TY - JOUR A1 - Raatz, Michael A1 - Hintsche, Marius A1 - Bahrs, Marco A1 - Theves, Matthias A1 - Beta, Carsten T1 - Swimming patterns of a polarly flagellated bacterium in environments of increasing complexity JF - European physical journal special topics N2 - The natural habitat of many bacterial swimmers is dominated by interfaces and narrow interstitial spacings where they frequently interact with the fluid boundaries in their vicinity. To quantify these interactions, we investigated the swimming behavior of the soil bacterium Pseudomonas putida in a variety of confined environments. Using microfluidic techniques, we fabricated structured microchannels with different configurations of cylindrical obstacles. In these environments, we analyzed the swimming trajectories for different obstacle densities and arrangements. Although the overall swimming pattern remained similar to movement in the bulk fluid, we observed a change in the turning angle distribution that could be attributed to collisions with the cylindrical obstacles. Furthermore, a comparison of the mean run length of the bacteria to the mean free path of a billiard particle in the same geometry indicated that, inside a densely packed environment, the trajectories of the bacterial swimmers are efficiently guided along the open spacings. Y1 - 2015 U6 - https://doi.org/10.1140/epjst/e2015-02454-3 SN - 1951-6355 SN - 1951-6401 VL - 224 IS - 7 SP - 1185 EP - 1198 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Stange, Maike A1 - Hintsche, Marius A1 - Sachse, Kirsten A1 - Gerhardt, Matthias A1 - Valleriani, Angelo A1 - Beta, Carsten T1 - Analyzing the spatial positioning of nuclei in polynuclear giant cells JF - Journal of Physics D: Applied Physics N2 - How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug. KW - Dictyostelium KW - cell nucleus KW - positioning KW - imaging KW - spatial poisson distribution Y1 - 2017 U6 - https://doi.org/10.1088/1361-6463/aa8da0 SN - 0022-3727 SN - 1361-6463 VL - 50 IS - 46 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hintsche, Marius A1 - Waljor, Veronika A1 - Grossmann, Robert A1 - Kühn, Marco J. A1 - Thormann, Kai M. A1 - Peruani, Fernando A1 - Beta, Carsten T1 - A polar bundle of flagella can drive bacterial swimming by pushing, pulling, or coiling around the cell body JF - Scientific reports N2 - Bacteria swim in sequences of straight runs that are interrupted by turning events. They drive their swimming locomotion with the help of rotating helical flagella. Depending on the number of flagella and their arrangement across the cell body, different run-and-turn patterns can be observed. Here, we present fluorescence microscopy recordings showing that cells of the soil bacterium Pseudomonas putida that are decorated with a polar tuft of helical flagella, can alternate between two distinct swimming patterns. On the one hand, they can undergo a classical push-pull-push cycle that is well known from monopolarly flagellated bacteria but has not been reported for species with a polar bundle of multiple flagella. Alternatively, upon leaving the pulling mode, they can enter a third slow swimming phase, where they propel themselves with their helical bundle wrapped around the cell body. A theoretical estimate based on a random-walk model shows that the spreading of a population of swimmers is strongly enhanced when cycling through a sequence of pushing, pulling, and wrapped flagellar configurations as compared to the simple push-pull-push pattern. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-16428-9 SN - 2045-2322 VL - 7 PB - Macmillan Publishers Limited, part of Springer Nature CY - London ER - TY - THES A1 - Hintsche, Marius T1 - Locomotion of a bacterium with a polar bundle of flagella T1 - Fortbewegung eines Bakteriums mit einem polaren Flagellenbündel BT - insights into movement and navigation by fluorescence high speed microscopy BT - Erkentnisse über Bewegung und Navigation mittels Hochgeschwindigkeitsfluoreszenzmikroskopie N2 - Movement and navigation are essential for many organisms during some parts of their lives. This is also true for bacteria, which can move along