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Mohanty I, Allaband C, Mannochio-Russo H, El Abiead Y, Hagey LR, Knight R, Dorrestein PC. The changing metabolic landscape of bile acids - keys to metabolism and immune regulation. Nat Rev Gastroenterol Hepatol 2024; 21:493-516. [PMID: 38575682 DOI: 10.1038/s41575-024-00914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/14/2024] [Indexed: 04/06/2024]
Abstract
Bile acids regulate nutrient absorption and mitochondrial function, they establish and maintain gut microbial community composition and mediate inflammation, and they serve as signalling molecules that regulate appetite and energy homeostasis. The observation that there are hundreds of bile acids, especially many amidated bile acids, necessitates a revision of many of the classical descriptions of bile acids and bile acid enzyme functions. For example, bile salt hydrolases also have transferase activity. There are now hundreds of known modifications to bile acids and thousands of bile acid-associated genes, especially when including the microbiome, distributed throughout the human body (for example, there are >2,400 bile salt hydrolases alone). The fact that so much of our genetic and small-molecule repertoire, in both amount and diversity, is dedicated to bile acid function highlights the centrality of bile acids as key regulators of metabolism and immune homeostasis, which is, in large part, communicated via the gut microbiome.
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Affiliation(s)
- Ipsita Mohanty
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Celeste Allaband
- Department of Pediatrics, University of California San Diego School of Medicine, La Jolla, CA, USA
| | - Helena Mannochio-Russo
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Yasin El Abiead
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Lee R Hagey
- Department of Medicine, University of California San Diego, San Diego, CA, USA
| | - Rob Knight
- Department of Pediatrics, University of California San Diego School of Medicine, La Jolla, CA, USA
- Center for Microbiome Innovation, University of California San Diego, La Jolla, CA, USA
- Department of Computer Science and Engineering, University of California San Diego, La Jolla, CA, USA
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Pieter C Dorrestein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
- Center for Microbiome Innovation, University of California San Diego, La Jolla, CA, USA.
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA.
- Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
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Comparative Analysis of Bile-Salt Degradation in Sphingobium sp. Strain Chol11 and Pseudomonas stutzeri Strain Chol1 Reveals Functional Diversity of Proteobacterial Steroid Degradation Enzymes and Suggests a Novel Pathway for Side Chain Degradation. Appl Environ Microbiol 2021; 87:e0145321. [PMID: 34469190 DOI: 10.1128/aem.01453-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The reaction sequence for aerobic degradation of bile salts by environmental bacteria resembles degradation of other steroid compounds. Recent findings show that bacteria belonging to the Sphingomonadaceae use a pathway variant for bile-salt degradation. This study addresses this so-called Δ4,6-variant by comparative analysis of unknown degradation steps in Sphingobium sp. strain Chol11 with known reactions found in Pseudomonas stutzeri Chol1. Investigations of strain Chol11 revealed an essential function of the acyl-CoA dehydrogenase (ACAD) Scd4AB for growth with bile salts. Growth of the scd4AB deletion mutant was restored with a metabolite containing a double bond within the side chain which was produced by the Δ22-ACAD Scd1AB from P. stutzeri Chol1. Expression of scd1AB in the scd4AB deletion mutant fully restored growth with bile salts, while expression of scd4AB only enabled constricted growth in P. stutzeri Chol1 scd1A or scd1B deletion mutants. Strain Chol11 Δscd4A accumulated hydroxylated steroid metabolites which were degraded and activated with coenzyme A by the wild type. Activities of five Rieske type monooxygenases of strain Chol11 were screened by heterologous expression and compared to the B-ring cleaving KshABChol1 from P. stutzeri Chol1. Three of the Chol11 enzymes catalyzed B-ring cleavage of only Δ4,6-steroids, while KshABChol1 was more versatile. Expression of a fourth KshA homolog, Nov2c228, led to production of metabolites with hydroxylations at an unknown position. These results indicate functional diversity of proteobacterial enzymes for bile-salt degradation and suggest a novel side chain degradation pathway involving an essential ACAD reaction and a steroid hydroxylation step. IMPORTANCE This study highlights the biochemical diversity of bacterial degradation of steroid compounds in different aspects. First, it further elucidates an unexplored variant in the degradation of bile-salt side chains by sphingomonads, a group of environmental bacteria that is well-known for their broad metabolic capabilities. Moreover, it adds a so far unknown hydroxylation of steroids to the reactions Rieske monooxygenases can catalyze with steroids. Additionally, it analyzes a proteobacterial ketosteroid-9α-hydroxylase and shows that this enzyme is able to catalyze side reactions with nonnative substrates.
