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Li X, Zhang R, Li J, Liu N, Chen X, Liu Y, Zhao G, Ding K, Yao P, Feng J, Wu Q, Zhu D, Ma Y. Chemo-Enzymatic Strategy for the Efficient Synthesis of Steroidal Drugs with 10α-Methyl Group and a Side Chain at C17-Position from Biorenewable Phytosterols. JACS AU 2024; 4:1356-1364. [PMID: 38665665 PMCID: PMC11040700 DOI: 10.1021/jacsau.3c00688] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/31/2023] [Accepted: 02/28/2024] [Indexed: 04/28/2024]
Abstract
Steroidal pharmaceuticals with a 10α-methyl group or without the methyl group at C10-position are important medicines, but their synthesis is quite challenging, due to that the natural steroidal starting materials usually have a 10β-methyl group which is difficult to be inverted to 10α-methyl group. In this study, 3-((1R,3aS,4S,7aR)-1-((S)-1-hydroxypropan-2-yl)-7a-methyl-5-oxooctahydro-1H-inden-4-yl) propanoic acid (HIP-IPA, 2e) was demonstrated as a valuable intermediate for the synthesis of this kind of active pharmaceutical ingredients (APIs) with a side chain at C17-position. Knockout of a β-hydroxyacyl-CoA dehydrogenase gene and introduction of a sterol aldolase gene into the genetically modified strains of Mycobacterium fortuitum (ATCC 6841) resulted in strains N13Δhsd4AΩthl and N33Δhsd4AΩthl, respectively. Both strains transformed phytosterols into 2e. Compound 2e was produced in 62% isolated yield (25 g) using strain N13Δhsd4AΩthl, and further converted to (3S,3aS,9aS,9bS)-3-acetyl-3a,6-dimethyl-1,2,3,3a,4,5,8,9,9a,9b-decahydro-7H-cyclopenta[a]naphthalen-7-one, which is the key intermediate for the synthesis of dydrogesterone. This study not only overcomes a challenging synthetic problem by enabling an efficient synthesis of dydrogesterone-like steroidal APIs from phytosterols, the well-recognized cheap and readily available biobased raw materials, but also provides insights for redesigning the metabolic pathway of phytosterols to produce other new compounds of relevance to the steroidal pharmaceutical industry.
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Affiliation(s)
- Xuemei Li
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Rui Zhang
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Jianjiong Li
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Na Liu
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Xi Chen
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Yiyin Liu
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Gang Zhao
- CAS
Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai
Institute of Organic Chemistry, Chinese
Academy of Sciences, Shanghai 200032, China
| | - Kai Ding
- CAS
Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai
Institute of Organic Chemistry, Chinese
Academy of Sciences, Shanghai 200032, China
| | - Peiyuan Yao
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Jinhui Feng
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Qiaqing Wu
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Dunming Zhu
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
| | - Yanhe Ma
- National
Engineering Research Center of Industrial Enzymes and Tianjin Engineering
Research Center of Biocatalytic Technology, Key Laboratory of Engineering Biology for Low-carbon Manufacturing,
National Center of Technology Innovation for Synthetic Biology, and
Tianjin Institute of Industrial Biotechnology, Chinese Academy of
Sciences, Tianjin 300308, China
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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 2024:10.1038/s41575-024-00914-3. [PMID: 38575682 DOI: 10.1038/s41575-024-00914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [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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Holert J, Borker A, Nübel LL, Daniel R, Poehlein A, Philipp B. Bacteria use a catabolic patchwork pathway of apparently recent origin for degradation of the synthetic buffer compound TRIS. THE ISME JOURNAL 2024; 18:wrad023. [PMID: 38365256 PMCID: PMC10848231 DOI: 10.1093/ismejo/wrad023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 11/28/2023] [Accepted: 12/06/2023] [Indexed: 02/18/2024]
Abstract
The synthetic buffer compound TRIS (2-amino-2-(hydroxymethyl)propane-1,3-diol) is used in countless applications, and no detailed information on its degradation has been published so far. Herein, we describe the discovery of a complete bacterial degradation pathway for TRIS. By serendipity, a Pseudomonas strain was isolated from sewage sludge that was able to grow with TRIS as only carbon and nitrogen source. Genome and transcriptome analyses revealed two adjacent gene clusters embedded in a mobile genetic element on a conjugative plasmid to be involved in TRIS degradation. Heterologous gene expression revealed cluster I to encode a TRIS uptake protein, a TRIS alcohol dehydrogenase, and a TRIS aldehyde dehydrogenase, catalyzing the oxidation of TRIS into 2-hydroxymethylserine. Gene cluster II encodes a methylserine hydroxymethyltransferase (mSHMT) and a d-serine dehydratase that plausibly catalyze the conversion of 2-hydroxymethylserine into pyruvate. Conjugational plasmid transfer into Pseudomonas putida KT2440 enabled this strain to grow with TRIS and with 2-hydromethylserine, demonstrating that the complete TRIS degradation pathway can be transmitted by horizontal gene transfer. Subsequent enrichments from wastewater purification systems led to the isolation of further TRIS-degrading bacteria from the Pseudomonas and Shinella genera carrying highly similar TRIS degradation gene clusters. Our data indicate that TRIS degradation evolved recently via gene recruitment and enzyme adaptation from multiple independent metabolic pathways, and database searches suggest that the TRIS degradation pathway is now globally distributed. Overall, our study illustrates how engineered environments can enhance the emergence of new microbial metabolic pathways in short evolutionary time scales.