surfaces and swim though liquid environments. They are able to sense their environment, and move towards environmental cues in a directed fashion. These abilities enable microbial lifecyles in biofilms, improved food uptake, host infection, and many more. In this thesis we study aspects of the swimming movement - or motility - of the soil bacterium (P. putida). Like most bacteria, P. putida swims by rotating its helical flagella, but their arrangement differs from the main model organism in bacterial motility research: (E. coli). P. putida is known for its intriguing motility strategy, where fast and slow episodes can occur after each other. Up until now, it was not known how these two speeds can be produced, and what advantages they might confer to this bacterium. Normally the flagella, the main component of thrust generation in bacteria, are not observable by ordinary light microscopy. In order to elucidate this behavior, we therefore used a fluorescent staining technique on a mutant strain of this species to specifically label the flagella, while leaving the cell body only faintly stained. This allowed us to image the flagella of the swimming bacteria with high spacial and temporal resolution with a customized high speed fluorescence microscopy setup. Our observations show that P. putida can swim in three different modes. First, It can swim with the flagella pushing the cell body, which is the main mode of swimming motility previously known from other bacteria. Second, it can swim with the flagella pulling the cell body, which was thought not to be possible in situations with multiple flagella. Lastly, it can wrap its flagellar bundle around the cell body, which results in a speed wich is slower by a factor of two. In this mode, the flagella are in a different physical conformation with a larger radius so the cell body can fit inside. These three swimming modes explain the previous observation of two speeds, as well as the non strict alternation of the different speeds. Because most bacterial swimming in nature does not occur in smoothly walled glass enclosures under a microscope, we used an artificial, microfluidic, structured system of obstacles to study the motion of our model organism in a structured environment. Bacteria were observed in microchannels with cylindrical obstacles of different sizes and with different distances with video microscopy and cell tracking. We analyzed turning angles, run times, and run length, which we compared to a minimal model for movement in structured geometries. Our findings show that hydrodynamic interactions with the walls lead to a guiding of the bacteria along obstacles. When comparing the observed behavior with the statics of a particle that is deflected with every obstacle contact, we find that cells run for longer distances than that model. Navigation in chemical gradients is one of the main applications of motility in bacteria. We studied the swimming response of P. putida cells to chemical stimuli (chemotaxis) of the common food preservative sodium benzoate. Using a microfluidic gradient generation device, we created gradients of varying strength, and observed the motion of cells with a video microscope and subsequent cell tracking. Analysis of different motility parameters like run lengths and times, shows that P. putida employs the classical chemotaxis strategy of E. coli: runs up the gradient are biased to be longer than those down the gradient. Using the two different run speeds we observed due to the different swimming modes, we classify runs into `fast' and `slow' modes with a Gaussian mixture model (GMM). We find no evidence that P. putida's uses its swimming modes to perform chemotaxis. In most studies of bacterial motility, cell tracking is used to gather trajectories of individual swimming cells. These trajectories then have to be decomposed into run sections and tumble sections. Several algorithms have been developed to this end, but most require manual tuning of a number of parameters, or extensive measurements with chemotaxis mutant strains. Together with our collaborators, we developed a novel motility analysis scheme, based