Movies from the Lew Lab
Below are links to some of the movies scattered throughout the website. They may be useful in support of teaching in Biology, and are offered (with brief summaries) for educational purposes. Please feel free to share and adapt them under a Creative Commons license of Attribution 4.0 International. Please attribute to Movies from the Lew Lab.
Growth of Neurospora crassa colonies
In preparation for various experiments, colonies are inoculated at one side of a standard Petri dish, usually
on dialysis tubing overlaying growth medium (plus 2% w/v agar). Here is a time lapse movie of colony growth overnight.
[5.5 MB .mov format] [2.1 MB .wmv format] [0.9 MB .mp4 format]
At the colony edge, leading hyphae are the pioneers. Behind the edge,
a network of smaller hyphae fill in the gaps, creating a complicated network of filaments (the mycelium) that maximizes the absorptive area of the fungal colony.
[5.5 MB .mov format] [1.2 MB .mp4 format]
At the tip, coordinated tip expansion and inclusion of membrane
and wall material are the causes of the characteristic hyphal shape. Here are examples of tip growth of Neurospora
[22.4 MB .mov format]
[11.8 MB .mp4 format]
and Saprolegnia.
[1.7 MB .mov format] [1.6 MB .mp4 format].
Behind the tip, cytoplasm migrates towards the growing edge of the
colony. The nature of the cytoplasm flow is dual: both particle movement driven by molecular motors along the cytoskeleton, and pressure-driven
mass (Poiseuille) flow.
[14.4 MB .avi format] [0.64 MB .mp4 format]
Some of our movies are made for illustrative purpose,
to explain how experiments are done. This movie was made by Shanar Nasserifar to explain how to impale a trunk hypha with a double-barrel
micropipette. Near the end of the movie, the micropipette is removed from the hypha, causing the expulsion of some cytoplasm due to the
high turgor of the cell. The puncture wound rapidly heals.
[10.2 MB .mov format] [3.8 MB .mp4 format]
Here is another movie made for illustrative purpose.
This movie was made by Ahmed Hamam to show dual impalements into a trunk hypha for cable-corrected current-voltage measurements. The hypha isn't
affected, based on continued mass flow after the impalements.
[9.8 MB .mov format] [1.3 MB .mp4 format]
This movie shows how oxygen flux is measured along growing hyphal tips.
The probe is moved near and away from the hypha to sample the diffusive gradient of oxygen caused by respiration. This movie is in
real-time.
[8.4 MB .mov format] [3.4 MB .mp4 format]
Here, the hyphae were stained with a mitochondria-specific
fluorescent dye. Dual channels (brightfield and fluorescence) have been merged to show the migration of tip-localized mitochondria with the tip during tip
growth in Neurospora.
[7.5 MB .mov format] [5.6 MB .mp4 format]
Measurements in Arabidopsis thaliana root hairs
Root hairs of the model organisms
Arabidopsis crassa are a favorite for cell biologists interested in cell growth in higher plants. Here is an
example of a dual impalement into a root hair: with a pressure probe to measure (and modify) the hydrostatic pressure of
the cell and with a double barrel micropipette to measure the electrical properties of the cell.
[3.5 MB .mov format] [0.78 MB .mp4 format]
In a continuation of the movie above, here is the injection of
silicon oil (to increase the hydrostatic pressure of the cell). The cell's electrical properties are unaffected by these dramatic changes, until the
tip bursts.
[15.4 MB .mov format] [1.4 MB .mp4 format]
Triple impalements made it possible to explore the effect of hydrostatic
pressure on cell-to-cell coupling between adjacent root hairs.
[8.6 MB .mov format] [2.9 MB .mp4 format]
Eremosphaera viridis imaging
The unicellular Chlorophyte Eremosphaera viridis offers many
advantages for the study of algal physiology, of which one is its extraordinary beauty. Here is a three-dimensional reconstruction of the cell, imaging
mitochondria (green) and chloroplasts (red) in two channels (merged in the middle panel).
[10.3 MB .mov format] [3.3 MB .mp4 format]
At high light irradiance, chloroplasts of the
Eremosphaera viridis cell migrate to the center, to surround the nucleus.
[5.7 MB .mov format] [2.3 MB .mp4 format]
With dual imaging of mitochondria (green) and
chloroplasts (red), it is clear that mitochondria remain in the periphery of the cell as the chloroplasts move to the center and surround
the nucleus.
[7.2 MB .mov format] [3.9 MB .mp4 format]
A 'show-and-tell' impalement of Eremosphaera viridis (produced
by Sandra Khine) shows how measurements of the cell's electrical properties are done.
