cell membrane display larger ETC flux capacity and lower oxygen sensitivity. Our work suggests that kinetically distinct subpopulations of mitochondria are spatially sorted according to their metabolic activities to form intracellular metabolic gradients.

biophysics↗

bioRxiv2024

In-host evolution of classic to convergent Klebsiella pneumoniae sequence type 147 isolates and impact of associated capsular changes on different morphotypes

Klebsiella pneumoniae, an important opportunistic pathogen, has long been categorized into two distinct pathotypes: the often multidrug-resistant classic (cKp) and the highly virulent hypervirulent (hvKp). However, a recent global trend has witnessed the emergence of convergent strains, seamlessly combining antimicrobial resistance with hypervirulence. Our study delved into a series of K. pneumoniae isolates sourced from the same patient, all belonging to the international, high-risk clonal lineage of sequence type 147. As reported in a previous study, these isolates exhibited diverse morphotypes on blood agar, ranging from small white to normal-sized white, grey, or grey and dry (g/d) colonies. Through an interplay of omics and phenotypic experiments, we unraveled the intricate mechanisms governing these distinct colony morphologies and their implications on bacterial virulence and resilience. While the earlier isolates demonstrated modest levels of resistance and virulence, their later counterparts showed significantly heightened levels, attributed to the acquisition of additional plasmids. Bioinformatics analysis unveiled a chromosomal insertion of a hybrid plasmid in one isolate, marking an unprecedented in-host microevolution from the classic to the convergent pathotype. All morphotypes exhibited positive insertion sequences around or within the K loci, with the grey or g/d phenotypes arising from impaired K loci. Despite lower serum resistance, these morphotypes demonstrated superior adhesion to human epithelial cells. Interestingly, while capsule-deficient strains are conventionally associated with decreased virulence, our isolates displayed high mortality rates in the Galleria mellonella infection model. In conclusion, our findings not only provide unprecedented insights into in-host microevolution within a patient, transitioning from the classic to the convergent pathotype, but also contribute significantly to the understanding of the diverse morphotypes exhibited by K. pneumoniae.

microbiology↗

bioRxiv2024

Temperatures above 37°C increase virulence of a convergent Klebsiella pneumoniae sequence type 307 strain

Hypermucoviscosity in Klebsiella pneumoniae is often related to the overexpression of capsular polysaccharides, regulated by complex biosynthetic mechanisms in response to external cues. However, little is known about the processes involved in hypermucoviscosity in convergent K. pneumoniae, which combine extensive drug resistance with high bacterial virulence, under pathophysiological conditions. This study aimed to fill this gap by investigating the temperature dependence of hypermucoviscosity and overall virulence in a convergent K. pneumoniae strain isolated during a clonal outbreak belonging to the high-risk sequence type (ST)307. Hypermucoviscosity, biofilm formation, and mortality rates in Galleria mellonella larvae were examined at different temperatures (room temperature, 28{degrees}C, 37{degrees}C, 40{degrees}C and 42{degrees}C) and with various phenotypic experiments including electron microscopy. The underlying mechanisms of the phenotypic changes were explored via qPCR analysis to evaluate plasmid copy numbers, and transcriptomics. Our results indicate a temperature-dependent "switch" above 37{degrees}C to a hypermucoviscous phenotype, correlating with increased biofilm formation capacity and in vivo mortality, which might be due to a bacterial response to pathophysiological conditions, i.e., fever. In addition, we detected upregulation of a hybrid plasmid encoding both carbapenemase and the mucoid regulator rmpA genes. Surprisingly, rmpA did not exhibit temperature-dependent differential gene expression, suggesting other drivers. Apparent co-regulation of hypermucoviscosity and fimbrial expression was also identified. This study not only revealed the impact that increased temperatures above 37{degrees}C have on hypermucoviscosity and virulence in a convergent K. pneumoniae strain but contributes to the understanding of previously unrecognized dimension of K. pneumoniaes behavior, emphasizing its adaptability to changing environments. Abstract importanceUnderstanding the temperature-dependent dynamics of hypermucoviscosity in Klebsiella pneumoniae is crucial for unraveling the intricacies of its hypervirulence. This study investigates a convergent K. pneumoniae strain, ST307, revealing a temperature-dependent switch to hypermucoviscosity above 37 {degrees}C. The findings showcase a correlation between increased temperature, hypermucoviscosity, enhanced attachment, and heightened in vivo mortality. Notably, a hybrid plasmid encoding carbapenemase and mucoid regulator genes was upregulated at elevated temperatures. The study sheds light on previously unexplored aspects of K. pneumoniae behavior, emphasizing its adaptability in response to changing environments. The identified temperature-associated regulatory mechanisms offer insights into the pathogens response to fever, contributing to our broader understanding of bacterial adaptation. This research contributes to addressing the global challenge of hypervirulent, drug-resistant K. pneumoniae strains, providing valuable implications for future treatment strategies.

microbiology↗

bioRxiv2023

Multi-omics investigations uncover unique pathogenic markers in clinical Klebsiella pneumoniae that could be leveraged as novel antimicrobial targets

BackgroundKlebsiella pneumoniae (KP), often multidrug-resistant (MDR), is a significant public health concern and frequently associated with various diseases including urinary-tract infection. In addition, in recent years, an increasing number of studies reports on the emergence of convergent KP that combine MDR with hypervirulence leading to severely limited treatment options and thus calling for alternative approaches. MethodsIn this study, we compared high-risk clonal KP lineages with less pathogenic Klebsiella variicola (KV) and Klebsiella quasipneumoniae (KQ) strains on multiple-omics levels and performed integrative data analysis to identify unique markers that could be subsequently leveraged as novel targets in alternative treatment strategies. ResultsOur initial genomic analysis revealed 107 genes as part of the patho-core genome in eight clinical KP that were associated with different metabolic pathways. Subsequent transcriptome and proteome analyses in infection-mimicking media demonstrated similar regulatory patterns among KP vs. other Klebsiella strains, again with metabolic responses playing a pivotal role. In total, we identified 193 KP-specific, differentially expressed genes on transcriptomic and/or proteomic levels. When then comparing these regulated genes to over 6,000 publicly available Klebsiella genomes, we identified unique markers either in KP genomes or adaptively regulated on transcriptomics and/or proteomics levels. An example for the latter was a gene cluster for the cellobiose phosphotransferase system that has been previously described in the context of bacterial virulence and biofilm formation. ConclusionIn conclusion, our study not only highlights that KP strains demonstrate metabolic flexibility in response to particular environmental conditions, which is potentially important for their success as opportunistic pathogens, but identified unique KP-markers. Subsequent studies are needed to explore whether these markers might be prospectively used as novel anti-virulence targets, providing alternatives to traditional antibiotics.

microbiology↗