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Role of extracellular DNA in microbial biofilms
Gromov, Anton ; Chytilová, Aneta (referee) ; Obruča, Stanislav (advisor)
Abstract This bachelor’s thesis deals with defining the role of extracellular DNA in microbial biofilms. The thesis includes a part about the basic characteristics and functions of biofilms, as well as the characteristics and functions of extracellular DNA. The theoretic part additionally deals with the process of formation of biofilms, and the influence of different types of stresses on it. Also, the paper discusses the role of such stresses. The role of biofilm in bacteria and their reproduction methods are also discussed. An interesting section of the thesis outlines the impact of antibiotics on biofilms, or the ways to gain DNA or use DNase. The eDNA functions and their effects on bacterial defence will be discussed thoroughly. In the experimental part, the biofilm content was examined and compared with cells growing in a liquid and solid medium. Measurement of DNA content in media was carried out and the effects of salt and temperature stresses on biofilm were also measured. Stress conditions affected the production of PHB, which is used as a reserve form of energy and carbon. Total sugars were measured using an anthracite reagent to study the effects of stresses on the content of macromolecules. The presence of eDNA in biofilms and planktonic cells was firstly checked using gel electrophoresis and then accurate concentrations in planktonic and biofilm cells were determined using different spectrophotometric methods.
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Influence of Staphylococcus aureus Quorum sensing system to antibiotic tolerance
Šaňková, Michaela ; Lichá, Irena (advisor) ; Buriánková, Karolina (referee)
Staphylococcus aureus is a gram-positive opportunistic pathogenic bacterium that causes a range of chronic infections especially to weakened individuals. Recently, the most serious problem in clinical medicine has been infections caused by so-called persisters. They form a subpopulation of cells that, thanks to adaptations to stressful conditions, are able to withstand lethal doses of antibiotics and then cause an infection again. Agr system, which is responsible for the mechanism of quorum-sensing, plays the main role in switching between the active virulent form and the persistent form associated with biofilm formation. During chronic infections, adaptive mutations accumulate in this Agr system and affect the ability to persist. For the purpose of this thesis, clinical isolates were obtained from patients diagnosed with cystic fibrosis in chronological order within the first three years of their lives. The aim of this thesis was to confirm the influence of adaptive mutations on the persistence ability of clinical isolates and also to observe how the membrane potential and metabolic activity change depending on the on the action of selected antibiotics. Additional aim was to create a deletion of the response regulator AgrA gene using the CRISPR/Cas9 system. In order to characterize the persistence...
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Biofilm formation in Streptococcus pneumoniae
Jarošová, Václava ; Petráčková, Denisa (advisor) ; Matyska Lišková, Petra (referee)
Biofilm is a structured community of cells adhered to the surface or to each other and surrounded by extracellular matrix. Biofilm is fomed in several steps starting from single cells adhered to the surface up to microcolonies linked by channels. Because of a higher resistance to antibiotics the current hot topics in the biofilm research are formation of biofilms on medical materials and treatment of bacterial infections associated with biofilms. This work is focused on a biofilm forming bacteria Streptococcus pneumoniae. It is a potentially pathogenic bacterium which colonizes the upper respiratory tract and causes a number of diseases. Biofilms formed by S. pneumoniae exhibit increased resistance to antibiotics, therefore, alternative antimicrobial agents have been recently studied. For biofilm formation studies both open and closed systems are used. The flow cell and biofilm reactors represent commonly used open systems. Closed cultivation systems are for example a Calgary biofilm device and a micro titer plate-system developed by Christensen et al.
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Role of small effector molecules in bacterial signalling.
Kolář, Petr ; Lichá, Irena (advisor) ; Hilská, Markéta (referee)
Small effector molecules play an important role in bacterial physiology. There are many types of them in the bacterial cell. One group are small signalling molecules which participate in quorum sensing, enabling bacterial cell-cell communication as part of a extracellular signalling. These molecules mediate information about the cell density and different qualities of the extracellular matrix. Next group of small effector molecules are modified nucleotides. They participate in intracellular signalling pathways which regulate the switch of bacterial lifestyle according to changing environment. Best studied are signalling pathways using the molecules - c-di-GMP and (p)ppGpp. Detail studies were done in case of gram positive (Bacillus subtilis) and gram negative (Escherichia coli, Vibrio cholerae) bacteria, where was proved the connection between c-di-GMP signalling pathways and quorum sensing (Vibrio cholerae, Xanthomonas campestris). Important discovery in field of small effector molecules is the c-di-AMP signalling pathway in Bacillus subtilis. New regulatory mechanisms were determined in well-known small effector molecule cAMP, regarding the signalling pathways connections (Vibrio cholerae). Recent studies considering the cooperation of the extracellular and intracellular signalization pathways...
