Competitive interactions between food-borne pathogens within mixed-species biofilms.

Prentice, Emma Louise (2021) Competitive interactions between food-borne pathogens within mixed-species biofilms. Masters thesis, University of East Anglia.

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Within nature bacteria primarily exist as biofilms; polymicrobial aggregates surrounded by a protective matrix. Biofilms are more tolerant to antimicrobials than their planktonic counterparts due to their ability to produce growth-arrested persister cells. Many infections have a biofilm component that makes treatment difficult and results in recurrent, chronic infections. Biofilms often comprise multiple species which promotes cooperation and competition between cells that results in rapid adaptation to an environment. Competition in multispecies biofilms is high due to limited space and resources and bacteria can employ a variety of mechanisms to inhibit or kill competitors. This study used a biofilm evolution model, using glass beads as a substrate for biofilm formation, to identify interactions between a food isolate of E. coli (EC166 of ST10) and three Salmonella strains. S. Typhimurium and S. Enteritidis growth was inhibited in the presence of E. coli EC166 biofilms however, all three strains survived with E. coli EC166 under planktonic conditions, suggesting a biofilm-dependent mechanism of inhibition. When added to pre-formed E. coli EC166 biofilms, growth of all three Salmonella strains was reduced suggesting an active mechanism of inhibition, induced by the presence of Salmonella, rather than general competition for resources. Furthermore, immediately after inoculation and passaging, all three Salmonella species were more abundant than E. coli EC166 in a multispecies biofilm, demonstrating that Salmonella initially colonises the bead model and that E. coli EC166 may employ an active mechanism of growth inhibition at a later stage of biofilm formation. Genomic analysis identified a type VI secretion system, including the toxic effector protein RhsD, within the E. coli EC166 genome which may be responsible for reduced Salmonella growth in the presence of E. coli EC166. Together, these results suggest that E. coli EC166 actively inhibits or kills S. Typhimurium and S. Enteritidis.

Item Type: Thesis (Masters)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 22 Mar 2022 09:29
Last Modified: 22 Mar 2022 09:29


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