Fukiya Satoru, Arata Miki, Kawashima Hiroko, Yoshida Daisuke, Kaneko Maki, Minamida Kimiko, Watanabe Jun, Ogura Yoshio, Uchida Kiyohisa, Itoh Kikuji, Wada Masaru, Ito Susumu, Yokota Atsushi
Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan.
FEMS Microbiol Lett. 2009 Apr;293(2):263-70. doi: 10.1111/j.1574-6968.2009.01531.x. Epub 2009 Feb 23.
Secondary bile acid-producing bacteria were isolated from human feces to improve our appreciation of the functional diversity and redundancy of the intestinal microbiota. In total, 619 bacterial colonies were isolated using a nutrient-poor agar medium and the level of secondary bile acid formation was examined in each by a liquid culture, followed by thin-layer chromatography. Of five strains analyzed by 16S rRNA gene sequencing and biochemical testing, one was identified as Bacteroides intestinalis AM-1, which was not previously recognized as a secondary bile-acid producer. GC-MS revealed that B. intestinalis AM-1 converts cholic acid (CA) and chenodeoxycholic acid into their 7-oxo derivatives, 7-oxo-deoxycholic acid (7-oxo-DCA) and 7-oxo-lithocholic acid, respectively. Thus, B. intestinalis AM-1 possesses 7alpha-hydroxysteroid dehydrogenase (7alpha-HSDH) activity. In liquid culture, B. intestinalis AM-1 showed a relatively higher productivity of 7-oxo-DCA than Escherichia coli HB101 and Bacteroides fragilis JCM11019(T), which are known to possess 7alpha-HSDH activity. The level of 7alpha-HSDH activity was higher in B. intestinalis AM-1 than in the other two strains under the conditions tested. The 7alpha-HSDH activity in each of the three strains is not induced by CA; instead, it is regulated in a growth phase-dependent manner.
从人类粪便中分离出产生次级胆汁酸的细菌，以增进我们对肠道微生物群功能多样性和冗余性的认识。总共使用营养贫乏的琼脂培养基分离出619个细菌菌落，并通过液体培养检查每个菌落中次级胆汁酸的形成水平，随后进行薄层色谱分析。通过16S rRNA基因测序和生化测试分析的五株菌株中，有一株被鉴定为肠道拟杆菌AM-1，它以前未被认为是次级胆汁酸生产者。气相色谱-质谱联用（GC-MS）分析表明，肠道拟杆菌AM-1将胆酸（CA）和鹅去氧胆酸分别转化为它们的7-氧代衍生物，即7-氧代脱氧胆酸（7-氧代-DCA）和7-氧代石胆酸。因此，肠道拟杆菌AM-1具有7α-羟基类固醇脱氢酶（7α-HSDH）活性。在液体培养中，肠道拟杆菌AM-1产生7-氧代-DCA的能力相对高于已知具有7α-HSDH活性的大肠杆菌HB101和脆弱拟杆菌JCM11019(T)。在所测试的条件下，肠道拟杆菌AM-1中的7α-HSDH活性水平高于其他两株菌株。这三株菌株中的7α-HSDH活性均不受CA诱导；相反，它是以生长阶段依赖的方式进行调节的。
