title: Substrate uptake and subcellular compartmentation of anoxic cholesterol catabolism in Sterolibacterium denitrificans.
abstract: Cholesterol catabolism by actinobacteria has been extensively studied. In contrast, the uptake and catabolism of cholesterol by Gram-negative species are poorly understood. Here, we investigated microbial cholesterol catabolism at the subcellular level. (13)C metabolomic analysis revealed that anaerobically grown Sterolibacterium denitrificans, a β-proteobacterium, adopts an oxygenase-independent pathway to degrade cholesterol. S. denitrificans cells did not produce biosurfactants upon growth on cholesterol and exhibited high cell surface hydrophobicity. Moreover, S. denitrificans did not produce extracellular catabolic enzymes to transform cholesterol. Accordingly, S. denitrificans accessed cholesterol by direction adhesion. Cholesterol is imported through the outer membrane via a putative FadL-like transport system, which is induced by neutral sterols. The outer membrane steroid transporter is able to selectively import various C27 sterols into the periplasm. S. denitrificans spheroplasts exhibited a significantly higher efficiency in cholest-4-en-3-one-26-oic acid uptake than in cholesterol uptake. We separated S. denitrificans proteins into four fractions, namely the outer membrane, periplasm, inner membrane, and cytoplasm, and we observed the individual catabolic reactions within them. Our data indicated that, in the periplasm, various periplasmic and peripheral membrane enzymes transform cholesterol into cholest-4-en-3-one-26-oic acid. The C27 acidic steroid is then transported into the cytoplasm, in which side-chain degradation and the subsequent sterane cleavage occur. This study sheds light into microbial cholesterol metabolism under anoxic conditions.
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Ching-Wen
authors.initials: CW
authors.lastname: Lin
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Po-Hsiang
authors.initials: PH
authors.lastname: Wang
authors.affiliation: the Life Sciences Department, Biotechnology Program, College of Graduate Studies, Arabian Gulf University, Manama 329, Kingdom of Bahrain.
authors.forename: Wael
authors.initials: W
authors.lastname: Ismail
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Tsai
authors.affiliation: the Life Sciences Department, Biotechnology Program, College of Graduate Studies, Arabian Gulf University, Manama 329, Kingdom of Bahrain.
authors.forename: Ashraf
authors.initials: A
authors.lastname: El Nayal
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Chia-Ying
authors.initials: CY
authors.lastname: Yang
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Fu-Chun
authors.initials: FC
authors.lastname: Yang
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and.
authors.forename: Chia-Hsiang
authors.initials: CH
authors.lastname: Wang
authors.affiliation: From the Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan and yinru915@gate.sinica.edu.tw.
authors.forename: Yin-Ru
authors.initials: YR
authors.lastname: Chiang
mesh_terms: D000693:Anaerobiosis; D002250:Carbon Radioisotopes / Q000737:chemistry; D015687:Cell Hypoxia; D002783:Cholestenones / Q000737:chemistry / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000378:metabolism*; D008066:Lipolysis; D008660:Metabolism / Q000235:genetics; D010084:Oxidation-Reduction; D019897:Periplasm / Q000201:enzymology; D043362:Rhodocyclaceae / Q000201:enzymology; D013261:Sterols / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002250:Carbon Radioisotopes; D002783:Cholestenones; D013261:Sterols; C000475:cholest-4-en-3-one; D002784:Cholesterol
keywords: Bacterial Metabolism; Cholesterol; Cholesterol Metabolism; Gram-negative Bacteria; Metabolomics; Steroid Hormone; Subcellular Fractionation