Biology subjects

Scorza, K.

Publications and source records attributed to Scorza, K..

3 recordsLinked to original sources

bioRxiv2026

Bacterial vitamin sharing emerges from a balance between release and uptake

Vitamin availability often shapes microbial communities, as many microbes use vitamins they cannot synthesize. Yet how vitamins become available to users remains poorly understood. To explore this process, we quantified vitamin B12 synthesis, uptake, and extracellular accumulation across hundreds of diverse soil, freshwater, and marine bacterial isolates. These measurements revealed distinct source-sink phenotypes and showed that producers vary substantially in the amount of B12 they provide extracellularly. B12 synthesis was predictable across divergent bacterial lineages from genome content, whereas uptake and extracellular accumulation were not. Controlled cell-death experiments and independently parameterized models showed that extracellular B12 could be quantitatively predicted from release by dead cells and reuptake by surviving cells. Thus, extracellular B12 availability is governed not by synthesis alone, but by the balance between release and uptake, with producer reuptake acting as a previously overlooked sink.

microbiology↗

bioRxiv2024

Gut Bacteria Metabolize Natural and Synthetic Steroid Hormones via the Reductive OsrABC Pathway

Steroid hormone metabolism by the gut microbiome affects host physiology, but the underlying microbial pathways remain incompletely understood. Here, we isolate a novel human gut bacterium, Clostridium steroidoreducensT strain HCS.1 that reduces cortisol and related steroid hormones to 3{beta},5{beta}-tetrahydrosteroid products. Through transcriptomics and enzymatic discovery, we establish the C. steroidoreducens OsrABC steroid hormone pathway. OsrA is a 3-oxo-{Delta}1-steroid hormone reductase that targets synthetic glucocorticoids, including prednisolone-- a frontline Crohns disease therapy. OsrB is a 3-oxo-{Delta}4-steroid reductase that converts steroid hormones to 5{beta}-dihydrosteroid intermediates, which OsrC subsequently reduces to 3{beta},5{beta}-tetrahydro products. Homologs of osrA and osrB predict steroid-reducing activity across gut bacteria and are enriched in Crohns disease patient metagenomes. Consistent with a role in modulating drug efficacy, C. steroidoreducens colonization decreases prednisolone bioavailability in gnotobiotic mice. These findings thus define a previously unrecognized pathway for microbial steroid hormone inactivation and establish a mechanistic basis for bacterial interference with anti-inflammatory therapies.

microbiology↗

bioRxiv2022

Exceptionally versatile respiratory metabolisms drive metabolite production by diverse gut bacteria

Respiratory reductases enable microbes to utilize molecules present in anaerobic ecosystems as energy-generating respiratory electron acceptors. Here we identify three taxonomically distinct families of human gut bacteria (Burkholderiaceae, Eggerthellaceae, Erysipelotrichaceae) that encode large arsenals of tens-to-hundreds of respiratory-like reductases per genome. Screening species from each family (Sutterella wadsworthensis, Eggerthella lenta, and Holdemania filiformis), we discover 22 metabolites used as respiratory electron acceptors in a species-specific manner. Identified reactions transform multiple classes of dietary- and host-derived metabolites, including bioactive molecules resveratrol and itaconate. Products of identified respiratory metabolisms highlight poorly characterized compounds, such as the itaconate-derived 2-methylsuccinate. Reductase substrate-profiling defines enzyme-substrate pairs and reveals a complex picture of reductase evolution, providing evidence that reductases with specificities for related cinnamate substrates independently emerged at least four times. These studies thus establish an exceptionally versatile form of anaerobic respiration that directly links microbial energy metabolism to the gut metabolome.

microbiology↗