Bioluminescent response of individual dinoflagellate cells to hydrodynamic stress measured with millisecond resolution in a microfluidic device

Abstract

SUMMARYDinoflagellate bioluminescence serves as a model system for examining mechanosensing by suspended motile unicellular organisms. The response latency, i.e. the delay time between the mechanical stimulus and luminescent response, provides information about the mechanotransduction and signaling process, and must be accurately known for dinoflagellate bioluminescence to be used as a flow visualization tool. This study used a novel microfluidic device to measure the response latency of a large number of individual dinoflagellates with a resolution of a few milliseconds. Suspended cells of several dinoflagellate species approximately 35 μm in diameter were directed through a 200 μm deep channel to a barrier with a 15 μm clearance impassable to the cells. Bioluminescence was stimulated when cells encountered the barrier and experienced an abrupt increase in hydrodynamic drag, and was imaged using high numerical aperture optics and a high-speed low-light video system. The average response latency for Lingulodinium polyedrum strain HJ was 15 ms (N>300 cells) at the three highest flow rates tested, with a minimum latency of 12 ms. Cells produced multiple flashes with an interval as short as 5 ms between individual flashes, suggesting that repeat stimulation involved a subset of the entire intracellular signaling pathway. The mean response latency for the dinoflagellates Pyrodinium bahamense, Alexandrium monilatum and older and newer isolates of L. polyedrum ranged from 15 to 22 ms, similar to the latencies previously determined for larger dinoflagellates with different morphologies, possibly reflecting optimization of dinoflagellate bioluminescence as a rapid anti-predation behavior. Supplementary material available online at

Pyrocystis noctiluca represents an excellent bioassay for shear forces induced in ground-based microgravity simulators (clinostat and random positioning machine)

“…9, 29, 30 As a conclusion the emitted light of the dinoflagellates can be interpreted as direct measure of the intensity of perceived shear forces. Their response time was measured around 20 ms after mechanical impact on the cells and is described as one of the fastest reporter systems in nature.…”

Stress, Strain-Rate Analysis of Sub-Surface Driveway Plants

“…Silverberg et al (2012) present experimental and theoretical results on root buckling in plants. Latz et al (2008) and Kutschera & Niklas (2013) report cell "mechanosensing" in response to external stresses.…”

The artistry of dinoflagellate bioluminescence

“…So waves, flow along moving objects, or surge contain sufficient forces to stimulate bioluminescence [3]. Our previous research has examined the levels of mechanical forces required to stimulate bioluminescence, first using populations of cells within fully characterized flow conditions [4][5][6] and more recently for individual cells studied using microfluidics and atomic force microscopy [7,8]. Light originates from microsources within each dinoflagellate cell called scintillons, vesicles containing the luminescent chemistry [9,10].…”

“…The chemical reaction producing the light is activated by a rapid and complex series of biochemical and electrical steps that comprise the bioluminescence signaling pathway. The entire pathway, from mechanical stimulation to light production, is extremely rapid with a duration of less than 20 ms [7,11,12]. Our current research is investigating the signaling proteins involved in this pathway, in the process identifying elements of mechanical sensing that have been conserved in higher organisms [13].…”