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Feller FM, Holert J, Yücel O, Philipp B. Degradation of Bile Acids by Soil and Water Bacteria. Microorganisms 2021; 9:1759. [PMID: 34442838 PMCID: PMC8399759 DOI: 10.3390/microorganisms9081759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/22/2021] [Accepted: 08/12/2021] [Indexed: 02/07/2023] Open
Abstract
Bile acids are surface-active steroid compounds with a C5 carboxylic side chain at the steroid nucleus. They are produced by vertebrates, mainly functioning as emulsifiers for lipophilic nutrients, as signaling compounds, and as an antimicrobial barrier in the duodenum. Upon excretion into soil and water, bile acids serve as carbon- and energy-rich growth substrates for diverse heterotrophic bacteria. Metabolic pathways for the degradation of bile acids are predominantly studied in individual strains of the genera Pseudomonas, Comamonas, Sphingobium, Azoarcus, and Rhodococcus. Bile acid degradation is initiated by oxidative reactions of the steroid skeleton at ring A and degradation of the carboxylic side chain before the steroid nucleus is broken down into central metabolic intermediates for biomass and energy production. This review summarizes the current biochemical and genetic knowledge on aerobic and anaerobic degradation of bile acids by soil and water bacteria. In addition, ecological and applied aspects are addressed, including resistance mechanisms against the toxic effects of bile acids.
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Affiliation(s)
- Franziska Maria Feller
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Johannes Holert
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Onur Yücel
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
| | - Bodo Philipp
- Institute for Molecular Microbiology and Biotechnology, University of Münster, Corrensstr. 3, 48149 Münster, Germany; (F.M.F.); (J.H.); (O.Y.)
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Auf dem Aberg 1, 57392 Schmallenberg, Germany
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Proteome, bioinformatic and functional analyses reveal a distinct and conserved metabolic pathway for bile salt degradation in the Sphingomonadaceae. Appl Environ Microbiol 2021; 87:e0098721. [PMID: 34260303 DOI: 10.1128/aem.00987-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bile salts are amphiphilic steroids chain with digestive functions in vertebrates. Upon excretion, bile salts are degraded by environmental bacteria. Degradation of the bile-salt steroid skeleton resembles the well-studied pathway for other steroids like testosterone, while specific differences occur during side-chain degradation and the initiating transformations of the steroid skeleton. Of the latter, two variants via either Δ1,4- or Δ4,6-3-ketostructures of the steroid skeleton exist for 7-hydroxy bile salts. While the Δ1,4- variant is well-known from many model organisms, the Δ4,6-variant involving a 7-hydroxysteroid dehydratase as key enzyme has not been systematically studied. Here, combined proteomic, bioinformatic and functional analyses of the Δ4,6-variant in Sphingobium sp. strain Chol11 were performed. They revealed a degradation of the steroid rings similar to the Δ1,4-variant except for the elimination of the 7-OH as a key difference. In contrast, differential production of the respective proteins revealed a putative gene cluster degradation of the C5 carboxylic side chain encoding a CoA-ligase, an acyl-CoA dehydrogenase, a Rieske monooxygenase, and an amidase, but lacking most canonical genes known from other steroid-degrading bacteria. Bioinformatic analyses predicted the Δ4,6-variant to be widespread among the Sphingomonadaceae, which was verified for three type strains which also have the predicted side-chain degradation cluster. A second amidase in the side-chain degradation gene cluster of strain Chol11 was shown to cleave conjugated bile salts while having low similarity to known bile-salt hydrolases. This study signifies members of the Sphingomonadaceae remarkably well-adapted to the utilization of bile salts via a partially distinct metabolic pathway. Importance This study highlights the biochemical diversity of bacterial degradation of steroid compounds, in particular bile salts. Furthermore, it substantiates and advances knowledge of a variant pathway for degradation of steroids by sphingomonads, a group of environmental bacteria that are well-known for their broad metabolic capabilities. Biodegradation of bile salts is a critical process due to the high input of these compounds from manure into agricultural soils and wastewater treatment plants. In addition, these results may also be relevant for the biotechnological production of bile salts or other steroid compounds with pharmaceutical functions.
