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Effect of membrane lipid composition on resistance against surfactin
Pinkas, Dominik ; Seydlová, Gabriela (advisor) ; Sýkora, Jan (referee)
Surfactin is an antibiotic produced by several strains of B. subtilis. Its broad range of biological activities is interesting from perspective of medicine, food industry and bioremediation and is based on its surface-active properties and interaction with biological membranes. The latter means mainly forming ion channels, conductive pores and with increasing concentration eventually disrupting membrane structure in detergent-like manner. Mechanism of resistance of producing strain against its own toxic product is not yet fully understood. This work shows that it could be based on surfactin target modification - which means altering membrane lipid composition. We were able to recognize surfactin-formed ion channels or pores with a broad range of conductivities spanning from 2 pS to 2 nS using BLM method. Liposome leakage assay with carboxyfluorescein revealed few distinct mechanisms of lysis, differing in amplitude, rate of lysis and cooperativity. Increased content of anionic lipids with conical shape, namely cardiolipin and phosphatidic acid led to substantial increased membrane resistance to surfactin-induced permeabilization. Key words: membrane, surfactin, Bacillus subtilis, cardiolipin, black lipid membranes, liposomes
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Mechanisms of bacterial persistence and clinical significance
Smělíková, Eva ; Melter, Oto (advisor) ; Pinkas, Dominik (referee)
Persistent bacteria, shortly persisters, are cells that are characterized by their tolerance to antibiotics without containing resistance genes. These are not resistant bacteria, because resistant bacteria are determined by genetic code. Persisters are indistinguishable from other antibiotic sensitive bacteria, and they are rather transient phenotypic subpopulations. Probably all types of bacteria can create a persistent stage, the ability is not species-bound and persistence has been described in a number of bacterial species. The reason for the formation of persistence may be sudden stress, then it is induced formation, or the reason may be an insurance for the future, then we call it stochastic phenotypic variability. Then a variety of phenotypes of different subpopulations within a genetically uniform population can be distinguished. They differ in growth properties and tolerance to antibiotics. Bet-hedging strategy is a hypothesis that describes persistence as insurance against the risk of external fluctuations. During stress an alarmon guanosine tetraphosphate or guanosine pentaphosphate is accumulated to alert the cell to unfavorable conditions and it initiates transition to a more tolerant state. The existence of these tolerant subpopulations is important in recurrent diseases because small...
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Mechanisms of bacterial persistence and clinical significance
Smělíková, Eva ; Melter, Oto (advisor) ; Pinkas, Dominik (referee)
Persistent bacteria, shortly persisters, are cells that are characterized by their tolerance to antibiotics without containing resistance genes. These are not resistant bacteria, because resistant bacteria are determined by genetic code. Persisters are indistinguishable from other antibiotic sensitive bacteria, and they are rather transient phenotypic subpopulations. Probably all types of bacteria can create a persistent stage, the ability is not species-bound and persistence has been described in a number of bacterial species. The reason for the formation of persistence may be sudden stress, then it is induced formation, or the reason may be an insurance for the future, then we call it stochastic phenotypic variability. Then a variety of phenotypes of different subpopulations within a genetically uniform population can be distinguished. They differ in growth properties and tolerance to antibiotics. Bet-hedging strategy is a hypothesis that describes persistence as insurance against the risk of external fluctuations. During stress an alarmon guanosine tetraphosphate or guanosine pentaphosphate is accumulated to alert the cell to unfavorable conditions and it initiates transition to a more tolerant state. The existence of these tolerant subpopulations is important in recurrent diseases because small...
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The structure and role of type III secretion system and other virulence factors in pathogenesis of pertussis
Štipl, Daniel ; Večerek, Branislav (advisor) ; Pinkas, Dominik (referee)
Bordetella pertussis is a significant human pathogen which colonises a respiratory tract. The infection with B. pertussis results in serious and highly contagious disease called pertussis or whooping cough. B. pertussis produces wide range of virulence factors such as pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin, tracheal cytotoxin, adhesins and type III secretion system (T3SS). The BvgAS is two-component signal transduction system that provides the complex regulation of B. pertussis virulence. The virulence factor T3SS is used by some Gram-negative bacteria to colonise the host and is responsible for pathogenesis of the infection. T3SS takes a role in virulence of mammalian pathogen B. bronchiseptica, closely related to B. pertussis. The importance of T3SS in virulence of B. pertussis remains to be investigated. Significant advance in structure, function and regulation of the most of virulence factors have been accomplished in last few decades. The causative agents of pathogenesis in that infection remain unknown. Key words: Bordetella, T3SS, gene expresssion regulation, virulence factor, pathogenesis
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Mode of action of antimicrobial lipopeptides produced by Bacillus subtilis
Pinkas, Dominik ; Seydlová, Gabriela (advisor) ; Žíla, Vojtěch (referee)
Increasing bacterial resistance to classical antibiotics and emergence of multi-resistant strains impose a constant threat. Antimicrobial compounds of bacterial origin are an important source of new antibacterial therapeutic agents needed to answer this issue. Three families of lipopeptides produced by Bacillus subtilis - surfactins, fengycins and iturins represent an interesting class of such compounds. They exert a wide range of biological activities and possess a good potential for modifications and improvement of their structure and function. Lipopeptides produced by B. subtilis are surface active compounds capable of reducing surface/interface tension. The variety of their biological activities stems from their ability to insert into lipid membranes leading to disruption and permeabilization of the membrane. Specific mode of action differs between the three families but the common feature is that it is concentration dependent. First, lipopeptides induce ion leakage, pore formation and then the increasing concentration eventually causes complete solubilisation of the membrane in a detergent-like manner. In addition, surfactin can inhibit some enzymes by chelating divalent cations required for their activity. These properties make the B. subtilis lipopeptides promising compounds for commercial applications.
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Effect of membrane lipid composition on resistance against surfactin
Pinkas, Dominik ; Seydlová, Gabriela (advisor) ; Sýkora, Jan (referee)
Surfactin is an antibiotic produced by several strains of B. subtilis. Its broad range of biological activities is interesting from perspective of medicine, food industry and bioremediation and is based on its surface-active properties and interaction with biological membranes. The latter means mainly forming ion channels, conductive pores and with increasing concentration eventually disrupting membrane structure in detergent-like manner. Mechanism of resistance of producing strain against its own toxic product is not yet fully understood. This work shows that it could be based on surfactin target modification - which means altering membrane lipid composition. We were able to recognize surfactin-formed ion channels or pores with a broad range of conductivities spanning from 2 pS to 2 nS using BLM method. Liposome leakage assay with carboxyfluorescein revealed few distinct mechanisms of lysis, differing in amplitude, rate of lysis and cooperativity. Increased content of anionic lipids with conical shape, namely cardiolipin and phosphatidic acid led to substantial increased membrane resistance to surfactin-induced permeabilization. Key words: membrane, surfactin, Bacillus subtilis, cardiolipin, black lipid membranes, liposomes
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