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Affiliation(s)
- Johannes Holert
- Institute for Molecular Microbiology and Biotechnology, Microbial Biotechnology & Ecology Group, University of Münster, Münster, D-48149, Germany
| | - Aron Borker
- Institute for Molecular Microbiology and Biotechnology, Microbial Biotechnology & Ecology Group, University of Münster, Münster, D-48149, Germany
| | - Laura Lucia Nübel
- Institute for Molecular Microbiology and Biotechnology, Microbial Biotechnology & Ecology Group, University of Münster, Münster, D-48149, Germany
| | - Rolf Daniel
- Institute for Microbiology and Genetics, University of Göttingen, Göttingen, D-37077, Germany
| | - Anja Poehlein
- Institute for Microbiology and Genetics, University of Göttingen, Göttingen, D-37077, Germany
| | - Bodo Philipp
- Institute for Molecular Microbiology and Biotechnology, Microbial Biotechnology & Ecology Group, University of Münster, Münster, D-48149, Germany
- Environmental Microbiology, Fraunhofer Institute for Molecular Biology and Applied Ecology, Schmallenberg, D-57392, Germany
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Horinouchi M, Hayashi T. Comprehensive summary of steroid metabolism in Comamonas testosteroni TA441: entire degradation process of basic four rings and removal of C12 hydroxyl group. Appl Environ Microbiol 2023; 89:e0014323. [PMID: 37815361 PMCID: PMC10654043 DOI: 10.1128/aem.00143-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 08/02/2023] [Indexed: 10/11/2023] Open
Abstract
Comamonas testosteroni is one of the representative aerobic steroid-degrading bacteria. We previously revealed the mechanism of steroidal A,B,C,D-ring degradation by C. testosteroni TA441. The corresponding genes are located in two clusters at both ends of a mega-cluster of steroid degradation genes. ORF7 and ORF6 are the only two genes in these clusters, whose function has not been determined. Here, we characterized ORF7 as encoding the dehydrase responsible for converting the C12β hydroxyl group to the C10(12) double bond on the C-ring (SteC), and ORF6 as encoding the hydrogenase responsible for converting the C10(12) double bond to a single bond (SteD). SteA and SteB, encoded just upstream of SteC and SteD, are in charge of oxidizing the C12α hydroxyl group to a ketone group and of reducing the latter to the C12β hydroxyl group, respectively. Therefore, the C12α hydroxyl group in steroids is removed with SteABCD via the C12 ketone and C12β hydroxyl groups. Given the functional characterization of ORF6 and ORF7, we disclose the entire pathway of steroidal A,B,C,D-ring breakdown by C. testosteroni TA441.IMPORTANCEStudies on bacterial steroid degradation were initiated more than 50 years ago, primarily to obtain materials for steroid drugs. Now, their implications for the environment and humans, especially in relation to the infection and the brain-gut-microbiota axis, are attracting increasing attention. Comamonas testosteroni TA441 is the leading model of bacterial aerobic steroid degradation with the ability to break down cholic acid, the main component of bile acids. Bile acids are known for their variety of physiological activities according to their substituent group(s). In this study, we identified and functionally characterized the genes for the removal of C12 hydroxyl groups and provided a comprehensive summary of the entire A,B,C,D-ring degradation pathway by C. testosteroni TA441 as the representable bacterial aerobic degradation process of the steroid core structure.
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Affiliation(s)
- Masae Horinouchi
- Environmental Molecular Biology Laboratory, RIKEN, Saitama, Japan
- Surface and Interface Science Laboratory, RIKEN, Saitama, Japan
| | - Toshiaki Hayashi
- Environmental Molecular Biology Laboratory, RIKEN, Saitama, Japan
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Jin Y, Peng J, Tian W, Chang Z. A Keto Reductase Involved in Steroid Degradation in Mycolicibacterium neoaurum. Chem Biodivers 2023; 20:e202200800. [PMID: 36564340 DOI: 10.1002/cbdv.202200800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 12/23/2022] [Accepted: 12/23/2022] [Indexed: 12/25/2022]
Abstract
Phytosterols can be used by microorganisms as carbon and energy sources and completely degraded into CO2 and H2 O. The catabolic pathway of phytosterols was well characterized in many microorganisms. Blocking the steroid core ring degradation by deletions of fadE30 and fadD3 genes, two important steroid intermediates, 3aα-H-4α-(3'-Propionic acid)-5α-hydroxy-7aβ-methylhexahydro-1-indanone-δ-lactone (sitolactone, or HIL) and 3aα-H-4α-(3'-propionic acid)-7aβ-methylhexahydro-1,5-indanedione (HIP) can be accumulated. They are currently used to synthesize nor-steroid drugs with an α-methyl group or without the methyl group at the C10 -position, such as estrone and norethindrone. In this study, a key gene involved in the bioconversion of HIP to HIL was identified in Mycolicibacterium neoaurum. Through heterologous expression, gene hipR was found to be involved in the reduction of the C5 keto group of HIP to a hydroxy group, leading to spontaneously lactonization into HIL in vitro. Through gene complementation and knockout, HipR functions were verified and two HIP degradation pathways in vivo were elucidated. The finding of this research facilitated the understanding of the metabolic pathway of sterols, and was directly applied to engineering robust production strains by overexpression or knockout of related genes.
