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United States Department of Agriculture

Agricultural Research Service

Research Project: FUNCTIONAL FOOD DEVELOPMENT BY MICROBIAL BIOTECHNOLOGY

Location: Dairy and Functional Foods

Title: Genetic analysis of a novel plasmid encoded durancin locus in Enterococcus durans 41D

Authors
item Du, Llihui -
item Somkuti, George
item Renye, John

Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2011
Publication Date: N/A

Technical Abstract: Enterococcus durans is commonly found in the intestinal tract in humans and animals and several strains are known to produce bacteriocins. Durancin GL, a novel bacteriocin of Enterococcus durans 41D with antilisterial activity was isolated from artisanal cheese samples and its genetic determinants were characterized. The bacteriocin operon included the structural (durA) and immunity (durB) genes among the 9 putative ORFs identified on pDGL1, an 8.3-kb plasmid which was fully sequenced. The deduced DurA protein was a 71-amino acid peptide with 74% identity to the class II bacteriocin BacA of E. faecalis. DurA had a potential signal peptidase cleavage site indicating the involvement of a sec-dependent transport system in yielding a 7.97 kb mature peptide. The mature DurA peptide had the typical structure of subclass IIa bacteriocins, including a conserved YYGNG motif and a hydrophobic C-terminal region. The immunity gene (durB) encoded a 94-amino acid peptide with 85% identity to the BacB immunity gene. The minimum requirement for durancin GL production was defined by translationally fusing a 547 bp fragment containing the durAB genes with the Streptococcus thermophilus chromosomal promoter P2201 by PCR, and subcloning in vector pMEU5a. Isolates of the yogurt starter culture S. thermophilus electrotransformed with the recombinant plasmid pMEU5a-1 secreted durancin GL into the medium and inhibited the growth of Listeria. The results showed the possibility of transferring the durancin GL gene into food-grade lactic acid bacteria to serve as the source of a natural bioprotective agent for Listeria control.

Last Modified: 11/28/2014
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