In the master's thesis, we studied the influence of the protease activity of the bacteria Pseudomonas on the survival and growth of four selected food-borne pathogenic bacteria – Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Typhimurium and Campylobacter jejuni. We determined the protease activity of selected Pseudomonas strains and demonstrated the presence or absence of the aprX gene. We found that protease activity highly depends on the selected Pseudomonas strain, medium and temperature. With the type strain Pseudomonas fragi DSM 3456 we confirmed the growth in prepared food models - soluble muscle extracts and food homogenates. For further work, we chose the Pseudomonas lundensis PD15 isolate due to its highest protease activity in the chicken meat homogenate at 15 °C. The selected pathogenic bacteria were co-cultivated with the PD15 strain and cultivated in the spent chicken meat homogenate, where the PD15 strain was previously grown. Growth of PD15 strain in chicken meat homogenate did not affect the growth of bacteria L. monocytogenes, but had an inhibitory effect on the growth of S. aureus. In spent chicken meat homogenate, the growth of planktonic cells of bacteria S. Typhimurium at 37 °C and bacteria C. jejuni at 42 °C in a microaerophilic atmosphere was improved. The influence of protease activity was confirmed by the cultivation of these two pathogenic bacteria in the spent chicken meat homogenates of different Pseudomonas strains. Increased concentrations of amino acids cysteine, methionine, glutamine and tryptophan were found in the used media, where the protease activity was high. Their presence most likely increased the growth of bacteria C. jejuni and S. Typhimurium.
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