National Repository of Grey Literature 16 records found  1 - 10next  jump to record: Search took 0.03 seconds. 
Mode of action of the 4th generation of antibacterial compounds lipophosphonoxins
Helusová, Michaela ; Mikušová, Gabriela (advisor) ; Mašín, Jiří (referee)
Lipophosphonoxins are small synthetic antimicrobials targeting the cytoplasmic membrane of bacteria. This thesis focuses on comparison of three lipophosphonoxins which differ in the number of carbons in its modules and in antimicrobial and hemolytic activity. The most promising candidate compound is lipophosphonoxin 7072 showing good antimicrobial activity as well as low hemolytic activity. Other two tested lipophosphonoxins are 7070 displaying high hemolytic activity and weakly antibacterial lipophosphonoxin 7107. The pore-forming activity of lipophosphonoxins is investigated using model membranes as well as living bacteria Staphylococcus aureus and Escherichia coli. The results show that small difference in structure can fundamentally affect the activity of these molecules. Lipophosphonoxins 7072 a 7070 display equal antibacterial activity against tested bacteria by forming pores in the bacterial membrane. Bacteria rapidly die of loss of membrane potential caused by lipophosphonoxins. The high hemolytic activity of the compound 7070 is probably related with its preference for uncharged membranes. The weak antimicrobial activity of 7107 is caused by its capability to form only small pores and its incapability to overcome and disrupt the outer membrane. Key words: antimicrobial agents,...
Interaction of influenza virus with cell defence mechanisms
Vochyánová, Klára ; Drda Morávková, Alena (advisor) ; Mikušová, Gabriela (referee)
Influenza virus infection is one of the most current problems nowadays. Its unique ability to strongly inhibit cell immune response on many different levels and its pandemic potential make it a subject of interest of many research groups. The Influenza virus uses mainly NS1 protein to inhibit the immune response. NS1 protein is able, on one hand, to bind RNA and mask it against recognition by cellular sensors and other proteins. On the other hand, NS1 protein possesses a catalytic domain. Using this domain it interacts with many cellular proteins, interferes with signal transduction and guarantees successful infection. NS1 protein is one of principal pathogenicity instruments of the Influenza virus and it deserves appropriate attention.
Production of toxins by Bacillus subtilis and their roles in interspecies competitions.
Šureková, Kristína ; Krásný, Libor (advisor) ; Mikušová, Gabriela (referee)
Bacillus subtilis is a gram positive soil bacterium that is surrounded by many other microorganisms its environment. That is why it is necessary for the bacterium to be able to fight with these microorganisms for the nutrients and living space. B. subtilis contains the modules in its genetic make-up that improve its ability to compete. These modules are called the toxin-antitoxin systems. This Diploma Thesis is trying to identify yet undescribed extracellular toxins produced by the wild type BSB1 strain of B. subtilis. The related microorganism Bacillus megaterium was used as a competing bacterium. The contact-dependent or independent manner of killing the competing bacterium was demonstrated using this model. By deletion analysis and comparisons of the genomes of the various strains of B. subtilis, the SPβ prophage was first identified as a region containing an unknown toxin(s). Analysis of the extracellular proteome of B. subtilis subsequently revealed an unknown toxin (or toxin complex, respectively) of the molecular weight exceeding 100 kDa. Even more fascinating was the finding that such a large protein molecule is resistant to the pancreatic protease, trypsin. Subsequent non-enzymatic cyanogen bromide cleavage of the extracellular proteins and their analysis by mass spectrometry revealed...
