1,721,034 research outputs found
Interactions of cell division protein FtsZ with large and small molecules
Full text linkBacteria are one of the most important microorganisms in biotechnology and in our life. They play many good roles for humans, e.g. by breaking down food and producing certain vitamins and nutrients in the human gastrointestinal tract. However, a small number of bacteria, called pathogens, may also cause serious infections and diseases. These bacteria are extensively studied for centuries in order to better understand their internal mechanisms. The knowledge gained from these studies is used to search for weak points in bacteria, which can be targeted by popular drugs called antibiotics. The weak points in bacteria are mechanisms that are essential for viability or normal function, and, when blocked, completely inactivate the whole bacterial organism. These mechanisms include among others: essential protein biosynthesis pathways, synthesis of the bacterial cell wall, and cell division, the mechanism that allows bacteria to proliferate. In our work we tried to better understand the cell division process in two bacterial species, Bacillus subtilis and Escherichia coli. To this end we used essential protein FtsZ, which is the key player of cell division. In our work we studied FtsZ alone; in the presence of other proteins that directly interact with FtsZ; and in the presence of small molecules, which could potentially block FtsZ and bacterial cell division, thus act as antibacterial agents. The work described in my thesis enhances our knowledge of bacterial cell division and contributes to research in antibiotic development
Let op! Cell wall under construction: Untangling Bacillus subtilis cell wall synthesis
Full text linkDe vorm van een bacteriële cel wordt bepaald door een celwand die bestaat uit peptidoglycaan (PG). Om PG te synthetiseren is het nodig dat zijn bouwsteen (Lipid II) in het cytoplasma wordt gesynthetiseerd, deze kan dan over het membraan klappen en door penicilline bindende eiwitten (PBP’s) ingebouwd worden in de celwand. De studie van celwand synthese helpt bij het begrijpen van de toenemende bacteriële resistentie tegen bestaande antibiotica en bij het ontwikkelen van nieuwe antibiotica. In dit proefschrift worden drie verschillende onderzoekslijnen beschreven, waarbij de grampositieve, staafvormige Bacillus subtilis is gebruikt als modelorganisme. Als eerste werd de werking van nisine, een lantibiotica dat gaten in de membraan maakt en Lipid II clustert, onderzocht. Onze resultaten laten zien dat deze processen altijd samen gaan. Ten tweede werden de chemische verschillen in de opbouw van de celwand bestudeerd. We hebben laten zien dat de samenstelling van de celwand op de plek waar de bacterie zich deelt, verschilt van de rest van de celwand. De delingsplek is verrijkt met peptidoglycaan dat minder bewerkingen heeft ondergaan. Tot slot werd de functie van de PBP2B PASTA domeinen geanalyseerd. Wij hebben laten zien dat, hoewel t de PASTA domeinen niet nodig zijn voor de lokalisatie van PBP2B, ze wel een rol spelen in celdeling, waarschijnlijk door een interactie met het celdelingseiwit DivIB
Functional role of lipids in bacterial protein translocation
Full text linkAbout 30% of proteins synthesized in the cytosol of bacteria perform their function outside of the cell and either have to be inserted into or translocated across the cytoplasmic membrane. The system responsible for protein translocation is the Secretory (Sec) pathway, that in its minimal form consists of the protein-conducting membrane embedded channel SecYEG and the motor protein SecA. Since the Sec pathway mostly comprises of membrane proteins, studies on this system are usually done with detergent extracted proteins. However, detergents may alter structural and functional properties of proteins. We have reconstituted the protein-conducting SecYEG channel into model membranes, i.e., small nanodiscs and supported lipid bilayers, to investigate functional and mechanistic aspects of the Sec translocon in a physiologically relevant environment. This work revealed that the phospholipids of the cytoplasmic membrane do not only act as a supportive matrix for protein translocation, but that anionic phospholipids promote the functional interaction between SecYEG and SecA. Furthermore, computational studies show that anionic phospholipids localize near to the lateral gate of SecYEG, where they may facilitate the initiation of protein translocation through promoting the folding of the signal sequences of secretory proteins
