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Allelic variation of bile salt hydrolase genes in Lactobacillus salivarius does not determine bile resistance levels

DOI: 10.1128/JB.00506-09 DOI Help
PMID: 19592587 PMID Help

Authors: Fang Fang (UCC) , Y Li , M Bumann , E Raftis , P Casey , J Cooney , P O'Toole , Martin A. Walsh (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal of Bacteriology , VOL 191 (18) , PAGES 5743 5757

State: Published (Approved)
Published: September 2009

Abstract: Commensal lactobacilli frequently produce bile salt hydrolase (Bsh) enzymes whose roles in intestinal survival are unclear. Twenty-six Lactobacillus salivarius strains from different sources all harbored a bsh1 allele on their respective megaplasmids. This allele was related to the plasmid-borne bsh1 gene of the probiotic strain UCC118. A second locus (bsh2) was found in the chromosomes of two strains that had higher bile resistance levels. Four Bsh1-encoding allele groups were identified, defined by truncations or deletions involving a conserved residue. In vitro analyses showed that this allelic variation was correlated with widely varying bile deconjugation phenotypes. Despite very low activity of the UCC118 Bsh1 enzyme, a mutant lacking this protein had significantly lower bile resistance, both in vitro and during intestinal transit in mice. However, the overall bile resistance phenotype of this and other strains was independent of the bsh1 allele type. Analysis of the L. salivarius transcriptome upon exposure to bile and cholate identified a multiplicity of stress response proteins and putative efflux proteins that appear to broadly compensate for, or mask, the effects of allelic variation of bsh genes. Bsh enzymes with different bile-degrading kinetics, though apparently not the primary determinants of bile resistance in L. salivarius, may have additional biological importance because of varying effects upon bile as a signaling molecule in the host.

Journal Keywords: Bile Salt Hydrolase; Probiotic; Gut

Subject Areas: Food Science, Biology and Bio-materials, Medicine

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Added On: 16/04/2010 12:17

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