[2.0 MB .mov format] [0.6 MB .mp4 format]
Dual probe measurements of Eremosphaera viridis (an experiment
by me at the
BioCurrents Research Center at MBL in Woods Hole). The transport of oxygen and ions were measured simultaneously by measuring their diffusive gradients
surrounding the cell.
[645 kB .mov format] [592 kB .mp4 format]
A X100 oil objective was used to image individual chloroplasts and
connecting cytoplasmic strands (some of which contain mitochondria) at the cell periphery (the top) of an Eremosphaera viridis cell using DIC (Differential
Interference Contrast). The images show the motion of the cytoplasm and organelles over a 1 minute period, and reveal the complicated
architecture of individual chloroplasts.
[3.9 MB .mov format] [2.1 MB .mp4 format]
The large size of Eremosphaera viridis makes a variety of cellular
manipulations fairly easy. Here, Kevin Cross is injecting the cell with silicon oil to change the internal pressure of the cell (up to about
1,200 kiloPascals from its normal turgor of about 700 kiloPascal). The walls are so tough the cell barely changes size.
The movie runs forward, then backwards.
[2.3 MB .mov format] [1.2 MB .mp4 format]
Here's a movie of Eremosphaera viridis being cultured in the laboratory.
Light is provided at about 50 umol photons per square meter per second from a fluorescent lamp. The constant rotatory motion ensures an adequate
supply of carbon dioxide for photosynthesis in this autotrophic culture [2.0 MB .mov format][1.2 MB .mp4 format]. The culture
is described as LB (live bacteria). Bacterial density is low, because bacteria require a carbon sources to grow, and must feed on the very small amount of nutrients
that leak out of the Eremosphaera cells.
Cytoplasmic Streaming in Onion
These movies were made in support of optical trapping experiments
for a Biophysics lab by Sandra Khine and me. Here, particle movement along tracks is shown around the nucleus in an onion epidermal
peel.
[2.4 MB .mov format] [0.9 MB .mp4 format]
Along the sides of the cell, where a thin layer of cytoplasm is
found, particle movement is bidirectional.
[4.4 MB .mov format] [2.3 MB .mp4 format]
Dark field provides a more visually appealing image of the
streaming, shown here with a X10 objective to view multiple cells.
[625 kB .mov format] [758 kB .mp4 format]
Staying with visual appeal, phase contrast provides a different perspective on
the nature of the
streaming, shown here with a X10 objective to view multiple cells.
[1.1 MB .mov format] [1.4 MB .mp4 format]
Cytoplasmic Streaming and Growth in Chara
These movies were made by Professor Mary Bisson and me in
support of Chara electrophysiology experiments for a Biophysics lab. Here, particle movement along tracks is shown behind the sheath of
choroplasts in the periphery of the cylindrical Chara cell.
[30.1 MB .mov format] [9.4 MB .mp4 format]
Through the diagonal of the cylindrical cell is a chloroplast
free line known as the indifferent zone; particles move in opposite directions depending on which side of the indifferent zone they are.
[28.1 MB .mov format] [9.4 MB .mp4 format]
Here is a view focussed on the medial edge of the Chara cell,
to give an idea about the bulk nature of the cytoplasmic flow.
[12.3 MB .mov format] [4.1 MB .mp4 format]
Courtesy of Kevin Cross, here is a silicon oil
droplet in the cytoplasm of the Chara cell. The oil droplet migrates to the indifferent zone, and rotates as it is
jostled by particulate streaming on either side of the zone.
[6.3 MB .mov format] [6.2 MB .mp4 format]
Again, courtesy of Kevin Cross, injection of
the silicon oil into the cytoplasm of the Chara cell and its migration are shown with a X4 objective under dark field.
Because the silicon oil should not interact with myosin molecular motors, it is being 'pushed' by the material that is
interacting with the molecular motors.
[0.74 MB .mov format] [1.0 MB .mp4 format]
We ran a time lapse (for 1.27 days) to show the growth of Chara
in a newly planted culture. Dark shadows at times 465 and 955 minutes are snails cruising along the glass walls of the aquarium. You can see the
helical twist as the internode cell elongates, and the indifferent zone (see above). The gyrations as the plant elongates are known as circumnutations
--something studied by the famous botanist Charles Darwin (also known for his Theory of Evolution).
[3.1 MB .mov format] [4.1 MB .mp4 format]
A second time lapse of the same plant, but growth has
accelerated. The helical twist as it grows is clearer. It is even possible to see the movement of particles inside the cell (somewhat jerky
due to the 5 minute time lapse) due to cytoplasmic streaming.
[3.4 MB .mov format] [5.0 MB .mp4 format]