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  - Theves, Matthias
A1  - Taktikos, J.
A1  - Zaburdaev, V.
A1  - Stark, H.
A1  - Beta, Carsten
T1  - Random walk patterns of a soil bacterium in open and confined environments
JF  - epl : a letters journal exploring the frontiers of physics
N2  - We used microfluidic tools and high-speed time-lapse microscopy to record trajectories of the soil bacterium Pseudomonas putida in a confined environment with cells swimming in close proximity to a glass-liquid interface. While the general swimming pattern is preserved, when compared to swimming in the bulk fluid, our results show that cells in the presence of two solid boundaries display more frequent reversals in swimming direction and swim faster. Additionally, we observe that run segments are no longer straight and that cells swim on circular trajectories, which can be attributed to the hydrodynamic wall effect. Using the experimentally observed parameters together with a recently presented analytic model for a run-reverse random walker, we obtained additional insight on how the spreading behavior of a cell population is affected under confinement. While on short time scales, the mean square displacement of confined swimmers grows faster as compared to the bulk fluid case, our model predicts that for large times the situation reverses due to the strong increase in effective rotational diffusion.
Y1  - 2015
U6  - https://doi.org/10.1209/0295-5075/109/28007
SN  - 0295-5075
SN  - 1286-4854
VL  - 109
IS  - 2
PB  - EDP Sciences
CY  - Mulhouse
ER  -