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Feller FM, Marke G, Drees SL, Wöhlbrand L, Rabus R, Philipp B. Substrate Inhibition of 5β-Δ 4-3-Ketosteroid Dehydrogenase in Sphingobium sp. Strain Chol11 Acts as Circuit Breaker During Growth With Toxic Bile Salts. Front Microbiol 2021; 12:655312. [PMID: 33868213 PMCID: PMC8044976 DOI: 10.3389/fmicb.2021.655312] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/02/2021] [Indexed: 12/12/2022] Open
Abstract
In contrast to many steroid hormones and cholesterol, mammalian bile salts are 5β-steroids, which leads to a bent structure of the steroid core. Bile salts are surface-active steroids excreted into the environment in large amounts, where they are subject to bacterial degradation. Bacterial steroid degradation is initiated by the oxidation of the A-ring leading to canonical Δ4-3-keto steroids with a double bond in the A-ring. For 5β-bile salts, this Δ4-double bond is introduced into 3-keto-bile salts by a 5β-Δ4-ketosteroid dehydrogenase (5β-Δ4-KSTD). With the Nov2c019 protein from bile-salt degrading Sphingobium sp. strain Chol11, a novel 5β-Δ4-KSTD for bile-salt degradation belonging to the Old Yellow Enzyme family was identified and named 5β-Δ4-KSTD1. By heterologous production in Escherichia coli, 5β-Δ4-KSTD function could be shown for 5β-Δ4-KSTD1 as well as the homolog CasH from bile-salt degrading Rhodococcus jostii RHA1. The deletion mutant of 5β-Δ4-kstd1 had a prolonged lag-phase with cholate as sole carbon source and, in accordance with the function of 5β-Δ4-KSTD1, showed delayed 3-ketocholate transformation. Purified 5β-Δ4-KSTD1 was specific for 5β-steroids in contrast to 5α-steroids and converted steroids with a variety of hydroxy groups regardless of the presence of a side chain. 5β-Δ4-KSTD1 showed a relatively low K m for 3-ketocholate, a very high specific activity and pronounced substrate inhibition. With respect to the toxicity of bile salts, these kinetic properties indicate that 5β-Δ4-KSTD1 can achieve fast detoxification of the detergent character as well as prevention of an overflow of the catabolic pathway in presence of increased bile-salt concentrations.
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Affiliation(s)
- Franziska M Feller
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Gina Marke
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Steffen L Drees
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Lars Wöhlbrand
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Ralf Rabus
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Bodo Philipp
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany.,Fraunhofer-Institut für Molekularbiologie und Angewandte Oekologie IME, Schmallenberg, Germany
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Chiang Y, Wei ST, Wang P, Wu P, Yu C. Microbial degradation of steroid sex hormones: implications for environmental and ecological studies. Microb Biotechnol 2020; 13:926-949. [PMID: 31668018 PMCID: PMC7264893 DOI: 10.1111/1751-7915.13504] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 10/09/2019] [Accepted: 10/09/2019] [Indexed: 12/13/2022] Open
Abstract
Steroid hormones modulate development, reproduction and communication in eukaryotes. The widespread occurrence and persistence of steroid hormones have attracted public attention due to their endocrine-disrupting effects on both wildlife and human beings. Bacteria are responsible for mineralizing steroids from the biosphere. Aerobic degradation of steroid hormones relies on O2 as a co-substrate of oxygenases to activate and to cleave the recalcitrant steroidal core ring. To date, two oxygen-dependent degradation pathways - the 9,10-seco pathway for androgens and the 4,5-seco pathways for oestrogens - have been characterized. Under anaerobic conditions, denitrifying bacteria adopt the 2,3-seco pathway to degrade different steroid structures. Recent meta-omics revealed that microorganisms able to degrade steroids are highly diverse and ubiquitous in different ecosystems. This review also summarizes culture-independent approaches using the characteristic metabolites and catabolic genes to monitor steroid biodegradation in various ecosystems.
