Abstract:

This dataset includes the video and statistics of bacteria (Pseudomonas aeruginosa PA01) near and on an oil-water interface using a microscope. In addition to the ensemble behavior of the bacteria, a gallery of distinct trajectories of individual swimmers on and near fluid interfaces is included. In addition, Brownian diffusive paths for passive adsorbed bacteria, curvilinear trajectories including curly paths and pirouette motions are also presented. Data contained in every file is described in the Word document titled “Data Information”. This dataset supports the publication of Deng, Jiayi; Mehdi Molaei, Nicholas G. Chisholm and Kathleen J. Stebe. (2020). Motile Bacteria at Oil-Water Interfaces: Pseudomonas aeruginosa. Langmuir, 36, 25, 6888-6902. doi:10.1021/acs.langmuir.9b03578.

Suggested Citation:

Deng, Jiayi, Mehdi Molaei, Nicholas G. Chisholm, and Kathleen J. Stebe. 2020. Dataset for: Motile bacteria at oil-water interfaces: Pseudomonas aeruginosa. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-7zhg-yj18

Publications:

Deng, J., Molaei, M., Chisholm, N. G., & Stebe, K. J. (2020). Motile Bacteria at Oil–Water Interfaces: Pseudomonas aeruginosa. Langmuir, 36(25), 6888–6902. doi:10.1021/acs.langmuir.9b03578

Purpose:

Characterization of individual bacteria. This work potentially impacted nutrient cycles for bacteria on or near interfaces in nature. This work will also have implications in microrobotics, as active colloids in general and bacteria in particular are used to cargo in this burgeoning field.

Data Parameters and Units:

velocity (μm/s), viscosity (mPa·s), surface tension (mN/m), diffusivity (μm^2/s), curvature (μm-1), frame rate (60 frames per second)

Methods:

Pseudomonas aeruginosa PA01 Wild Type was inoculated and cultured in 10mL Lysogeny (LB) broth using a 50mL conical flask with a porous cap. The cultures were placed on a table-top shaker at 250rpm at 37.0◦C for 17 hours. They were then centrifuged at 3500rpm for 10min. After centrifugation, the sedimentation was washed and re-suspended with Tris-based motility medium (50mM Tris-HCl, pH = 7.5, 5mM MgCl2, 5mM glucose, 200mM NaCl and 100mM KCl). This centrifugation and resuspension process was repeated twice to prepare a bacteria suspension. The cell concentration was determined by optical density measurements at 630nm using Infinite 200 PRO. The optical density for our experiments was set to be 0.05. A cylindrical vessel with an inner diameter of 1cm is covered with a glass coverslip at the bottom and sealed with vacuum grease. The bottom half of the cylinder is aluminum, and the top half is Teflon. These two parts intersect in the middle and pin the interface, thus creating a planar oil-water interface, Fig. 1a. The aqueous bacteria suspension of approximately 115µL is placed in the bottom of the vessel, and 500µL hexadecane is then pipetted into the vessel to form an oil-water interface. We also varied the viscosity of the non-aqueous phase, using air to give a nearly vanishing viscosity ratio and different silicone oils to yield viscosity ratios between 1 and 300. The bacteria motion was imaged using an upright microscope (Zeiss AxioImager M1m) in bright field with 50x magnification. The videos are recorded by a high-speed camera at 61 frames per second. We calculated the background noise by averaging over all frames in the video and subtract that noise from the original images. Bacteria on the interface appear as ellipsoidal dark regions with an area of approximately 2 µm2, while bacteria adjacent the interface appear white as they are out of the interfacial plane. Bacteria that remain dark in color throughout the observation time (up to 1min) are inferred to be adhered to the interface. We defined the oil-water interface as the x-y plane, where the x-axis is the horizontal direction of the image. The coordinate z is defined downward into the fluid.

Instruments:

630nm using Infinite 200 PRO; Zeiss AxioImager M1m microscope; table-top shaker; centrifuge

Individual Files: