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Applied and Environmental Microbiology, August 2001, p. 3476-3480, Vol. 67, No. 8
Department of Microbiology, University of
Tennessee, Knoxville, Tennessee 37996-0845
Received 4 December 2000/Accepted 8 May 2001
Bacteria of numerous species isolated from the human
gastrointestinal tract express bile salt hydrolase (BSH) activity. How this activity contributes to functions of the microorganisms in the
gastrointestinal tract is not known. We tested the hypothesis that a
BSH protects the cells that produce it from the toxicity of conjugated
bile salts. Forty-nine strains of numerous Lactobacillus spp. were assayed to determine their capacities to express BSH activities (taurodeoxycholic acid [TDCA] hydrolase and taurocholic acid [TCA] hydrolase activities) and their capacities to resist the
toxicity of a conjugated bile acid (TDCA). Thirty of these strains had
been isolated from the human intestine, 15 had been recovered from
dairy products, and 4 had originated from other sources. Twenty-six of
the strains expressed both TDCA hydrolase and TCA hydrolase
activities. One strain that expressed TDCA hydrolase activity did not
express TCA hydrolase activity. Conversely, in one strain for which the
assay for TDCA hydrolase activity gave a negative result there was
evidence of TCA hydrolase activity. Twenty-five of the strains were
found to resist the toxicity of TDCA. Fourteen of these strains were of
human origin, nine were from dairy products, and two were from other
sources. Of the 26 strains expressing both TDCA hydrolase and TCA
hydrolase activities, 15 were resistant to TDCA toxicity, 6 were
susceptible, and 5 gave inconclusive results. Of the 17 strains that
gave negative results for either of the enzymes, 7 were resistant to
the toxicity, 9 were susceptible, and 1 gave inconclusive results.
These findings do not support the hypothesis tested. They suggest,
however, that BSH activity is important at some level for lactobacillus
colonization of the human intestine.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.8.3476-3480.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Bile Salt Hydrolase Activity and Resistance to
Toxicity of Conjugated Bile Salts Are Unrelated Properties in
Lactobacilli
*
Corresponding author. Mailing address: Department of
Microbiology, M409 Walters Life Sciences Building, University of
Tennessee, Knoxville, TN 37996-0845. Phone: (865) 974-4015. Fax:
(865) 974-4007. E-mail: dsavage1{at}utk.edu.
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