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Affiliation(s)
- Ying Jin
- School of Life Science and Biopharmaceuticals, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang, 110016, P. R. China
- Shenyang Botai Pharmaceutical Ltd., 7 Xihe Shibei Street, Tiexi District, Shenyang, 110000, P. R. China
| | - Jinjin Peng
- School of Life Science and Biopharmaceuticals, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang, 110016, P. R. China
| | - Wei Tian
- School of Life Science and Biopharmaceuticals, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang, 110016, P. R. China
| | - Zunxue Chang
- School of Life Science and Biopharmaceuticals, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang, 110016, P. R. China
- Shenyang Botai Pharmaceutical Ltd., 7 Xihe Shibei Street, Tiexi District, Shenyang, 110000, P. R. China
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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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Hsiao TH, Lee TH, Chuang MR, Wang PH, Meng M, Horinouchi M, Hayashi T, Chen YL, Chiang YR. Identification of essential β-oxidation genes and corresponding metabolites for oestrogen degradation by actinobacteria. Microb Biotechnol 2021; 15:949-966. [PMID: 34523795 PMCID: PMC8913865 DOI: 10.1111/1751-7915.13921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 09/01/2021] [Indexed: 11/30/2022] Open
Abstract
Steroidal oestrogens (C18) are contaminants receiving increasing attention due to their endocrine‐disrupting activities at sub‐nanomolar concentrations. Although oestrogens can be eliminated through photodegradation, microbial function is critical for removing oestrogens from ecosystems devoid of sunlight exposure including activated sludge, soils and aquatic sediments. Actinobacteria were found to be key oestrogen degraders in manure‐contaminated soils and estuarine sediments. Previously, we used the actinobacterium Rhodococcus sp. strain B50 as a model microorganism to identify two oxygenase genes, aedA and aedB, involved in the activation and subsequent cleavage of the estrogenic A‐ring respectively. However, genes responsible for the downstream degradation of oestrogen A/B‐rings remained completely unknown. In this study, we employed tiered comparative transcriptomics, gene disruption experiments and mass spectrometry‐based metabolite profile analysis to identify oestrogen catabolic genes. We observed the up‐regulation of thiolase‐encoding aedF and aedK in the transcriptome of strain B50 grown with oestrone. Consistently, two downstream oestrogenic metabolites, 5‐oxo‐4‐norestrogenic acid (C17) and 2,3,4‐trinorestrogenic acid (C15), were accumulated in aedF‐ and aedK‐disrupted strain B50 cultures. Disruption of fadD3 [3aα‐H‐4α(3'‐propanoate)‐7aβ‐methylhexahydro‐1,5‐indanedione (HIP)‐coenzyme A‐ligase gene] in strain B50 resulted in apparent HIP accumulation in oestrone‐fed cultures, indicating the essential role of fadD3 in actinobacterial oestrogen degradation. In addition, we detected a unique meta‐cleavage product, 4,5‐seco‐estrogenic acid (C18), during actinobacterial oestrogen degradation. Differentiating the oestrogenic metabolite profile and degradation genes of actinobacteria and proteobacteria enables the cost‐effective and time‐saving identification of potential oestrogen degraders in various ecosystems through liquid chromatography–mass spectrometry analysis and polymerase chain reaction‐based functional assays.
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Affiliation(s)
- Tsun-Hsien Hsiao
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Tzong-Huei Lee
- Institute of Fisheries Science, National Taiwan University, Taipei, 106, Taiwan
| | - Meng-Rong Chuang
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Po-Hsiang Wang
- Gradaute Institute of Environmental Engineering, National Central University, Taoyuan, 320, Taiwan.,Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan
| | - Menghsiao Meng
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 402, Taiwan
| | - Masae Horinouchi
- Condensed Molecular Materials Laboratory, RIKEN, Saitama, 351-0198, Japan
| | - Toshiaki Hayashi
- Environmental Molecular Biology Laboratory, RIKEN, Saitama, 351-0198, Japan
| | - Yi-Lung Chen
- Department of Microbiology, Soochow University, Taipei, 111, Taiwan
| | - Yin-Ru Chiang
- Biodiversity Research Center, Academia Sinica, Taipei, 115, Taiwan
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Identification of the Coenzyme A (CoA) Ester Intermediates and Genes Involved in the Cleavage and Degradation of the Steroidal C-Ring by Comamonas testosteroni TA441. Appl Environ Microbiol 2021; 87:e0110221. [PMID: 34232729 DOI: 10.1128/aem.01102-21] [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: 11/20/2022] Open
Abstract
Comamonas testosteroni TA441 degrades steroids aerobically via aromatization of the A-ring accompanied by B-ring cleavage, followed by D- and C-ring cleavage. We previously revealed major enzymes and intermediate compounds in A,B-ring cleavage, the β-oxidation cycle of the cleaved B-ring, and partial C,D-ring cleavage. Here, we elucidate the C-ring cleavage and the β-oxidation cycle that follows. ScdL1L2, a 3-ketoacid coenzyme A (CoA) transferase which belongs to the SugarP_isomerase superfamily, was thought to cleave the C-ring of 9-oxo-1,2,3,4,5,6,10,19-octanor-13,17-secoandrost-8(14)-ene-7,17-dioic acid-CoA ester, the key intermediate compound in the degradation of 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid (3aα-H-4α [3'-propionic acid]-7aβ-methylhexahydro-1,5-indanedione; HIP)-CoA ester in our previous study; however, the present study suggested that ScdL1L2 is the isomerase of the derivative with a hydroxyl group at C-14 which cleaves the C-ring. The subsequent ring-cleaved product was indicated to be converted to 4-methyl-5-oxo-octane-1,8-dioic acid-CoA ester mainly by ORF33-encoded CoA-transferase (named ScdJ), followed by dehydrogenation by ORF21- and 22-encoded acyl-CoA dehydrogenase (named ScdM1M2). Then, a water molecule is added by ScdN for further degradation by β-oxidation. ScdN is proposed to catalyze the last reaction in C,D-ring degradation by the enzymes encoded in the steroid degradation gene cluster tesB to tesR. IMPORTANCE Studies on bacterial steroid degradation were initiated more than 50 years ago primarily to obtain materials for steroid drugs. Steroid-degrading bacteria are globally distributed, and the role of bacterial steroid degradation in the environment, as well as in humans, is attracting attention. The overall degradation process of the four steroidal rings has been proposed; however, there is still much to be revealed to understand the complete degradation pathway. This study aimed to uncover the whole steroid degradation process in C. testosteroni, which is one of the most studied representative steroid-degrading bacteria and is suitable for exploring the degradation pathway because the involvement of degradation-related genes can be determined by gene disruption.
