Abstract:
This is data from a study on how passive colloids move in bacterial-laden interfaces. The individual trajectories of particles were analyzed. This dataset shows that enhanced transport results from individual colloids being moved as cargo by the adhered bacteria. This dataset includes videos of particles in the interface between aqueous bacteria suspensions and hexadecane.
Suggested Citation:
Mehdi Molaei, Kathleen Stebe, Liana Vaccari. 2019. Interaction of Bacteria and Passive Colloids at Oil-Water Interfaces. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7MG7N3P
Data Parameters and Units:
2840_drift.csv: Drift displacement associated with the interfaces. frame, x, y.
2840_tm.csv: Trajectories of the 1 micron sphere at the interface of the bacteria suspension and oil. frame: frame number in the recorded image sequences, ecc: eccentricity of the particles and bacteria, mass: Integrated intensity of the particles in the images, particle: ID for trajectories of particles, x: x location of the particles in pixel, y: y location of the particles in pixel, Rg: Radius of the particles.
Cell_interface.csv: Trajectories of the bacteria just below the interface. x: x location of the particles in pixel, y: y location of the particles in pixel, mass: Integrated intensity of the particles in the images, Rg: Radius of the particles, Eccentricity: eccentricity of the particles and bacteria, frame: frame number in the recorded image sequences, time, particle: ID for trajectories of particles.
Cell_sublayer.csv: Trajectories of the bacteria just below the interface. File header information: x: x location of the particles in pixels, y: y location of the particles in pixels, mass: Integrated intensity of the particles in the images, Rg: Radius of the particles, Eccentricity: eccentricity of the particles and bacteria, frame: frame number in the recorded image sequences, time, particle: ID for trajectories of particles.
MSD files: Mean square displacement of different particles to measure the diffusion coefficient. File header information: lag time (s), MSD_experiment (um^2), MSD_model (um^2).
PDF_velocity files: Velocity of bacteria and different type of particle trajectories. File header information: Velocity (um/s), Probability density.
Recorder-Stream-2840.avi: Video of the bacteria-laden interfaces with passive tracer particles.
Video1_Curly.avi: Video of a particle exhibiting curly motion.
Video2_Diffusive.avi: Video of a particle exhibiting diffusive motion.
Video3_Persistent.avi: Video of a particle exhibiting persistent motion.
Video4_Mixed.avi: Video of a particle exhibiting both curly and persistent motion.
Methods:
Data analysis are performed using particle tracking codes in Python and Matlab. Raw Data are video files in avi format. The bacteria and particle positions of each video frame were extracted and stored in a python format.
Pseudomonas aeruginosa PA14DpelA were cultured in LB Medium in a table-top incubator at 37 1C. The bacteria were then centrifuged, decanted, and re-suspended in 0.154mmol NaCl solution. The bacteria suspension was diluted to the desired optical density, typically OD = 0.1–0.2 for particle tracking experiments, corresponding to cell concentration B108 cells mL 1, measured with a Tecan spectrophotometer at 630 nm, with 100 mL of suspension, averaged over 3 wells in a 96-well plate.
The particle-tracking measurements were performed in a 1.5 cm I.D. cylindrical vessel with an inner surface whose bottom half is aluminium and top half is Teflon. When the cell was filled to the appropriate level, the aluminium-Teflon seam pins the oil–water interface, creating a flat interface with no meniscus. The base of the cylinder rests on an untreated glass coverslip, sealed with silica vacuum grease. To begin each experiment, the cylinder was filled nearly to the seam with 0.5 mL of the relevant cleaned bacteria suspension. A spreading solution containing 12.5 mL charge-stabilized carboxy-functionalized polystyrene spheres (Invitrogen) with radius Rs = 0.5 mm in a mixture of 450 mL water and 250 mL isopropanol was prepared in advance and sonicated to disperse any colloidal aggregates. To introduce the colloids to the interface, a 1 mL droplet of the spreading solution was gently placed in contact with the aqueous surface. The solution wets the surface, and the colloids, which are slightly denser than water but hydrophobic, disperse across the interface. Droplets of hexadecane were then promptly placed on this system to form a film approximately 2 mm thick which covered the colloids and the aqueous suspension. Colloids were observed at the interface using an upright bright-field microscope with a 50 objective (Zeiss, NA 0.6). A camera (Zeiss AxioImager M1m) recorded a 200 mm by 150 mm field of view at 60 frames per second, which set the shortest lag time over which probe motion can be characterized. Probe trajectories were extracted from the video.
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