on generalized Kramers-Moyal-coefficients. From the underlying stochastic model, many parameters like run length etc., can be inferred by an optimization procedure without the need for explicit run and tumble classification. The method can, however, be extended to a fully fledged tumble classifier. Using this method, we analyze E. coli chemotaxis measurements in an aspartate analog, and find evidence for a chemotactic bias in the tumble angles. N2 - Bewegung und Navigation sind für viele Organismen in einigen Bereichen ihres Lebens unerlässlich. Dies gilt auch für Bakterien, die sich entlang von Oberflächen bewegen und durch Flüssigkeiten schwimmen können. Sie sind in der Lage, ihre Umgebung wahr zu nehmen und sich gezielt auf Signale in der Umwelt zuzubewegen. Diese Fähigkeiten ermöglichen mikrobielle Lebenszyklen in Biofilmen, verbesserte Nahrungsaufnahme, Wirtsinfektion und vieles mehr. In dieser Arbeit untersuchen wir Aspekte der Schwimmbewegung - oder Motilität - des Bodenbakteriums Pseudomonas putida (P. putida). Wie die meisten Bakterien schwimmt P. putida durch Rotation seiner schraubenförmigen Flagellen, aber ihre Anordnung unterscheidet sich vom Hauptmodellorganismus in der bakteriellen Motilitätsforschung: Escherichia coli (E. coli). P. putida ist bekannt für seine faszinierende Motilitätsstrategie, bei der schnelle und langsame Episoden hintereinander auftreten können. Bislang war nicht bekannt, wie diese beiden Geschwindigkeiten erzeugt werden können und welche Vorteile sie diesem Bakterium bringen können. Normalerweise sind die Flagellen, die Hauptkomponente der Schuberzeugung bei Bakterien, mit herkömmlicher Lichtmikroskopie nicht zu beobachten. Um dieses Verhalten zu verdeutlichen, haben wir daher eine Fluoreszenzfärbetechnik an einem Mutantenstamm dieser Spezies eingesetzt, um die Flagellen spezifisch zu markieren und gleichzeitig den Zellkörper nur schwach gefärbt zu lassen. Dies ermöglichte es uns, die Geißeln der schwimmenden Bakterien mit hoher räumlicher und zeitlicher Auflösung mit einem maßgeschneiderten Hochgeschwindigkeits-Fluoreszenzmikroskopie-Setup darzustellen. Unsere Beobachtungen zeigen, dass P. putida in drei verschiedenen Modi schwimmen kann. Erstens kann es mit den Flagellen den Zellkörper vorwärts drücken, was der wichtigste Modus der Schwimmmotilität ist, der zuvor von anderen Bakterien bekannt war. Zweitens kann es mit den Flagellen den Zellkörper hinter sich her ziehen, was in Situationen mit mehreren Flagellen für nicht möglich gehalten wurde. Schließlich kann es sein Flagellenbündel um den Zellkörper wickeln, was zu einer um den Faktor zwei verlangsamten Geschwindigkeit führt. In diesem Modus befinden sich die Flagellen in einer anderen physikalischen Konformation mit einem größeren Radius, so dass der Zellkörper hineinpassen kann. Diese drei Schwimmmodi erklären die vorherige Beobachtung von zwei Geschwindigkeiten sowie das nicht strenge Abwechseln der verschiedenen Geschwindigkeiten. Da das Schwimmen von Bakterien in der Natur nicht in glattwandigen Glaskammern unter dem Mikroskop stattfindet, haben wir ein künstliches, mikrofluidisches, strukturiertes System von Hindernissen verwendet, um die Bewegung unseres Modellorganismus in einer strukturierten Umgebung zu untersuchen. Bakterien wurden in Mikrokanälen mit zylindrischen Hindernissen unterschiedlicher Größe und mit unterschiedlichen Abständen mit Videomikroskopie und Zelltracking beobachtet. Wir analysierten Turn-Winkel, Run-Zeiten und Run-Längen, die wir mit einem Minimalmodell für die Bewegung in strukturierten Geometrien verglichen haben. Unsere Ergebnisse zeigen, dass hydrodynamische Wechselwirkungen mit den Wänden zu einer Leitung der Bakterien entlang von Hindernissen führen. Vergleicht man das beobachtete Verhalten mit der Statik eines Partikels, das bei jedem Hinderniskontakt umgelenkt wird, so stellt man fest, dass Zellen über längere Strecken Laufen als in dieses Modell. Die Navigation in chemischen Gradienten ist eine der Hauptapplikation der Motilität bei Bakterien. Wir untersuchten die Schwimmreaktion von P. putida Zellen auf chemische Reize (Chemotaxis) des gängigen Lebensmittelkonservierungsmittels Natriumbenzoat. Mit einem mikrofluidischen Gradientengenerator erzeugten wir Gradienten unterschiedlicher Stärke und beobachteten die Bewegung der Zellen mit einem Videomikroskop und anschließendem Zelltracking. Die Analyse verschiedener Motilitätsparameter wie Lauflängen und -zeiten zeigt, dass P. putida die klassische Chemotaxiestrategie von E. coli anwendet: Läufe gradientenaufwärts sind im Mittel länger sein als solche gradientenabwärts. Mit den beiden verschiedenen Laufgeschwindigkeiten, die wir aufgrund der unterschiedlichen Schwimmmodi beobachtet haben, klassifizieren wir Läufe in schnelle und langsame Modi mit einem "Gaussian Mixture Model" (GMM). Wir finden keinen Beweis dafür, dass P. putida seine Schwimmmodi nutzt, um Chemotaxis durchzuführen. In den meisten Studien zur bakteriellen Motilität wird das Zelltracking verwendet, um die Trajektorien einzelner schwimmender Zellen zu erfassen. Diese Trajektorien müssen dann in Lauf- und Wendeabschnitte (Runs und Turns) zerlegt werden. Mehrere Algorithmen wurden zu diesem Zweck entwickelt, aber die meisten erfordern eine manuelle Abstimmung einer Reihe von Parametern oder umfangreiche Messungen mit chemotaktischen Mutantenstämmen. Zusammen mit unseren Mitarbeitern haben wir ein neuartiges Motilitätsanalyseschema entwickelt, das auf verallgemeinerten Kramers-Moyal-Koeffizienten basiert. Aus dem zugrunde liegenden stochastischen Modell können viele Parameter wie Lauflänge etc. durch ein Optimierungsverfahren abgeleitet werden, ohne dass eine explizite Run und Turn Klassifizierung erforderlich ist. Das Verfahren kann jedoch zu einem vollwertigen Klassifizierer ausgebaut werden. Mit dieser Methode analysieren wir E. coli Chemotaxis Messungen in einem Gradienten eines Aspartat analogen Chemoattractors und finden Beweise für eine chemotaktische Variation der Tumble-Winkeln. KW - bacteria KW - motility KW - chemotaxis KW - Bakterien KW - Motilität KW - Chemotaxis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-426972 ER - TY - JOUR A1 - Gómez-Nava, Luis A1 - Grossmann, Robert A1 - Hintsche, Marius A1 - Beta, Carsten A1 - Peruani, Fernando T1 - A novel approach to chemotaxis BT - active particles guided by internal clocks JF - epl : a letters journal exploring the frontiers of physics N2 - Motivated by the observation of non-exponential run-time distributions of bacterial swimmers, we propose a minimal phenomenological model for taxis of active particles whose motion is controlled by an internal clock. The ticking of the clock depends on an external concentration field, e.g., a chemical substance. We demonstrate that these particles can detect concentration gradients and respond to them by moving up- or down-gradient depending on the clock design, albeit measurements of these fields are purely local in space and instantaneous in time. Altogether, our results open a new route in the study of directional navigation: we show that the use of a clock to control motility actions represents a generic and versatile toolbox to engineer behavioral responses to external cues, such as light, chemical, or temperature gradients. Y1 - 2020 U6 - https://doi.org/10.1209/0295-5075/130/68002 SN - 0295-5075 SN - 1286-4854 VL - 130 IS - 6 PB - IOP Publ. Ltd. CY - Bristol ER - TY - GEN A1 - Alirezaeizanjani, Zahra A1 - Großmann, Robert A1 - Pfeifer, Veronika A1 - Hintsche, Marius A1 - Beta, Carsten T1 - Chemotaxis strategies of bacteria with multiple run modes T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1418 KW - instability KW - flagellum KW - exploit KW - time Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-519098 SN - 1866-8372 IS - 22 ER - TY - JOUR A1 - Alirezaeizanjani, Zahra A1 - Großmann, Robert A1 - Pfeifer, Veronika A1 - Hintsche, Marius A1 - Beta, Carsten T1 - Chemotaxis strategies of bacteria with multiple run modes JF - Science advances N2 - Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats. KW - exploit KW - flagellum KW - instability KW - time Y1 - 2020 U6 - https://doi.org/10.1126/sciadv.aaz6153 SN - 2375-2548 VL - 6 IS - 22 PB - American Association for the Advancement of Science CY - Washington ER -