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Influence of environment in host cells on heterogeneity of virulence factors expression in Salmonella
Mathéová, Paulína ; Černý, Ondřej (advisor) ; Konopásek, Ivo (referee)
Bacteria of the genus Salmonella are one of the most important human pathogens. Salmonella expresses several virulence factors, including the type three secretion system encoded on the Salmonella pathogenicity island 2 (SPI-2 T3SS) and its effector proteins. SPI- 2 T3SS effector proteins allow the bacteria to colonize host cells, persist there and use them as a Trojan horse for migration throughout the host organism. Although the function of the SPI- 2 T3SS is essential for the bacterial population during systemic infection, some bacteria do not express this virulence factor and benefit from its expression by other members of the population. Similar heterogeneity in expression of other virulence factors has been shown to be crucial for their function. This work focuses on the heterogeneity of expression of selected SPI-2 T3SS effector proteins under the influence of host factors (pH, ROS, RNS) affecting bacteria during intracellular infection of macrophages. Using a fluorescent reporter system suitable for flow cytometry the expression of selected effector proteins was detected at the level of individual bacteria. The obtained data show, that individual bacteria respond differently to the decrease in pH in their vicinity. Part of the bacterial population starts to express the studied effector...
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Heterogeneity of expression of virulence factors of Salmonella.
Mathéová, Paulína ; Černý, Ondřej (advisor) ; Lichá, Irena (referee)
The emergence of phenotypically heterogeneous individuals within an isogenic bacterial population is considered to be an important adaptation to the host environment. It allows survival of some bacterial subpopulations under diverse stress conditions caused by the host immune system, the emergence of a "division of labor" and cooperation between individual bacteria. Bacteria of the genus Salmonella are important pathogens in humans and livestock. Many of the key virulence factors of Salmonella are heterogeneously expressed. The phenotypic diversity of individual bacteria allows certain individuals to escape the host's immune system and ensure that the gene pool is preserved to future generations. In case when change in conditions causes complete extinction of part of the Salmonella population from the environment, the remaining individuals are able to restore the size of the population and phenotypic diversity, after overcoming unfavourable conditions. This work summarises the knowledge about heterogeneity of expression of virulence factors of Salmonella and the characteristics of individual subpopulations in different environmental conditions. Keywords: Salmonella, heterogeneity, virulence factors, bet-hedging, division-of-labor, bacterial subpopulations.
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