D'Angelo, Caterina (2024) Biofilm of polar marine bacteria as a biotechnological tool. [Tesi di dottorato]

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Biofilms, the prevalent form of life on Earth, are a multicellular aggregates embedded in a self-produced extracellular matrix. This microbial way of life impacts human healthcare due to the high antibiotic resistance typical of the microorganisms in biofilm. Therefore, the necessity of innovative and effective antibiofilm therapy is becoming urgent. While biofilms can be problematic in medical fields, there is growing interest in utilizing their resistance and cooperative behaviours for beneficial applications in biotechnology. In this context, the first part of my Ph.D. project was focused on the identification of novel antibiofilm agents from Antarctic marine bacteria mainly active against Staphylococcus epidermidis, one of the most pathogen associated with indwelling medical-device infections. Specifically, I conducted a study on three different Polar marine bacteria: Psychrobacter sp. TAE2020, Pseudomonas sp.TAE6080 and Pseudoalteromonas haloplanktis TAD2020. In the case of Psychrobacter sp. TAE2020, a high-mass complex of proteins and polysaccharides named CATASAN was discovered and purified. CATASAN demonstrated the ability to interfere with all the phases of S. epidermidis biofilm and also exhibited emulsification activity. Additionally, it was found that this bacterium produced a low molecular compound/s with surfactant and antibiofilm capabilities, the molecule involved in these activities appears to be a lipopeptide. For Pseudomonas sp. TAE6080, a novel periplasmatic protein, similar to Pseudomonas aeruginosa PAO1 azurin, named cold-azurin was discovered. Cold-azurin exhibited both anti-adhesive and antibiofilm capability. The protein was recombinantly produced in E. coli and purified. Concerning Pseudoalteromonas haloplanktis TAD2020 it turned out that the bacterium secreted small-organic antibiofilm compound/s and that the different growth conditions have a deep influence on the bioactive compound production. However, the complexity of the active samples hindered for now the antibiofilm/s identification. In the second part of my work, I explored the use of Pseudoalteromonas haloplanktis TAC125 biofilm as a non-conventional platform for recombinant proteins production. After demonstrating the feasibility of this innovative system and optimizing the production process conditions, an ad-hoc expression vector suitable for biofilm growth was set up.

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