Microbiology Videos
This page
contains links to several QuickTime videos featuring live-action footage of
microorganisms. If you do not have the QuickTime plug-in, click
here [http://www.apple.com/quicktime/download] to download it
free of charge.
Allomyces Zoospore Release - AllomycesSpore-S.mov
Allomyces is an aquatic, saprotrophic fungus that
is found worldwide in soil and water. It reproduces asexually by converting the
contents of a sporangium into motile diploid zoospores. Here you can see one
zoospore slowly squeezing out of the pore in the sporangium. This spore will
swim away and attach to a suitable substrate, where it will retract the
flagellum, and grow into a new diploid body or thallus under suitable
conditions.
Credit: Henry
Mainwaring, Western Carolina University
Amoeba
- Amoeba-S.mov
In this clip the
pseudopodium, or false foot, is extending from the front of an amoeba using a
process that involves changes in the viscosity of the cytoplasm. The inner
flowing cytoplasm is called the endoplasm, and is in a liquid sol state. This
flows forward filling the pseudopodium. At the front, the endoplasm is
converted into the clear gel-like ectoplasm, which is located just under the
plasma membrane. At the rear of the amoeba, the ectoplasm is converted back
into endoplasm, and it flows forward to the front of the cell to be converted
back into ectoplasm.
Credit: Courtesy
of Graham R. Kent and Rebecca L. Turner, Smith College
Amoeba Pseudopodia - AmoebaPseudopodia-S.mov
Locomotion in
rhizopods, or amoebas, occurs by means of pseudopodia in a process called
amoeboid movement. Amoeba proteus
is a large unicellular organism that moves over its substrate by sending
extensions of its cytoplasm, called pseudopodia, in various directions. The
pseudopodia are capable of surrounding and engulfing food by phagocytosis. Even
though Amoeba has been
one of the most intensely studied organisms, the exact mechanism of its
movement is still not completely understood. However, the leading edge of the
amoeba is a clear zone that seems devoid of cytoplasmic organelles; this is
called the ectoplasm. The rest of the cytoplasm is called the endoplasm.
Fluorescence microscopy has shown the ectoplasm contains large amounts of
actin, the contractile protein common in muscle cells.
Credit: Henry
Mainwaring, Western Carolina University
C. elegans Crawling - CElegansCrawl-S.mov
Caenorhabditis
elegans, or C.
elegans, is a species of
nematode (roundworm) that normally lives in the soil and eats bacteria. The
worm shown here is crawling on an agar plate in a lab, demonstrating movements
similar to those it would normally use to move through the soil. Structures and
organs in this worm are clearly visible, and some of them are labeled in this
clip. Because an adult of this species is made up of only about 1000 cells, and
they are easy to raise in a lab, C. elegans has become a popular species for the
study of embryonic development. The adult shown here, like most adult C.
elegans, is a
self-fertilizing hermaphrodite: each adult produces both sperm and eggs, and
fertilization is internal. Adult hermaphrodites are one millimeter long.
Credit: Robert
P. Goldstein, UNC Chapel Hill
C. elegans Embryo Development (Time Lapse) - CElegansEmbryo-S.mov
C.
elegans,
the soil worm or nematode, is a useful species for the study of embryonic
development because the lineage and fates of all cells are known, and also
genetic techniques can be used to determine the function of specific genes.
This time-lapse film shows the first 15 hours of development from a fertilized
egg to a fully formed worm. The fertilized egg is about 50 microns long (1/20th
of a millimeter), and contains two nuclei. The nucleus on the right is from the
egg; the one on the left was contributed by the sperm at fertilization.
This
one cell will divide into all the cell types of the embryo, including muscle
cells, nerve cells, gut cells, etc. The fates of some cells are determined
quite early. For example, at 00:56:01 (hours:minutes:seconds of real time)
there are eight cells. The cell on the lower left with the clearly visible
nucleus in this frame is the cell that will make all the cells of the entire
gut of the adult worm. Other cells will give rise to muscle cells, nerve cells,
etc.
The mass of cells elongates into a worm shape
(which begins around 5:32:01 in this film), and during this period some of the
cells that have formed are becoming functional muscle cells, so the embryo
starts to twitch and then crawl around inside the eggshell (starts around
7:24:01).
In
the final frame, the head is near the top, and the tail is near the bottom.
Credit: Robert
P. Goldstein, UNC Chapel Hill
Chlamydomonas
- Chlamydomonas-S.mov
Chlamydomonas
is a unicellular green alga with two anterior flagella, and a single cup-shaped
chloroplast. Each cell is about 10 micrometers across. This cell is viewed with
Nomarski optics, which gives an image that appears to have three-dimensional
relief. The smooth space at the anterior end is the contractile vacuole,
contraction of which can be seen clearly in this clip. This organelle is
involved in water regulation in Chlamydomonas. By expelling a solution hypotonic to
that in the cell, the contractile vacuole counters the osmotic movement of
water into the cell. The slightly larger circular structure at the other end is
the pyrenoid, within the chloroplast, where starch is deposited. The textural
relief around the pyrenoid is due to the thylakoid membrane stacks in the
chloroplast.
Credit: Michael
Clayton, University of Wisconsin, Madison
Diatoms - VariousDiatoms-S.mov
Seen on this clip is the motility of several species of
aquatic organisms collected from the Maunesha River in Wisconsin, just after
the ice melted. We can recognize four species, including two pennate diatoms.
The smaller one is Navicula
spp., while the longer more slender one is Nitzchia sp. Three filaments of the
cyanobacterium Oscillatoria
are also seen, as well as the eukaryotic green alga Spirogyra, the bright green filament on the upper
left.