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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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10
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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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11
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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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12
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Ibero J, Galán B, Rivero-Buceta V, García JL. Unraveling the 17β-Estradiol Degradation Pathway in Novosphingobium tardaugens NBRC 16725. Front Microbiol 2020; 11:588300. [PMID: 33424788 PMCID: PMC7793797 DOI: 10.3389/fmicb.2020.588300] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 10/30/2020] [Indexed: 11/28/2022] Open
Abstract
We have analyzed the catabolism of estrogens in Novosphingobium tardaugens NBRC 16725, which is able to use endocrine disruptors such as 17β-estradiol, estrone, and estriol as sole carbon and energy sources. A transcriptomic analysis enabled the identification of a cluster of catabolic genes (edc cluster) organized in two divergent operons that are involved in estrogen degradation. We have developed genetic tools for this estrogen-degrading bacterium, allowing us to delete by site-directed mutagenesis some of the genes of the edc cluster and complement them by using expression plasmids to better characterize their precise role in the estrogen catabolism. Based on these results, a catabolic pathway is proposed. The first enzyme of the pathway (17β-hydroxysteroid dehydrogenase) used to transform 17β-estradiol into estrone is encoded out of the cluster. A CYP450 encoded by the edcA gene performs the second metabolic step, i.e., the 4-hydroxylation of estrone in this strain. The edcB gene encodes a 4-hydroxyestrone-4,5-dioxygenase that opens ring A after 4-hydroxylation. The initial steps of the catabolism of estrogens and cholate proceed through different pathways. However, the degradation of estrogens converges with the degradation of testosterone in the final steps of the lower catabolic pathway used to degrade the common intermediate 3aα-H-4α(3′-propanoate)7a-β-methylhexahydro-1,5-indanedione (HIP). The TonB-dependent receptor protein EdcT appears to be involved in estrogen uptake, being the first time that this kind of proteins has been involved in steroid transport.
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Affiliation(s)
- Juan Ibero
- Department of Microbial and Plant Biotechnology, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Beatriz Galán
- Department of Microbial and Plant Biotechnology, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Virginia Rivero-Buceta
- Department of Microbial and Plant Biotechnology, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - José L García
- Department of Microbial and Plant Biotechnology, Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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13
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Steroid Degradation in Comamonas testosteroni TA441: Identification of the Entire β-Oxidation Cycle of the Cleaved B Ring. Appl Environ Microbiol 2019; 85:AEM.01204-19. [PMID: 31375491 DOI: 10.1128/aem.01204-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/28/2019] [Indexed: 11/20/2022] Open
Abstract
Comamonas testosteroni TA441 degrades steroids via aromatization of the A ring, followed by degradation of 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid, mainly by β-oxidation. In this study, we revealed that 7β,9α-dihydroxy-17-oxo-1,2,3,4,10,19-hexanorandrostanoic acid-coenzyme A (CoA) ester is dehydrogenated by (3S)-3-hydroxylacyl CoA-dehydrogenase, encoded by scdE (ORF27), and then the resultant 9α-hydroxy-7,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid-CoA ester is converted by 3-ketoacyl-CoA transferase, encoded by scdF (ORF23). With these results, the whole cycle of β-oxidation on the side chain at C-8 of 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid is clarified; 9-hydroxy-17-oxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid-CoA ester is dehydrogenated at C-6 by ScdC1C2, followed by hydration by ScdD. 7β,9α-Dihydroxy-17-oxo-1,2,3,4,10,19-hexanorandrostanoic acid-CoA ester then is dehydrogenated by ScdE to be converted to 9α-hydroxy-17-oxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid-CoA ester and acetyl-CoA by ScdF. ScdF is an ortholog of FadA6 in Mycobacterium tuberculosis H37Rv, which was reported as a 3-ketoacyl-CoA transferase involved in C ring cleavage. We also obtained results suggesting that ScdF is also involved in C ring cleavage, but further investigation is required for confirmation. ORF25 and ORF26, located between scdF and scdE, encode enzymes belonging to the amidase superfamily. Disrupting either ORF25 or ORF26 did not affect steroid degradation. Among the bacteria having gene clusters similar to those of tesB to tesR, some have both ORF25- and ORF26-like proteins or only an ORF26-like protein, but others do not have either ORF25- or ORF26-like proteins. ORF25 and ORF26 are not crucial for steroid degradation, yet they might provide clues to elucidate the evolution of bacterial steroid degradation clusters.IMPORTANCE Studies on bacterial steroid degradation were initiated more than 50 years ago primarily to obtain materials for steroid drugs. Steroid-degrading bacteria are globally distributed, and the role of bacterial steroid degradation in the environment as well as in relation to human health is attracting attention. The overall aerobic degradation of the four basic steroidal rings has been proposed; however, there is still much to be revealed to understand the complete degradation pathway. This study aims to uncover the whole steroid degradation process in Comamonas testosteroni TA441 as a model of steroid-degrading bacteria. C. testosteroni is one of the most studied representative steroid-degrading bacteria and is suitable for exploring the degradation pathway, because the involvement of degradation-related genes can be determined by gene disruption. Here, we elucidated the entire β-oxidation cycle of the cleaved B ring. This cycle is essential for the following C and D ring cleavage.
