DROPPS at 2015 GoMRI Conference


Recent Publications

Imaging bacterial 3D motion using digital in-line holographic microscopy and correlation-based de-noising algorithm.

Molaei M, Sheng J.

Imaging bacterial 3D motion using digital in-line holographic microscopy and correlation-based de-noising algorithm.

Opt Express [Internet]. 2014;22(26):32119-32137. Publisher's VersionAbstract
Better understanding of bacteria environment interactions in the context of biofilm formation requires accurate 3-dimentional measurements of bacteria motility. Digital Holographic Microscopy (DHM) has demonstrated its capability in resolving 3D distribution and mobility of particulates in a dense suspension. Due to their low scattering efficiency, bacteria are substantially difficult to be imaged by DHM. In this paper, we introduce a novel correlation-based de-noising algorithm to remove the background noise and enhance the quality of the hologram. Implemented in conjunction with DHM, we demonstrate that the method allows DHM to resolve 3-D E. coli bacteria locations of a dense suspension (>107 cells/ml) with submicron resolutions (<0.5 µm) over substantial depth and to obtain thousands of 3D cell trajectories.

Statistical Mechanics of Zooplankton

Hinow P, Nihongi A, Strickler, Rudi J. Statistical Mechanics of Zooplankton. PloS one [Internet]. 2015;10(8). Publisher's VersionAbstract
Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar "microscopic" quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the "ecological temperature" of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean's swimming behavior.

Failed Escape: Solid Surfaces Prevent Tumbling ofEscherichia coli

Molaei M, Barry M, Stocker R, Sheng J.

Failed Escape: Solid Surfaces Prevent Tumbling ofEscherichia coli

. Physical review letters [Internet]. 2014;113(6):068103. Publisher's VersionAbstract
Understanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>103) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20  μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.

Facebook Feed