Biology subjects

Stubbusch, A. K. M.

Publications and source records attributed to Stubbusch, A. K. M..

4 recordsLinked to original sources

bioRxiv2026

Dominance of metabolically flexible fermenters drives intestinal gas production in Crohn's disease

Molecular hydrogen (H2) and hydrogen sulfide (H2S) are central gut metabolites that shape microbial metabolism and affect host health. In Crohns disease (CD), the shift in microbiota composition ( dysbiosis) is associated with intestinal accumulation of these gases, but the responsible microbes remain poorly resolved. Here, we analysed 4,644 bacterial and archaeal species-level genomes from the Unified Human Gastrointestinal Genome Collection to identify H2-cycling microbes, assessed their prevalence in ca. 1,700 stool metagenomes from healthy and diseased individuals, and validated their activity using culture-based incubations of stool isolates and biopsy samples. Approximately half of all species encoded H2-producing abilities, with acetate- and propionate-forming fermenters such as Phocaeicola and Bacteroides dominating healthy cohorts, whereas comparatively few taxa, including Escherichia and Megamonas, encoded H2 consuming abilities. In CD, H2 producers became more abundant but less diverse, favouring species with multiple H2-evolving hydrogenases and more fermentation routes, especially Clostridium and Enterocloster species. Consistently, isolates enriched in CD produced H2 faster and at higher concentrations than health-associated isolates. Increased H2S-producing capacity in CD was driven mainly by these H2-producing fermenters carrying anaerobic sulfite reductases (Asr), rather than sulfate-reducing bacteria, and was supported by elevated H2S production in Asr-positive isolates, likely providing an additional electron sink. These findings provide a species-resolved view of gut gas metabolism and implicate metabolically flexible fermenters in excessive gas and sulfide production in gut disorders.

microbiology↗

bioRxiv2024

Antagonism as a foraging strategy in microbial communities

In natural habitats, nutrient availability limits bacterial growth. We discovered that bacteria can overcome this limitation by acquiring nutrients through lysing neighboring cells via contact-dependent antagonism. Using single-cell live imaging and isotopic markers, we found that during starvation the type VI secretion system, which transfers toxins into neighboring cells, increases growth by enabling the uptake of nutrients from lysing cells. In a spatially structured environment, the gradual lysis of just a few target cells allows for the growth of a new antagonist cell. Genomic adaptations in antagonists, characterized by a reduced metabolic gene repertoire, and the prevalence of the type VI secretion system in natural environments, such as global oceans and soils, suggest that bacterial antagonism has the potential to substantially contribute to nutrient transfer within microbial communities across various ecosystems.

microbiology↗

bioRxiv2023

Polysaccharide breakdown products drive degradation-dispersal cycles of foraging bacteria through changes in metabolism and motility

Most of Earths biomass is composed of polysaccharides. During biomass decomposition, polysaccharides are degraded by heterotrophic bacteria as a nutrient and energy source and are thereby partly remineralized into CO2. As polysaccharides are heterogeneously distributed in nature, following the colonization and degradation of a polysaccharide hotspot the cells need to reach new polysaccharide hotspots. Even though many studies indicate that these degradation-dispersal cycles contribute to the carbon flow in marine systems, we know little about how cells alternate between polysaccharide degradation and motility, and which environmental factors trigger this behavioral switch. Here, we studied the growth of the marine bacterium Vibrio cyclitrophicus ZF270 on the abundant marine polysaccharide alginate, both in its soluble polymeric form as well as on its breakdown products. We used microfluidics coupled to time-lapse microscopy to analyze motility and growth of individual cells, and RNA sequencing to study associated changes in gene expression. We found that single cells grow at reduced rate on alginate until they form large groups that cooperatively break down the polymer. Exposing cell groups to digested alginate accelerates cell growth and changes the expression of genes involved in alginate degradation and catabolism, central metabolism, ribosomal biosynthesis, and transport. However, exposure to digested alginate also triggers cells to become motile and disperse from cell groups, proportionally increasing with the group size before the nutrient switch, and this is accompanied by high expression of genes involved in flagellar assembly, chemotaxis, and quorum sensing. The motile cells chemotax toward polymeric but not digested alginate, likely enabling them to find new polysaccharide hotspots. Overall, our findings reveal cellular mechanisms that might also underlie bacterial degradation-dispersal cycles, which influence the remineralization of biomass in marine environments. ImportancePolysaccharides, also known as glycans, are the most abundant form of biomass on Earth and understanding how they are degraded by microorganisms is essential for our understanding of the global carbon cycle and the storage and release of CO2 by natural systems. Although group formation is a common strategy used by bacterial cells to degrade ubiquitous polymeric growth substrates in nature, where nutrient hotspots are heterogeneously distributed, little is known about how cells prepare for dispersal from an exhausted nutrient source and re-initiate degradation of new nutrient patches. By quantifying growth, motility and chemotaxis of individual cells and comparing gene expression changes when populations were exposed to either polysaccharides or their degradation products in the form of digested polysaccharides, we show that bacterial cells alter their behavior when they experience a shift from polymeric to digested polysaccharides: After cells form groups during growth on polymers, the exposure to degradation products triggered cells to become motile, enabling dispersal from sessile cell groups. The chemotactic attraction of motile cells to polymeric alginate likely allows cells to move towards new polysaccharide hotspots. Our study sheds light on the cellular processes that drive bacterial growth and behavior during carbon remineralization, an important process resulting in CO2 release from natural systems.

microbiology↗

bioRxiv2022

Extracellular appendages govern spatial dynamics and growth of Caulobacter crescentus on a prevalent biopolymer

Microbial breakdown of carbon polymers is an essential process in all ecosystems. Carbon polymers generally require extracellular breakdown by secreted exoenzymes. Exoenzymes and breakdown products can be lost through diffusion or flow. This diffusional loss is reduced when bacteria grow in surface-associated populations where they benefit from each others metabolic activities. The aquatic organism Caulobacter crescentus was recently shown to form clonal microcolonies on the carbon polymer xylan, but to grow solitary on the monosaccharide xylose. The underlying mechanisms of this substrate-mediated microcolony formation are unknown. In particular, the importance of extracellular appendages such as pili, adhesive holdfast, and flagellum in governing the spatial arrangement of surface-grown cells is unclear. Using microfluidics coupled to automated time-lapse microscopy and quantitative image analysis, we compared the temporal and spatial dynamics of C. crescentus wildtype and mutant strains grown on xylan, xylose, or glucose. We found that mutants lacking type IV pili or holdfast showed altered spatial patterns in microcolonies and were unable to maintain cell densities above a threshold required for maximal growth rates on the xylan polymer, whereas mutants lacking flagella showed increased cell densities that potentially lead to increased local competition. Our results demonstrate that extracellular appendages allow bacteria to reach local cell densities that maximize single-cell growth rates in response to their nutrient environment.

microbiology↗