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14
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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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15
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Olivera ER, Luengo JM. Steroids as Environmental Compounds Recalcitrant to Degradation: Genetic Mechanisms of Bacterial Biodegradation Pathways. Genes (Basel) 2019; 10:genes10070512. [PMID: 31284586 PMCID: PMC6678751 DOI: 10.3390/genes10070512] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 12/29/2022] Open
Abstract
Steroids are perhydro-1,2-cyclopentanophenanthrene derivatives that are almost exclusively synthesised by eukaryotic organisms. Since the start of the Anthropocene, the presence of these molecules, as well as related synthetic compounds (ethinylestradiol, dexamethasone, and others), has increased in different habitats due to farm and municipal effluents and discharge from the pharmaceutical industry. In addition, the highly hydrophobic nature of these molecules, as well as the absence of functional groups, makes them highly resistant to biodegradation. However, some environmental bacteria are able to modify or mineralise these compounds. Although steroid-metabolising bacteria have been isolated since the beginning of the 20th century, the genetics and catabolic pathways used have only been characterised in model organisms in the last few decades. Here, the metabolic alternatives used by different bacteria to metabolise steroids (e.g., cholesterol, bile acids, testosterone, and other steroid hormones), as well as the organisation and conservation of the genes involved, are reviewed.
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Affiliation(s)
- Elías R Olivera
- Departamento Biología Molecular (Área Bioquímica y Biología Molecular), Universidad de León, 24007 León, Spain.
| | - José M Luengo
- Departamento Biología Molecular (Área Bioquímica y Biología Molecular), Universidad de León, 24007 León, Spain
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16
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High-Quality Whole-Genome Sequence of an Estradiol-Degrading Strain, Novosphingobium tardaugens NBRC 16725. Microbiol Resour Announc 2019; 8:8/11/e01715-18. [PMID: 30938330 PMCID: PMC6424214 DOI: 10.1128/mra.01715-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In this work we report the complete sequence and assembly of the estradiol-degrading bacterium Novosphingobium tardaugens NBRC 16725 genome into a single contig using the Pacific Biosciences RS II system. In this work we report the complete sequence and assembly of the estradiol-degrading bacterium Novosphingobium tardaugens NBRC 16725 genome into a single contig using the Pacific Biosciences RS II system.
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17
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Yücel O, Borgert SR, Poehlein A, Niermann K, Philipp B. The 7α-hydroxysteroid dehydratase Hsh2 is essential for anaerobic degradation of the steroid skeleton of 7α-hydroxyl bile salts in the novel denitrifying bacterium Azoarcus sp. strain Aa7. Environ Microbiol 2019; 21:800-813. [PMID: 30680854 DOI: 10.1111/1462-2920.14508] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/14/2018] [Accepted: 12/14/2018] [Indexed: 12/24/2022]
Abstract
Bile salts are steroid compounds from the digestive tract of vertebrates and enter the environment via defecation. Many aerobic bile-salt degrading bacteria are known but no bacteria that completely degrade bile salts under anoxic conditions have been isolated so far. In this study, the facultatively anaerobic Betaproteobacterium Azoarcus sp. strain Aa7 was isolated that grew with bile salts as sole carbon source under anoxic conditions with nitrate as electron acceptor. Phenotypic and genomic characterization revealed that strain Aa7 used the 2,3-seco pathway for the degradation of bile salts as found in other denitrifying steroid-degrading bacteria such as Sterolibacterium denitrificans. Under oxic conditions strain Aa7 used the 9,10-seco pathway as found in, for example, Pseudomonas stutzeri Chol1. Metabolite analysis during anaerobic growth indicated a reductive dehydroxylation of 7α-hydroxyl bile salts. Deletion of the gene hsh2 Aa7 encoding a 7-hydroxysteroid dehydratase led to strongly impaired growth with cholate and chenodeoxycholate but not with deoxycholate lacking a hydroxyl group at C7. The hsh2 Aa7 deletion mutant degraded cholate and chenodeoxycholate to the corresponding C19 -androstadienediones only while no phenotype change was observed during aerobic degradation of cholate. These results showed that removal of the 7α-hydroxyl group was essential for cleavage of the steroid skeleton under anoxic conditions.
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Affiliation(s)
- Onur Yücel
- Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149Münster, Germany
| | - Sebastian Roman Borgert
- Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149Münster, Germany
| | - Anja Poehlein
- Georg-August-University Goettingen, Institute of Microbiology and Genetics, Department of Genomic and Applied Microbiology and Goettingen Genomics Laboratory, Grisebachstr. 8, 37077, Goettingen, Germany
| | - Karin Niermann
- Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149Münster, Germany
| | - Bodo Philipp
- Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, Corrensstr. 3, 48149Münster, Germany
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18
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Steroid Degradation in Comamonas testosteroni TA441: Identification of Metabolites and the Genes Involved in the Reactions Necessary before D-Ring Cleavage. Appl Environ Microbiol 2018; 84:AEM.01324-18. [PMID: 30194104 DOI: 10.1128/aem.01324-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 07/23/2018] [Indexed: 12/21/2022] Open
Abstract
Bacterial steroid degradation has been studied mainly with Rhodococcus equi (Nocardia restrictus) and Comamonas testosteroni as representative steroid degradation bacteria for more than 50 years. The primary purpose was to obtain materials for steroid drugs, but recent studies showed that many genera of bacteria (Mycobacterium, Rhodococcus, Pseudomonas, etc.) degrade steroids and that steroid-degrading bacteria are globally distributed and found particularly in wastewater treatment plants, the soil, plant rhizospheres, and the marine environment. The role of bacterial steroid degradation in the environment is, however, yet to be revealed. To uncover the whole steroid degradation process in a representative steroid-degrading bacterium, C. testosteroni, to provide basic information for further studies on the role of bacterial steroid degradation, we elucidated the two indispensable oxidative reactions and hydration before D-ring cleavage in C. testosteroni TA441. In bacterial oxidative steroid degradation, A- and B-rings of steroids are cleaved to produce 2-hydroxyhexa-2,4-dienoic acid and 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid. The latter compound was revealed to be degraded to the coenzyme A (CoA) ester of 9α-hydroxy-17-oxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid, which is converted to the CoA ester of 9,17-dioxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid by ORF31-encoded hydroxylacyl dehydrogenase (ScdG), followed by conversion to the CoA ester of 9,17-dioxo-1,2,3,4,5,6,10,19-octanorandrost-8(14)-en-7-oic acid by ORF4-encoded acyl-CoA dehydrogenase (ScdK). Then, a water molecule is added by the ORF5-encoded enoyl-CoA hydratase (ScdY), which leads to the cleavage of the D-ring. The conversion by ScdG is presumed to be a reversible reaction. The elucidated pathway in C. testosteroni TA441 is different from the corresponding pathways in Mycobacterium tuberculosis H37Rv.IMPORTANCE Studies on representative steroid degradation bacteria Rhodococcus equi (Nocardia restrictus) and Comamonas testosteroni were initiated more than 50 years ago primarily to obtain materials for steroid drugs. A recent study showed that steroid-degrading bacteria are globally distributed and found particularly in wastewater treatment plants, the soil, plant rhizospheres, and the marine environment, but the role of bacterial steroid degradation in the environment is yet to be revealed. This study aimed to uncover the whole steroid degradation process in C. testosteroni TA441, in which major enzymes for steroidal A- and B-ring cleavage were elucidated, to provide basic information for further studies on bacterial steroid degradation. C. testosteroni is suitable for exploring the degradation pathway because the involvement of degradation-related genes can be determined by gene disruption. We elucidated the two indispensable oxidative reactions and hydration before D-ring cleavage, which appeared to differ from those present in Mycobacterium tuberculosis H37Rv.