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Affiliation(s)
- Yin‐Ru Chiang
- Biodiversity Research CenterAcademia SinicaTaipei115Taiwan
| | | | - Po‐Hsiang Wang
- Biodiversity Research CenterAcademia SinicaTaipei115Taiwan
- Present address:
Earth‐Life Science InstituteTokyo Institute of TechnologyTokyoJapan
| | - Pei‐Hsun Wu
- Graduate Institute of Environmental EngineeringNational Taiwan UniversityTaipei106Taiwan
| | - Chang‐Ping Yu
- Graduate Institute of Environmental EngineeringNational Taiwan UniversityTaipei106Taiwan
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Denitrification characterization of dissolved oxygen microprofiles in lake surface sediment through analyzing abundance, expression, community composition and enzymatic activities of denitrifier functional genes. AMB Express 2019; 9:129. [PMID: 31428884 PMCID: PMC6702497 DOI: 10.1186/s13568-019-0855-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
The responses of denitrifiers and denitrification ability to dissolved oxygen (DO) concent in different layers of surface lake sediments are still poorly understood. Here, the optimal denitrification condition was constructed based on response surface methodology (RSM) to analyze the denitrification characteristics of surface sediments. The aerobic zone (AEZ), hypoxic zone (HYZ), up-anoxic zone (ANZ-1) and sub-anoxic zone (ANZ-2) were partitioned based on the oxygen contents, and sediments were collected using a customized-designed sub-millimeter scale sampling device. Integrated real-time quantitative PCR, Illumina Miseq-based sequencing and denitrifying enzyme activities analysis revealed that denitrification characteristics varied among different DO layers. Among the four layers, the DNA abundance and RNA expression levels of norB, nirS and nosZ were the highest at the aerobic layer, hypoxic layer and up-axoic layer, respectively. The hypoxia and up-anaerobic layer were the active nitrogen removal layers, since these two layers displayed the highest DNA abundance, RNA expression level and enzyme activities of denitrification functional genes. The abundance of major denitrifying bacteria showed significant differences among layers, with Azoarcus, Pseudogulbenkiania and Rhizobium identified as the main nirS, nirK and nosZ-based denitrifiers. Pearson’s correlation revealed that the response of denitrifiers to environmental factors differed greatly among DO layers. Furthermore, napA showed higher DNA abundance and RNA expression level in the aerobic and hypoxic layers than anaerobic layers, indicating that aerobic denitrifiers might play important roles at these layers.
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Mendelski MN, Dölling R, Feller FM, Hoffmann D, Ramos Fangmeier L, Ludwig KC, Yücel O, Mährlein A, Paul RJ, Philipp B. Steroids originating from bacterial bile acid degradation affect Caenorhabditis elegans and indicate potential risks for the fauna of manured soils. Sci Rep 2019; 9:11120. [PMID: 31366938 PMCID: PMC6668416 DOI: 10.1038/s41598-019-47476-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 07/15/2019] [Indexed: 02/08/2023] Open
Abstract
Bile acids are steroid compounds from the digestive tracts of vertebrates that enter agricultural environments in unusual high amounts with manure. Bacteria degrading bile acids can readily be isolated from soils and waters including agricultural areas. Under laboratory conditions, these bacteria transiently release steroid compounds as degradation intermediates into the environment. These compounds include androstadienediones (ADDs), which are C19-steroids with potential hormonal effects. Experiments with Caenorhabditis elegans showed that ADDs derived from bacterial bile acid degradation had effects on its tactile response, reproduction rate, and developmental speed. Additional experiments with a deletion mutant as well as transcriptomic analyses indicated that these effects might be conveyed by the putative testosterone receptor NHR-69. Soil microcosms showed that the natural microflora of agricultural soil is readily induced for bile acid degradation accompanied by the transient release of steroid intermediates. Establishment of a model system with a Pseudomonas strain and C. elegans in sand microcosms indicated transient release of ADDs during the course of bile acid degradation and negative effects on the reproduction rate of the nematode. This proof-of-principle study points at bacterial degradation of manure-derived bile acids as a potential and so-far overlooked risk for invertebrates in agricultural soils.
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Affiliation(s)
- M N Mendelski
- Institute of Zoophysiology, University of Münster (WWU), Münster, Germany
| | - R Dölling
- Institute of Zoophysiology, University of Münster (WWU), Münster, Germany
| | - F M Feller
- Institute of Molecular Microbiology and Biotechnology, University of Münster (WWU), Münster, Germany
| | - D Hoffmann
- Institute of Zoophysiology, University of Münster (WWU), Münster, Germany
| | - L Ramos Fangmeier
- Institute of Zoophysiology, University of Münster (WWU), Münster, Germany
| | - K C Ludwig
- Institute of Molecular Microbiology and Biotechnology, University of Münster (WWU), Münster, Germany.,Institute for Pharmaceutical Microbiology, University Hospital Bonn, University of Bonn, Bonn, Germany
| | - O Yücel
- Institute of Molecular Microbiology and Biotechnology, University of Münster (WWU), Münster, Germany
| | - A Mährlein
- Institute of Molecular Microbiology and Biotechnology, University of Münster (WWU), Münster, Germany
| | - R J Paul
- Institute of Zoophysiology, University of Münster (WWU), Münster, Germany
| | - B Philipp
- Institute of Molecular Microbiology and Biotechnology, University of Münster (WWU), Münster, Germany.
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