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Research Project: Characterization of Colonization of Shiga Toxin-producing Escherichia coli (STEC) in Cattle and Strategies for Effective Preharvest Control

Location: Food Safety and Enteric Pathogens Research

Title: A tandem duplication of a 5-bp sequence in the rcsB gene confers biofilm-producing phenotype in Escherichia coli O157:H7 strain 86-24

Author
item Sharma, Vijay
item Bayles, Darrell

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Biofilm formation, which is an important bacterial survival and virulence attribute, is controlled by intricate regulatory networks. Enterohemorrhagic Escherichia coli O157:H7 is an important foodborne pathogen because infections with this agent could lead to hemorrhagic colitis, kidney dysfunction, and even death, especially in children and elderly. Biofilm formation in E. coli O157 is highly variable and many strains lack the ability to produce biofilms. Here we report the genetic basis of the mechanism enabling biofilm formation in E. coli O157:H7 strain 86-24, linked to a foodborne outbreak in 1986. Biofilm-producing E. coli strains bind the Cong red (CR) dye and thus produce red colonies on a CR agar medium. Strain 86-24 does not produce biofilms, produces white colonies on CR medium, but can give rise to red colored colonies on this medium. Comparative genomics of a representative white (NADC 6564) and a red (NADC 6565) isolate revealed highly homologous genomes as expected, except for the presence of some yet uncharacterized SNPs and a tandem duplication of a 5-bp CAGTG sequence in the coding sequence of the rcsB gene. Alignments of the nucleic acid and amino acid sequences of the rcsB genes and RcsB polypeptides encoded by these genes, respectively, in NADC 6564 and NADC 6565 showed that the 5-bp duplication disrupted the rcsB ORF and resulted in the premature truncation of the RcsB protein in NADC 6565. Complementation of strain NADC 6565 with a plasmid encoding a functional RcsB of NADC 6564 restored biofilm formation, Congo red-binding, and stress response phenotypes characteristics of NADC 6564 on strain NADC 6565. These results indicate that mutations in rcsB could lead to emergence of biofilm-producing isolates in E. coli O157:H7 with enhance potential for environmental survival and colonization in the carrier animals.