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19
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Functional Characterization of Three Specific Acyl-Coenzyme A Synthetases Involved in Anaerobic Cholesterol Degradation in Sterolibacterium denitrificans Chol1S. Appl Environ Microbiol 2018; 84:AEM.02721-17. [PMID: 29374035 DOI: 10.1128/aem.02721-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 01/21/2018] [Indexed: 12/28/2022] Open
Abstract
The denitrifying betaproteobacterium Sterolibacterium denitrificans Chol1S catabolizes steroids such as cholesterol via an oxygen-independent pathway. It involves enzyme reaction sequences described for aerobic cholesterol and bile acid degradation as well as enzymes uniquely found in anaerobic steroid-degrading bacteria. Recent studies provided evidence that in S. denitrificans, the cholest-4-en-3-one intermediate is oxygen-independently oxidized to Δ4-dafachronic acid (C26-oic acid), which is subsequently activated by a substrate-specific acyl-coenzyme A (acyl-CoA) synthetase (ACS). Further degradation was suggested to proceed via unconventional β-oxidation, where aldolases, aldehyde dehydrogenases, and additional ACSs substitute for classical β-hydroxyacyl-CoA dehydrogenases and thiolases. Here, we heterologously expressed three cholesterol-induced genes that putatively code for AMP-forming ACSs and characterized two of the products as specific 3β-hydroxy-Δ5-cholenoyl-CoA (C24-oic acid)- and pregn-4-en-3-one-22-oyl-CoA (C22-oic acid)-forming ACSs, respectively. A third heterologously produced ATP-dependent ACS was inactive with C26-, C24-, or C22-oic-acids but activated 3aα-H-4α-(3'propanoate)-7aβ-methylhexahydro-1,5-indanedione (HIP) to HIP-CoA, a rather late intermediate of aerobic cholesterol degradation that still contains the CD rings of the sterane skeleton. This work provides experimental evidence that anaerobic steroid degradation proceeds via numerous alternate CoA-ester-dependent or -independent enzymatic reaction sequences as a result of aldolytic side chain and hydrolytic sterane ring C-C bond cleavages. The aldolytic side chain degradation pathway comprising highly exergonic ACSs and aldehyde dehydrogenases is considered to be essential for driving the unfavorable oxygen-independent C26 hydroxylation forward.IMPORTANCE The biological degradation of ubiquitously abundant steroids is hampered by their low solubility and the presence of two quaternary carbon atoms. The degradation of cholesterol by aerobic Actinobacteria has been studied in detail for more than 30 years and involves a number of oxygenase-dependent reactions. In contrast, much less is known about the oxygen-independent degradation of steroids in denitrifying bacteria. In the cholesterol-degrading anaerobic model organism Sterolibacterium denitrificans Chol1S, initial evidence has been obtained that steroid degradation proceeds via numerous alternate coenzyme A (CoA)-ester-dependent/independent reaction sequences. Here, we describe the heterologous expression of three highly specific and characteristic acyl-CoA synthetases, two of which play key roles in the degradation of the side chain, whereas a third one is specifically involved in the B ring degradation. The results obtained shed light into oxygen-independent steroid degradation comprising more than 40 enzymatic reactions.
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Metagenomes Reveal Global Distribution of Bacterial Steroid Catabolism in Natural, Engineered, and Host Environments. mBio 2018; 9:mBio.02345-17. [PMID: 29382738 PMCID: PMC5790920 DOI: 10.1128/mbio.02345-17] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Steroids are abundant growth substrates for bacteria in natural, engineered, and host-associated environments. This study analyzed the distribution of the aerobic 9,10-seco steroid degradation pathway in 346 publically available metagenomes from diverse environments. Our results show that steroid-degrading bacteria are globally distributed and prevalent in particular environments, such as wastewater treatment plants, soil, plant rhizospheres, and the marine environment, including marine sponges. Genomic signature-based sequence binning recovered 45 metagenome-assembled genomes containing a majority of 9,10-seco pathway genes. Only Actinobacteria and Proteobacteria were identified as steroid degraders, but we identified several alpha- and gammaproteobacterial lineages not previously known to degrade steroids. Actino- and proteobacterial steroid degraders coexisted in wastewater, while soil and rhizosphere samples contained mostly actinobacterial ones. Actinobacterial steroid degraders were found in deep ocean samples, while mostly alpha- and gammaproteobacterial ones were found in other marine samples, including sponges. Isolation of steroid-degrading bacteria from sponges confirmed their presence. Phylogenetic analysis of key steroid degradation proteins suggested their biochemical novelty in genomes from sponges and other environments. This study shows that the ecological significance as well as taxonomic and biochemical diversity of bacterial steroid degradation has so far been largely underestimated, especially in the marine environment. Microbial steroid degradation is a critical process for biomass decomposition in natural environments, for removal of important pollutants during wastewater treatment, and for pathogenesis of bacteria associated with tuberculosis and other bacteria. To date, microbial steroid degradation was mainly studied in a few model organisms, while the ecological significance of steroid degradation remained largely unexplored. This study provides the first analysis of aerobic steroid degradation in diverse natural, engineered, and host-associated environments via bioinformatic analysis of an extensive metagenome data set. We found that steroid-degrading bacteria are globally distributed and prevalent in wastewater treatment plants, soil, plant rhizospheres, and the marine environment, especially in marine sponges. We show that the ecological significance as well as the taxonomic and biochemical diversity of bacterial steroid degradation has been largely underestimated. This study greatly expands our ecological and evolutionary understanding of microbial steroid degradation.