Developing a tool set to investigate antimicrobial mode of action in a phytopathogen
Full text linkBacteria are the most ubiquitous organisms on Earth. In a human body, there are more bacterial than human cells. Bacteria are an essential part of the carbon and nitrogen cycles which make life on Earth possible. The metabolic diversity of bacteria has been harnessed for the synthesis of industrial compounds such as pharmaceuticals, food ingredients and additives, and biocatalysts. However, a small proportion of bacteria are pathogenic, causing harm to humans and agriculture. To combat these bacteria, humans have developed antibiotics and antimicrobials, which drastically reduced mortality from bacterial diseases, increased human life expectancy worldwide, and increased the yield of food production. The widespread use of antimicrobials stimulated bacterial resistance, which has rapidly become a threat to public health and agriculture. The continued discovery of new antimicrobials is needed to avoid a widespread pandemic of antibiotic resistant bacteria and to combat plant diseases more effectively. Once discovered, antimicrobial substances can be chemically modified to improve potency, stability, delivery, or pharmacokinetics. In this thesis we investigated the mode of action of the gold liganded antimicrobial compound 7b-BF4 in the model bacterial organism Bacillus subtilis. We also studied the antimicrobial effect of chalcones BC1 and T9A in B. subtilis as well as in the citrus-infecting bacteria Xanthomonas citri. In studying the mode of action of those substances we have developed techniques that revealed new insights into the cell biology of X. citri that can be used for further studies
Mechanisms of weak acid and sugar tolerance in Saccharomyces cerevisiae
Full text linkSaccharomyces cerevisiae, commonly used as a cell factory, is capable of producing bio-based ethanol and other valuable chemical building blocks by utilizing lignocellulosic biomass as the feedstock. Complex hydrolysates of lignocellulosic biomass after pretreatments contain various hexose and pentose sugars as well as inhibitors such as acetic acid and heterocyclic organic compounds. These inhibitors impede cell growth and reduce the fermentation efficiency. This thesis focuses on the tolerance mechanisms of S. cerevisiae towards weak acids such as acetic acid and propionic acid, but also explores sugar tolerance in a xylose-fermenting specialist S. cerevisiae strain. The tolerance to weak acids is associated with intracellular acid efflux, ROS accumulation, and mitochondria functions. The observations of growth inhibitions on high xylose concentrations and maltose addition challenge the strategy of a consortium of specialists to ferment complex sugar mixtures, which inhibitions could be mitigated by controlled expression of XKS1 gene to reduce ATP consumption on high xylose concentrations and be avoided by maltose transporter deletion to eliminate of maltose influx
Dynamic localization of penicillin-binding proteins during spore development in Bacillus subtilis
No full textDuring Bacillus subtilis spore formation, many membrane proteins that function in spore development localize to the prespore septum and, subsequently, to the outer prespore membrane. Recently, it was shown that the cell-division-specific penicillin-binding proteins (PBPs) 1 and 2b localize to the asymmetric prespore septum. Here, the author studied the localization of other PBPs, fused to green fluorescent protein (GFP), during spore formation. Fusions to PBPs 4, 2c, 2d, 2a, 3, H, 4b, 5, 4a, 4* and X were expressed during vegetative growth, and their localization was monitored during sporulation. Of these PBPs, 2c, 2d, 4b and 4* have been implicated as having a function in sporulation. It was found that PBP2c, 2d and X changed their localization, while the other PBPs tested were not affected. The putative endopeptidase PbpX appears to spiral out in a pattern that resembles FtsZ redistribution during sporulation, but a pbpX knockout strain had no distinguishable phenotype. PBP2c and 2d localize to the prespore septum and follow the membrane during engulfment, and so are redistributed to the prespore membrane. A similar pattern was observed when GFP–PBP2c was expressed in the mother cell from a sporulation-specific promoter. This work shows that various PBPs known to function during sporulation are redistributed from the cytoplasmic membrane to the prespore.
