Different bacterial strategies to degrade taurocholate
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ORIGINAL PAPER
DiVerent bacterial strategies to degrade taurocholate Verena Rösch · Karin Denger · David Schleheck · Theo H. M. Smits · Alasdair M. Cook
Received: 25 October 2007 / Revised: 31 January 2008 / Accepted: 18 February 2008 / Published online: 5 March 2008 © Springer-Verlag 2008
Abstract Aerobic enrichment cultures with taurocholate or alkanesulfonates as sole sources of carbon and energy for growth were successful and yielded nine bacterial isolates, all of which utilized taurocholate. Growth was complex and involved not only many, usually transient, excretion products but also sorption of taurocholate and cholate to cells. Three metabolic strategies to dissimilate taurocholate were elucidated, all of which involved bile salt hydrolase cleaving taurocholate to cholate and taurine. Comamonas testosteroni KF-1 utilized both the taurine and the cholate moieties for growth. Pseudomonas spp., e.g. strain TAC-K3 and Rhodococcus equi TAC-A1 grew with the cholate moiety and released taurine quantitatively. Delftia acidovorans SPH-1 utilized the taurine moiety and released cholate. Keywords Bile salt hydrolase · Comamonas testosteroni · Delftia acidovorans · Desulfonation · Excretion of cholate · Excretion of taurine · Pseudomonas spp. · Taurine dissimilation Communicated by Walter Reinecke. V. Rösch · K. Denger · D. Schleheck · T. H. M. Smits · A. M. Cook (&) Department of Biology, The University, 78457 Konstanz, Germany e-mail: [email protected] D. Schleheck School of Biotechnology and Biomolecular Sciences and Centre for Marine Biofouling and Bio-Innovation, University of New South Wales, Sydney, NSW 2052, Australia T. H. M. Smits Agroscope Changins-Wädenswil ACW, Swiss Federal Research Station, Schloss, Postfach 185, 8820 Wädenswil, Switzerland
Introduction Taurocholate (Fig. 1) is a bile salt, which is probably best known as an emulsiWer involved in the uptake of fats from the gut (e.g. Berg et al. 2007). A portion of this taurocholate is excreted in the faeces (e.g. Metzler 2003) in signiWcant amounts (Hylemon and Harder 1998), so the compound can be considered as a signiWcant source of available carbon in terrestrial and aquatic environments. The role of taurocholate as a selective inhibitor in microbial growth media (e.g. MacConkey Agar) has been known for about a century (MacConkey 1900); the compound is also used in other selective media, e.g. to improve the recovery of clostridial spores (Buggy et al. 1985). Further, considerable research has been invested in bile salt hydrolase (Bsh: also termed choloylglycine hydrolase) [EC 3.5.1.24] and its inferred role in (1) detoxifying the anti-microbial activity of, e.g. taurocholate to cholate and taurine in the gut, (2) pathogenicity, or (3) probiotics (e.g. Moser and Savage 2001; Sue et al. 2003; McAuliVe et al. 2005; Kumar et al. 2006; Delpino et al. 2007). The enzyme is generated from a precursor protein, that is not autocatalytically cleaved to maturity (Kumar et al. 2006), but that often contains a putative leader peptide, which indicates
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