An investigation into the expression of Streptococcus pyogenes surface proteins during growth in the biofilm state compared to the planktonic state.
Cardiff Metropolitan University
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Introduction: Streptococcus pyogenes (MGAS6180) is a Group A streptococci that can infect its host to cause a variety of diseases such as pharyngitis and necrotising fasciitis. Their virulence factors allow it to successfully adhere, colonise and invade a host's cells, whilst evading the host's immune system. Many surface proteins initiate adhesion, and AspA, Sof Spy0632 and Spy0l09 will be investigated in this study to determine and compare the differential expression in the biofilm and planktonic state. Method: MGAS6I80 biofilms were grown and optimised in uncoated micro-titre plates, which was then applied when growing large scale biofilms in Petri dishes. Planktonic cells were grown in TSB, and the OD measured to determine the mid-exponential phase of growth. The four surface protein genes, AspA, Sof, Spy0632 and Spy0109, were identified using PCR and agarose gel electrophoresis. The PCR technique was optimised for Mg2+ concentration and annealing temperatures of primers. Results: A 20% concentration of MGAS6180 in TSB was utilized in large scale biofilm growth, which revealed a significant number of viable cells. The mid-exponential phase of growth in planktonic cells was 4.5-5 hours; the optimum time for harvesting cells. All of the genes being studied were successfully identified, and the PCR reaction including all annealing temperatures was optimised. Conclusion: The genes identified encode for surface proteins that are used to adhere to the host's cells, as part of its virulence factors. It also shows that MGAS6180 produces adequate biofilms, and can survive in the planktonic state. All of these preliminary findings can be used in further investigations, to ultimately compare the expression of surface protein genes in both the planktonic and biofilm state.
BSc (Hons) Applied Biomedical Science
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