Open AccessCellodextrin Utilization by Bifidobacterium breve UCC2003
Author(s) -
Karina Pokusaeva,
Mary O’Connell Motherway,
Aldert Zomer,
John MacSharry,
Gerald F. Fitzgerald,
Douwe van Sinderen
Publication year - 2011
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.01786-10
Subject(s) - bifidobacterium breve , cellobiose , operon , gene cluster , biochemistry , biology , mutant , chemistry , iron–sulfur cluster , gene , hydrolysis , cellulase , enzyme , bifidobacterium , fermentation , lactobacillus
Cellodextrins, the incomplete hydrolysis products from insoluble cellulose, are accessible as a carbon source to certain members of the human gut microbiota, such asBifidobacterium breve UCC2003. Transcription of thecldEFGC gene cluster ofB. breve UCC2003 was shown to be induced upon growth on cellodextrins, implicating this cluster in the metabolism of these sugars. Phenotypic analysis of aB. breve UCC2003::cldE insertion mutant confirmed that thecld gene cluster is exclusively required for cellodextrin utilization by this commensal. Moreover, our results suggest that transcription of thecld cluster is controlled by a LacI-type regulator encoded bycldR , located immediately upstream ofcldE . Gel mobility shift assays using purified CldRHis (produced by the incorporation of a His12 -encoding sequence into the 3′ end of thecldC gene) indicate that thecldEFGC promoter is subject to negative control by CldRHis , which binds to two inverted repeats. Analysis by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) of medium samples obtained during growth ofB. breve UCC2003 on a mixture of cellodextrins revealed its ability to utilize cellobiose, cellotriose, cellotetraose, and cellopentaose, with cellotriose apparently representing the preferred substrate. ThecldC gene of thecld operon ofB. breve UCC2003 is, to the best of our knowledge, the first described bifidobacterial β-glucosidase exhibiting hydrolytic activity toward various cellodextrins.