Mode of action and nature of different susceptibility of bacteria to antibacterial compounds lipophosphonoxins
Havlová, Noemi ; Mikušová, Gabriela (advisor) ; Krásný, Libor (referee)
Lipophosphonoxins (LPPO) are small synthetic antibacterial compounds targeting the cytoplasmic membrane. 1st generation of LPPO (LPPO I) displays an antimicrobial activity against Gram positive bacteria, however they do not show any activity against Gram negatives. After the modification of the iminosugar module (bearing the positive charge) the 2nd generation of LPPO (LPPO II) were synthetized. LPPO II exhibit broadened activity against Gram positive bacteria and also kill Gram negatives, including multiresistant strains. This work focuses on the mode of action of LPPO - the pore-forming activity of these substances is investigated on model membranes as well as in vivo. It also deals with the nature of different activity against Gram positive and Gram negative bacteria using model bacteria Bacillus subtilis and Escherichia coli. The results show that the insensitivity of Gram negative bacteria against LPPO I is probably caused by the different cell wall structure and the presence of the outer membrane that LPPO are almost unable to overcome. Also, the composition of phospholipids in the target membrane influences the antimicrobial activity of LPPO. Higher proportion of phospholipids with neutral charge reduces the LPPO pore-forming activity but is also responsible for low cytotoxicity in...
Membrane fluidization by alcohols inhibits DesK-DesR signalling in Bacillus subtilis
Vaňousová, Kateřina ; Mikušová, Gabriela (referee)
After cold shock, the Bacillus subtilis desaturase Des introduces double bonds into the fatty acids of existing membrane phospholipids. The synthesis of Des is regulated exclusively by the two-component system DesK/DesR; DesK serves as a sensor of the state of the membrane and triggers Des synthesis after a decrease in membrane fluidity. The aim of our work is to investigate the biophysical changes in the membrane that are able to affect the DesK signalling state. Using linear alcohols (ethanol, propanol, butanol, hexanol, octanol) and benzyl alcohol, we were able to suppress Des synthesis after a temperature downshift. The changes in the biophysical properties of the membrane caused by alcohol addition were followed using membrane fluorescent probes and differential scanning calorimetry. We found that the membrane fluidization induced by alcohols was reflected in an increased hydration at the lipid-water interface. This is associated with a decrease in DesK activity. The addition of alcohol mimics a temperature increase, which can be measured isothermically by fluorescence anisotropy. The effect of alcohols on the membrane periphery is in line with the concept of the mechanism by which two hydrophilic motifs located at opposite ends of the transmembrane region of DesK, which work as a molecular...
Characterization of the ABC-F protein Sco0636 in Streptomyces coelicolor
Pinďáková, Nikola ; Balíková Novotná, Gabriela (advisor) ; Mikušová, Gabriela (referee)
The main topic of this diploma thesis is ARE (resistance) proteins from the ABC-F family of the second class of ABC proteins. ARE proteins confer resistance to antibiotics that bind to a large ribosomal subunit and therefore inhibit proteosynthesis. One of the ARE proteins is the Lmr (C) protein, which is part of the linkomycin biosynthesis cluster of Streptomyces lincolnensis, and according to new results, Lmr (C) does not have to be just resistant protein but may have also regulatory function. We decided to study Sco0636, the closest homologue to Lmr (C) in Streptomyces coelicolor, which is a model organism in the study of secondary metabolism. Thanks to the production of color pigments, it is possible to monitor the effect of ARE proteins on secondary metabolism directly on the plates. I prepared the deletion mutant and the strain with constitutive expression of sco0636, and observed the effect on the phenotype. I followed the production of a blue asset and set a minimum inhibitory concentration to selected antibiotics, which bind to the ribosome. I have found that Sco0636 gives high resistance to tiamulin and so it has been named TiaA. The deletion of gene sco0636 accelerated production of actinorodine, and constitutive expression of this gene slowed down production. Keywords: ABC proteins,...
Mode of action of the 4th generation of antibacterial compounds lipophosphonoxins
Helusová, Michaela ; Mikušová, Gabriela (advisor) ; Mašín, Jiří (referee)
Lipophosphonoxins are small synthetic antimicrobials targeting the cytoplasmic membrane of bacteria. This thesis focuses on comparison of three lipophosphonoxins which differ in the number of carbons in its modules and in antimicrobial and hemolytic activity. The most promising candidate compound is lipophosphonoxin 7072 showing good antimicrobial activity as well as low hemolytic activity. Other two tested lipophosphonoxins are 7070 displaying high hemolytic activity and weakly antibacterial lipophosphonoxin 7107. The pore-forming activity of lipophosphonoxins is investigated using model membranes as well as living bacteria Staphylococcus aureus and Escherichia coli. The results show that small difference in structure can fundamentally affect the activity of these molecules. Lipophosphonoxins 7072 a 7070 display equal antibacterial activity against tested bacteria by forming pores in the bacterial membrane. Bacteria rapidly die of loss of membrane potential caused by lipophosphonoxins. The high hemolytic activity of the compound 7070 is probably related with its preference for uncharged membranes. The weak antimicrobial activity of 7107 is caused by its capability to form only small pores and its incapability to overcome and disrupt the outer membrane. Key words: antimicrobial agents,...
