|Wang, Lili - Shenyang Agricultural University|
|Nichols-russell, Lydia - University Of Maryland|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2015
Publication Date: 7/1/2015
Citation: Nagy, A., Mowery, J.D., Bauchan, G.R., Wang, L., Nichols-Russell, L., Nou, X. 2015. Role of major surface structures of Escherichia coli O157:H7 in initial attachment to biotic and abiotic surfaces. Applied and Environmental Microbiology. 81:4720-4727.
Interpretive Summary: Enterohemorrhagic Escherichia coli (EHEC) infections can cause a wide range of human diseases. Escherichia coli O157:H7, a common EHEC strain,can adapt to unfavorable environmental conditions by forming biofilms. The formation of biofilms starts with early attachment events: bacteria sense, recognize, and respond to various environmental conditions that trigger the transformation from planktonic to sessile form. The aim of this study was to investigate the role of several major cell surface structures in interactions with food and environmental matrices during the early stages of biofilm formation. Mutant strains of Escherichia coli O157:H7 were generated which lacked specific surface structures (pili, fimbria, flagella). Subsequent attachement studies demonstrated that wildtype strains attached more firmly to spinach or glass than mutant strains. Furthermore, growth of wildtype strains at lower temperatures (25 and 4 oC) resulted in enhanced expression of surface structures. Our results show that filamentous surface structures of Escherichia coli play an important role in early stages of fresh produce leaf colonization and biofilm formation. The pili, flagella and other surface structures lay the foundation for a stable, mature biofilm, where the bacteria are sheltered from hostile environmental factors as well as industrial decontaminantsThis information will be useful to other scientists.
Technical Abstract: Infection by human pathogens through fresh, minimally processed produce and solid plant-derived foods is a major concern of U.S. and global food industry and public health services. The enterohemorrhagic Escherichia coli O157:H7 is a frequent and potent food borne pathogen that causes severe disease in humans. Biofilms formed by E. coli O157:H7 facilitates cross-contamination by sheltering pathogens and protecting them from cleaning and sanitation operations. The objective of this research was to determine the role several surface structures of E. coli O157:H7 play in adherence to biotic and abiotic surfaces, which is the first step of biofilm formation. A set of isogenic deletion mutants lacking major surface structures was generated. The mutant strains were inoculated on freshly spinach and glass surfaces, and their capability to adhere was assessed by adherence assays and fluorescent microscopy methods. Our results show that filament-deficient mutants bind to the spinach leaves and glass surface less strongly compared to the wild type strain. We mimicked the switch to natural environment by decreasing the temperature from 37 oC to 25 oC and 4 oC. The upregulation of the expression of target genes upon temperature shift also underlines the importance of filamental structures in adaptation of E. coli to the new environment. We conclude that pili, flagella and other filamental structures are critical factors in the establishment of biofilms. A better understanding of the specific roles of these filamental structures in early stages of biofilm formation can help to prevent cross-contaminations and food borne disease outbreaks.