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Genome Sequence of the Bile Salt-Degrading Bacterium Novosphingobium sp. Strain Chol11, a Model Organism for Bacterial Steroid Catabolism. GENOME ANNOUNCEMENTS 2018; 6:6/1/e01372-17. [PMID: 29301902 PMCID: PMC5754482 DOI: 10.1128/genomea.01372-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Many bacteria from different phylogenetic groups are able to degrade eukaryotic steroid compounds, but the underlying metabolic pathways are still not well understood. Novosphingobium sp. strain Chol11 is a steroid-degrading alphaproteobacterium. Its genome sequence reveals that it lacks several genes for steroid degradation known to exist in other model organisms.
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A Novel Steroid-Coenzyme A Ligase from Novosphingobium sp. Strain Chol11 Is Essential for an Alternative Degradation Pathway for Bile Salts. Appl Environ Microbiol 2017; 84:AEM.01492-17. [PMID: 29054875 DOI: 10.1128/aem.01492-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 10/06/2017] [Indexed: 02/05/2023] Open
Abstract
Bile salts such as cholate are steroid compounds with a C5 carboxylic side chain and occur ubiquitously in vertebrates. Upon their excretion into soils and waters, bile salts can serve as growth substrates for diverse bacteria. Novosphingobium sp. strain Chol11 degrades 7-hydroxy bile salts via 3-keto-7-deoxy-Δ4,6 metabolites by the dehydration of the 7-hydroxyl group catalyzed by the 7α-hydroxysteroid dehydratase Hsh2. This reaction has not been observed in the well-studied 9-10-seco degradation pathway used by other steroid-degrading bacteria indicating that strain Chol11 uses an alternative pathway. A reciprocal BLASTp analysis showed that known side chain degradation genes from other cholate-degrading bacteria (Pseudomonas stutzeri Chol1, Comamonas testosteroni CNB-2, and Rhodococcus jostii RHA1) were not found in the genome of strain Chol11. The characterization of a transposon mutant of strain Chol11 showing altered growth with cholate identified a novel steroid-24-oyl-coenzyme A ligase named SclA. The unmarked deletion of sclA resulted in a strong growth rate decrease with cholate, while growth with steroids with C3 side chains or without side chains was not affected. Intermediates with a 7-deoxy-3-keto-Δ4,6 structure, such as 3,12-dioxo-4,6-choldienoic acid (DOCDA), were shown to be likely physiological substrates of SclA. Furthermore, a novel coenzyme A (CoA)-dependent DOCDA degradation metabolite with an additional double bond in the side chain was identified. These results support the hypothesis that Novosphingobium sp. strain Chol11 harbors an alternative pathway for cholate degradation, in which side chain degradation is initiated by the CoA ligase SclA and proceeds via reaction steps catalyzed by so-far-unknown enzymes different from those of other steroid-degrading bacteria.IMPORTANCE This study provides further evidence of the diversity of metabolic pathways for the degradation of steroid compounds in environmental bacteria. The knowledge about these pathways contributes to the understanding of the CO2-releasing part of the global C cycle. Furthermore, it is useful for investigating the fate of pharmaceutical steroids in the environment, some of which may act as endocrine disruptors.
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A fluorescent, supramolecular chemosensor to follow steroid depletion in bacterial cultures. Anal Bioanal Chem 2017; 409:6485-6494. [DOI: 10.1007/s00216-017-0593-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/13/2017] [Accepted: 08/18/2017] [Indexed: 02/07/2023]
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Zhang Y, Liu H, Li L, Ai M, Gong Z, He Y, Dong Y, Xu S, Wang J, Jin B, Liu J, Teng Z. Cholecystectomy can increase the risk of colorectal cancer: A meta-analysis of 10 cohort studies. PLoS One 2017; 12:e0181852. [PMID: 28771518 PMCID: PMC5542607 DOI: 10.1371/journal.pone.0181852] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 07/07/2017] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE This study aimed to elucidate the effects of cholecystectomy on the risk of colorectal cancer (CRC) by conducting a meta-analysis of 10 cohort studies. METHODS The eligible cohort studies were selected by searching the PubMed and EMBASE databases from their origination to June 30, 2016, as well as by consulting the reference lists of the selected articles. Two authors individually collected the data from the 10 papers. When the data showed marked heterogeneity, we used a random-effects model to estimate the overall pooled risk; otherwise, a fixed effects model was employed. RESULTS The final analysis included ten cohort studies. According to the Newcastle-Ottawa Scale (NOS), nine papers were considered high quality. After the data of these 9 studies were combined, an increased risk of CRC was found among the individuals who had undergone cholecystectomy (risk ratio (RR) 1.22; 95% confidence interval (CI) 1.08-1.38). In addition, we also found a promising increased risk for colon cancer (CC) (RR 1.30, 95% CI 1.07-1.58), but no relationship between cholecystectomy and rectum cancer (RC) (RR 1.09; 95% CI 0.89-1.34) was observed. Additionally, in the sub-group analysis of the tumor location in the colon, a positive risk for ascending colon cancer (ACC) was found (RR 1.18, 95% CI 1.11-1.26). After combining the ACC, transverse colon cancer (TCC), sigmoid colon cancer (SCC) and descending colon cancer (DCC) patients, we found a positive relationship with cholecystectomy (RR 1.18, 95% CI 1.11-1.26). Furthermore, after combining the ACC and DCC patients, we also found a positive relationship with cholecystectomy (RR 1.28; 95% CI 1.11-1.26) in the sub-group analysis. In an additional sub-group analysis of patients from Western countries, there was a positive relationship between cholecystectomy and the risk of CRC (RR 1.20; 95% CI 1.05-1.36). Furthermore, a positive relationship between female gender and CRC was also found (RR 1.17; 95% CI 1.03-1.34). However, there was no relationship between gender and CC or RC. Furthermore, no publication bias was observed, and the sensitivity analysis indicated stable results. CONCLUSIONS This meta-analysis of 10 cohort studies revealed that cholecystectomy is associated with an increased risk for CRC, CC and ACC, particularly in Western countries. No relationship between cholecystectomy and RC was observed. There was no relationship between gender and either CC or RC, but a positive relationship between female gender and CRC was observed.