Characterization of microorganisms with biodegradation potential for sulfonamides
Sedláček, Jan ; Palyzová, Andrea (advisor) ; Mikušová, Gabriela (referee)
Sulfonamides are antibiotics that are frequently used both in human and veterinary medicine. The combinations of abundant use of these antibiotics and their natural resistance to decay leads often to long term persistence in the environment. This accumulation, especially in living organisms, may lead to subsequent toxicosis. Also, presence of these antibiotic in nature poses problems with regard to the spread of genes for antibiotic resistance between potential pathogens. These facts led to an increase interest in studying the sulfonamide biodegradation and subsequent sulfonamide removal from the environment. In this work it was possible to isolate and characterize the microorganism Acinetobacter sp. strain 49. This microorganism was able to biodegrade under right conditions sulfamethoxazole with 80 % efficiency. Sulfamethoxazole is one of the most commonly found sulfonamide in the nature.
Functional membrane microdomains in the bacterial cytoplasmic membrane
Švecová, Magdaléna ; Mikušová, Gabriela (advisor) ; Koukalová, Alena (referee)
Functional membrane microdomains are structural heterogeneities in bacterial cytoplasmic membrane with up to few tens of nanometers in size. Same as in the case of eukaryotic lipid rafts the lipid and protein composition and fluidity of bacterial membrane microdomains differ from the rest of the membrane. Membrane microdomains contain the structural analogues of eukaryotic flotilin as well as hopanoids and carotenoids as functional analogues of cholesterol in eukaryotic lipid rafts. In functional membrane microdomains there are located proteins associated with membrane trafficking, signaling, secretion, biofilm formation, and sporulation. Functional membrane microdomains are specific sites for the entry of certain antibiotics into cells. What is more, disassembly of functional membrane microdomains might be regarded as a possible novel mechanism of bacterial infections suppression that is caused by antibiotic resistant bacterial pathogens. In the absence of membrane domains proteins which require for their functions the membrane domain localization lose their activity. This may result in inhibition of bacterial cell growth. Key words: Functional membrane microdomains, bacterial cytoplasmic membrane, cardiolipin, hopanoids, flotilins, antibiotic resistance
Membrane fluidization by alcohols inhibits DesK-DesR signalling in Bacillus subtilis
Vaňousová, Kateřina ; Mikušová, Gabriela (referee)
After cold shock, the Bacillus subtilis desaturase Des introduces double bonds into the fatty acids of existing membrane phospholipids. The synthesis of Des is regulated exclusively by the two-component system DesK/DesR; DesK serves as a sensor of the state of the membrane and triggers Des synthesis after a decrease in membrane fluidity. The aim of our work is to investigate the biophysical changes in the membrane that are able to affect the DesK signalling state. Using linear alcohols (ethanol, propanol, butanol, hexanol, octanol) and benzyl alcohol, we were able to suppress Des synthesis after a temperature downshift. The changes in the biophysical properties of the membrane caused by alcohol addition were followed using membrane fluorescent probes and differential scanning calorimetry. We found that the membrane fluidization induced by alcohols was reflected in an increased hydration at the lipid-water interface. This is associated with a decrease in DesK activity. The addition of alcohol mimics a temperature increase, which can be measured isothermically by fluorescence anisotropy. The effect of alcohols on the membrane periphery is in line with the concept of the mechanism by which two hydrophilic motifs located at opposite ends of the transmembrane region of DesK, which work as a molecular...

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