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Chemical signaling among microorganisms
Karásek, Filip ; Palková, Zdena (advisor) ; Převorovský, Martin (referee)
The work summarizes the knowledge about chemical communication among microorganisms, focusing mainly on the quorum sensing phenomenon, but briefly discussing also other molecules with signaling function. The work presents fundamental information on quorum sensing and some other signaling molecules in selected grampositive and gramnegative bacteria and in yeast. It also describes an universal system of communication among different bacteria and briefly mentions communication between bacteria and yeast. Key words: Quorum sesnig, signal molecule, signal pathway, bacteria, yeast, communication
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Molecular mechanisms of virulence regulation in Staphylococcus aureus
Kekrt, Lukáš ; Tkadlec, Jan (advisor) ; Botka, Tibor (referee)
Staphylococcus aureus is one of the most common causes of bacterial infection in human. The bacterium is equipped by the broad spectrum of virulence factors, including modulators of immune response and also invasion factors able to destroy human cells and tissues. S. aureus is also able to asymptomatically colonize healthy individuals. Precise regulation of virulence factor expression is crucial for S. aureus survival. The aim of this thesis is to describe in detail molecular mechanisms regulating S. aureus virulence factor expression. Among these mechanisms belongs quorum sensing dependent agr system, sigma B general stress response, Sar family of transcription factors and metabolism- dependent regulators CodY and CcpA. Keywords: S. aureus, virulence, quorum sensing, agr systém, sar, sigma B, CodY, alpha-hemolysin.
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Biofilm formation in Streptococcus pneumoniae
Jarošová, Václava ; Petráčková, Denisa (advisor) ; Matyska Lišková, Petra (referee)
Biofilm is a structured community of cells adhered to the surface or to each other and surrounded by extracellular matrix. Biofilm is fomed in several steps starting from single cells adhered to the surface up to microcolonies linked by channels. Because of a higher resistance to antibiotics the current hot topics in the biofilm research are formation of biofilms on medical materials and treatment of bacterial infections associated with biofilms. This work is focused on a biofilm forming bacteria Streptococcus pneumoniae. It is a potentially pathogenic bacterium which colonizes the upper respiratory tract and causes a number of diseases. Biofilms formed by S. pneumoniae exhibit increased resistance to antibiotics, therefore, alternative antimicrobial agents have been recently studied. For biofilm formation studies both open and closed systems are used. The flow cell and biofilm reactors represent commonly used open systems. Closed cultivation systems are for example a Calgary biofilm device and a micro titer plate-system developed by Christensen et al.
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Role of small effector molecules in bacterial signalling.
Kolář, Petr ; Lichá, Irena (advisor) ; Hilská, Markéta (referee)
Small effector molecules play an important role in bacterial physiology. There are many types of them in the bacterial cell. One group are small signalling molecules which participate in quorum sensing, enabling bacterial cell-cell communication as part of a extracellular signalling. These molecules mediate information about the cell density and different qualities of the extracellular matrix. Next group of small effector molecules are modified nucleotides. They participate in intracellular signalling pathways which regulate the switch of bacterial lifestyle according to changing environment. Best studied are signalling pathways using the molecules - c-di-GMP and (p)ppGpp. Detail studies were done in case of gram positive (Bacillus subtilis) and gram negative (Escherichia coli, Vibrio cholerae) bacteria, where was proved the connection between c-di-GMP signalling pathways and quorum sensing (Vibrio cholerae, Xanthomonas campestris). Important discovery in field of small effector molecules is the c-di-AMP signalling pathway in Bacillus subtilis. New regulatory mechanisms were determined in well-known small effector molecule cAMP, regarding the signalling pathways connections (Vibrio cholerae). Recent studies considering the cooperation of the extracellular and intracellular signalization pathways...
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Role of extracellular DNA in microbial biofilms
Gromov, Anton ; Chytilová, Aneta (referee) ; Obruča, Stanislav (advisor)
Abstract This bachelor’s thesis deals with defining the role of extracellular DNA in microbial biofilms. The thesis includes a part about the basic characteristics and functions of biofilms, as well as the characteristics and functions of extracellular DNA. The theoretic part additionally deals with the process of formation of biofilms, and the influence of different types of stresses on it. Also, the paper discusses the role of such stresses. The role of biofilm in bacteria and their reproduction methods are also discussed. An interesting section of the thesis outlines the impact of antibiotics on biofilms, or the ways to gain DNA or use DNase. The eDNA functions and their effects on bacterial defence will be discussed thoroughly. In the experimental part, the biofilm content was examined and compared with cells growing in a liquid and solid medium. Measurement of DNA content in media was carried out and the effects of salt and temperature stresses on biofilm were also measured. Stress conditions affected the production of PHB, which is used as a reserve form of energy and carbon. Total sugars were measured using an anthracite reagent to study the effects of stresses on the content of macromolecules. The presence of eDNA in biofilms and planktonic cells was firstly checked using gel electrophoresis and then accurate concentrations in planktonic and biofilm cells were determined using different spectrophotometric methods.
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