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Affiliation(s)
- Yong Zhang
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Hao Liu
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Li Li
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Min Ai
- School of Public Health, Dali University, Dali, Yunnan, China
| | - Zheng Gong
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Yong He
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Yunlong Dong
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Shuanglan Xu
- Department of Respiratory Medicine, The Affiliated Yanan Hospital of Kunming Medical University, Kunming, Yunnan, China
| | - Jun Wang
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Bo Jin
- Department of General Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Jianping Liu
- Department of Science and Education, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
| | - Zhaowei Teng
- Department of Orthopedic Surgery, The 6th Affiliated Hospital of Kunming Medical University, The People’s Hospital of Yuxi City, Yuxi, Yunnan, China
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Yücel O, Drees S, Jagmann N, Patschkowski T, Philipp B. An unexplored pathway for degradation of cholate requires a 7α-hydroxysteroid dehydratase and contributes to a broad metabolic repertoire for the utilization of bile salts in N
ovosphingobium
sp. strain Chol11. Environ Microbiol 2016; 18:5187-5203. [DOI: 10.1111/1462-2920.13534] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/15/2016] [Indexed: 01/04/2023]
Affiliation(s)
- Onur Yücel
- Westfälische Wilhelms-Universität Münster Institut für Molekulare Mikrobiologie und Biotechnologie; Münster 48149 Germany
| | - Steffen Drees
- Westfälische Wilhelms-Universität Münster Institut für Molekulare Mikrobiologie und Biotechnologie; Münster 48149 Germany
| | - Nina Jagmann
- Westfälische Wilhelms-Universität Münster Institut für Molekulare Mikrobiologie und Biotechnologie; Münster 48149 Germany
| | - Thomas Patschkowski
- Centrum für Biotechnologie - CeBiTec; Universität Bielefeld; Bielefeld 33501 Germany
| | - Bodo Philipp
- Westfälische Wilhelms-Universität Münster Institut für Molekulare Mikrobiologie und Biotechnologie; Münster 48149 Germany
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Abstract
Steroids are ubiquitous in natural environments and are a significant growth substrate for microorganisms. Microbial steroid metabolism is also important for some pathogens and for biotechnical applications. This study delineated the distribution of aerobic steroid catabolism pathways among over 8,000 microorganisms whose genomes are available in the NCBI RefSeq database. Combined analysis of bacterial, archaeal, and fungal genomes with both hidden Markov models and reciprocal BLAST identified 265 putative steroid degraders within only Actinobacteria and Proteobacteria, which mainly originated from soil, eukaryotic host, and aquatic environments. These bacteria include members of 17 genera not previously known to contain steroid degraders. A pathway for cholesterol degradation was conserved in many actinobacterial genera, particularly in members of the Corynebacterineae, and a pathway for cholate degradation was conserved in members of the genus Rhodococcus. A pathway for testosterone and, sometimes, cholate degradation had a patchy distribution among Proteobacteria. The steroid degradation genes tended to occur within large gene clusters. Growth experiments confirmed bioinformatic predictions of steroid metabolism capacity in nine bacterial strains. The results indicate there was a single ancestral 9,10-seco-steroid degradation pathway. Gene duplication, likely in a progenitor of Rhodococcus, later gave rise to a cholate degradation pathway. Proteobacteria and additional Actinobacteria subsequently obtained a cholate degradation pathway via horizontal gene transfer, in some cases facilitated by plasmids. Catabolism of steroids appears to be an important component of the ecological niches of broad groups of Actinobacteria and individual species of Proteobacteria. Steroids are ubiquitous growth substrates for environmental and pathogenic bacteria, and bacterial steroid metabolism has important pharmaceutical and health applications. To date, the genetics and biochemistry of microbial steroid degradation have mainly been studied in a few model bacteria, and the diversity of this metabolism remains largely unexplored. Here, we provide a bioinformatically derived perspective of the taxonomic distribution of aerobic microbial steroid catabolism pathways. We identified several novel steroid-degrading bacterial groups, including ones from marine environments. In several cases, we confirmed bioinformatic predictions of metabolism in cultures. We found that cholesterol and cholate catabolism pathways are highly conserved among certain actinobacterial taxa. We found evidence for horizontal transfer of a pathway to several proteobacterial genera, conferring testosterone and, sometimes, cholate catabolism. The results of this study greatly expand our ecological and evolutionary understanding of microbial steroid metabolism and provide a basis for better exploiting this metabolism for biotechnology.
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