Bile acid oxidation by<i>Eggerthella lenta</i>strains C592 and DSM 2243<sup>T</sup>
Bibliographic record
Abstract
Strains of Eggerthella lenta are capable of oxidation-reduction reactions capable of oxidizing and epimerizing bile acid hydroxyl groups. Several genes encoding these enzymes, known as hydroxysteroid dehydrogenases (HSDH) have yet to be identified. It is also uncertain whether the products of E. lenta bile acid metabolism are further metabolized by other members of the gut microbiota. We characterized a novel human fecal isolate identified as E. lenta strain C592. The complete genome of E. lenta strain C592 was sequenced and comparative genomics with the type strain (DSM 2243) revealed high conservation, but some notable differences. E. lenta strain C592 falls into group III, possessing 3α, 3β, 7α, and 12α-hydroxysteroid dehydrogenase (HSDH) activity, as determined by mass spectrometry of thin layer chromatography (TLC) separated metabolites of primary and secondary bile acids. Incubation of E. lenta oxo-bile acid and iso-bile acid metabolites with whole-cells of the high-activity bile acid 7α-dehydroxylating bacterium, Clostridium scindens VPI 12708, resulted in minimal conversion of oxo-derivatives to lithocholic acid (LCA). Further, Iso-chenodeoxycholic acid (iso-CDCA; 3β,7α-dihydroxy-5β-cholan-24-oic acid) was not metabolized by C. scindens. We then located a gene encoding a novel 12α-HSDH in E. lenta DSM 2243, also encoded by strain C592, and the recombinant purified enzyme was characterized and substrate-specificity determined. Genomic analysis revealed genes encoding an Rnf complex (rnfABCDEG), an energy conserving hydrogenase (echABCDEF) complex, as well as what appears to be a complete Wood-Ljungdahl pathway. Our prediction that by changing the gas atmosphere from nitrogen to hydrogen, bile acid oxidation would be inhibited, was confirmed. These results suggest that E. lenta is an important bile acid metabolizing gut microbe and that the gas atmosphere may be an important and overlooked regulator of bile acid metabolism in the gut.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".