Come out and play: Exploring bacterial cell wall synthesis and cell division
Full text linkBacteriën zijn eencellige organismen die over de hele wereld zijn verspreid. Normaal gesproken neemt de celgrootte van de bacterie toe voordat de bacteriecel opsplitst in twee identieke cellen. Voor deze bacteriële levenscyclus zijn twee verschillende, maar gerelateerde cellulaire processen nodig: de synthese en de deling van de celwand. Het celwandsynthese proces is erg belangrijk om er voor te zorgen dat de celwand goed gesynthetiseerd en georganiseerd wordt, aangezien het betrokken is bij de uiteindelijk grens en vorm van de bacterie. De synthese van de nieuwe celwand heeft verschillende eiwitten nodig die samenwerken om peptidoglycaan te maken, de belangrijkste component voor de celwand. Celwandsynthese is niet alleen nodig om de cel te laten groeien, maar ook om de cel zich goed te laten delen zonder dat de celwand breekt. Ook bij celdeling werken veel verschillende eiwitten samen, zodat uiteindelijk de cel gedeeld wordt in twee dochtercellen. Zowel de celwandsynthese als de celdeling zijn uitermate belangrijk en om die reden uitgebreid bestudeerd in de afgelopen decennia. Echter veel specifieke details zijn nog onbekend. Daarom wordt er in dit proefschrift een aantal verschillende manieren gebruikt om de complexiteit van de celwandsynthese en celdeling verder te ontrafelen. Verschillende aspecten zijn hierbij onderzocht: zowel de interne membraanorganisatie, als de chaperonne activiteit van het eiwit YidC en het antibacteriële effect van alkylgallaten. Deze studie onderstreept daarmee de nauw verweven relatie tussen de bacteriële celwandsynthese en de celdeling
Polymerization of the bacterial cell division protein FtsZ
Full text linkHet delen van cellen ligt ten grondslag aan de meest fundamentele processen in de natuur: groei en ontwikkeling. Het belang van een goed geregelde celdeling blijkt wel uit het feit dat alle levende organismen, van de kleinste bacterie tot de grootste boom, beschikken over een protocol voor de deling van hun cel(len). Waar een cel zich deelt, wanneer een cel zich deelt, hoe een cel zich deelt, dit alles staat onder strenge controle van de cel zelf (en soms ook nog onder controle van andere cellen in een organisme)A. ls er iets met die controle misgaat kunnen er de vreselijkste dingen gebeuren. Kanker is bijvoorbeeld een ziekte die het gevolg is van een ongebreideld delen van cellen die de controle over zichzelf kwijt zijn. Celdeling is dan ook altijd een belangrijk onderzoeksgebied van biologen geweest. Dit proefschrift gaat over een onderdeel van de celdeling in bacteriën. Bacteriën zijn (een enkele uitzondering daargelaten) eencellige organismen, en daarom bijzonder geschikt voor het bestuderen van celdeling. ...
Zie: Samenvatting
The effect of MinC on FtsZ polymerization is pH dependent and can be counteracted by ZapA
Full text linkThe min system prevents polar cell division in bacteria. Here, the biochemical characterization of the interaction of MinC and FtsZ from a Gram-positive bacterium, Bacillus subtilis, is reported. B. subtilis MinC inhibits FtsZ polymerization in a pH-dependent manner by preventing the formation of lateral associations between filaments. The inhibitory effect of MinC on FtsZ polymerization is counteracted by the presence of ZapA, a protein that promotes FtsZ filament bundling.
Rational design of berberine-based FtsZ inhibitors with broad-spectrum antibacterial activity
Full text link2013-2014 > Academic research: refereed > Publication in refereed journal201809_a bcmaVersion of RecordPublishedC
- …