Credit: Michael
Clayton, University of Wisconsin, Madison
Diatoms
Moving - DiatomsMoving-S.mov
This
clip shows motile pennate diatoms of the species Navicula, collected from the Maunesha River in
Wisconsin, just after the winter ice melted in March, 2001. Diatoms are
possibly the most important primary producers in the aquatic environment. Each
cell is enclosed in two valves, like the top and bottom of a petri dish. There
are two classes of diatoms, based on the shape of their valves when viewed
straight on. Centric diatoms are radially symmetric, while pennate
diatoms are bilaterally symmetric, as seen here for Navicula. The cells in this clip appearing more
pointed at the ends and wider in the middle are viewed from straight on at one
valve, whereas the ones appearing more uniform in width with blunter ends are
seen from the side. The latter is called the “girdle view” because
it shows the girdle, a longitudinal trough in the side of the cell wall thought
to be involved in motility of these cells. Going across the right side of the
screen you can also see an example of the motility of the filamentous
cyanobacterium Oscillatoria.
Credit: Michael
Clayton, University of Wisconsin, Madison
Dinoflagellate
- Dinoflagellate-S.mov
Locomotion in
the protists occurs either by the beating of hair-like structures (cilia or
flagella), or by means of pseudopodia in a process called amoeboid movement.
Compared to the cell’s body length, flagella are long and are less
numerous than cilia. Most flagellated cells have only one or two flagella.
Motility in Peridinium
is typical of many dinoflagellates. There is a posterior flagellum that
provides forward motion, and a second flagellum located in a groove that wraps
around or “girdles” the equatorial region of the cell. Although the
girdle flagellum is difficult to see, it contributes to the cell’s
rotating or gyrating motion as it moves through the water. The word dino- comes from the Greek meaning “to
whirl.”
Credit: Courtesy
of Graham R. Kent and Rebecca L. Turner, Smith College
Euglena
- Euglena-S.mov
Seen
here are two protistan cells of the species Euglena acus. This species is in the euglenoid group
of the clade Euglenozoa. Euglena
and closely related protists are characterized by having a pocket at the
anterior end from which emerges a flagellum. In this clip, the use of phase
contrast microscopy allows us to view the flagellum at the anterior (rounded)
end. The posterior end is more pointed. These cells are anchored at the
posterior end by nail polish, and you can see their swimming behavior. The
small specks swarming around them are bacteria, which allows you to see the
relative size of prokaryotes and eukaryotic protists.
Credit: Michael
Clayton, University of Wisconsin, Madison
Euglena Motion - EuglenaMotion-S.mov
The
Euglena acus in this
clip was treated with NiSO4. Nickel ion paralyzes the flagellum. We
can see the extreme shape changes of the cell, showing clearly the great
flexibility of the pellicle, or specialized cell membrane. You can see the
paralyzed anterior flagellum, at the left end of the cell throughout most of
this clip. At the anterior end, you can see the reddish spot which functions as
a light detector.
Credit: Michael
Clayton, University of Wisconsin, Madison
Oscillatoria - Oscillatoria-S.mov
Shown
in this movie are three filamentous bacteria from the domain Bacteria,
specifically the group known as Cyanobacteria (previously the blue-green
algae). This species is named Oscillatoria, and you can see a short filament moving along and around a
much longer one in a gliding motion that has been called “barber-poling”.
These bacteria do not have flagella, and the molecular basis for their motility
remains somewhat of a mystery.
Credit: Michael
Clayton, University of Wisconsin, Madison
Paramecium Cilia - ParameciumCilia-S.mov
Locomotion in
the protists occurs either by the beating of hair-like structures (cilia or
flagella), or by means of pseudopodia in a movement called amoeboid movement.
In Paramecium,
movement is accomplished by the coordinated beating by many short hair-like
appendages called cilia. The cilia form longitudinal rows along the entire body
of the cell and into the oral groove. Forward and backward movement is easily
accomplished by the beating of the cilia. The beating action of the cilia
produces a slow rotation of the Paramecium as it moves through the water. The cilia in the oral groove
propel food particles to the bottom of the gullet where the food can be
ingested by phagocytosis.
Credit: Courtesy
of Graham R. Kent and Rebecca L. Turner, Smith College
Paramecium Vacuole - ParameciumVacuole-S.mov
The single
celled ciliated protozoan Paramecium is found in fresh water. It continually pulls water in by
osmosis. A specialized organelle, the contractile vacuole, collects water from
the cell and pumps it out with regular contractions. Two such contractions can
be seen in this video clip.
Credit: Henry
Mainwaring, Western Carolina University
Phlyctochytrium Zoospore Release - PhlyctochytriumSpore-S.mov
The aquatic
fungus Phlyctochytrium
reproduces asexually by converting the entire contents of the flasked shaped
body, or thallus, into flagellated zoospores. Here you can see a number of
zoospores being rapidly released through a pore in the flask. These spores swim
away and attach to a suitable substrate, where they retract the flagellum, and
grow into a new thallus under suitable conditions.
Credit: Henry
Mainwaring, Western Carolina University
Plasmodial Slime Mold - SlimeMoldZoom-S.mov
This clip shows an overview of the
plasmodial slime mold Physarum polycephalum. Shown here is a feeding plasmodium, a
single cell containing many nuclei that have arisen by repeated mitoses of the
original nucleus. As the magnification increases, details of the branching
structure are visible. This stage is shown at much higher magnification in a
separate clip, 28-29-SlimeMoldStreaming.
Credit: Michael
Clayton, University of Wisconsin, Madison
Plasmodial Slime Mold Streaming - SlimeMoldStreaming-S.mov
This
clip shows a piece of the plasmodial slime mold Physarum polycephalum. This organism does not photosynthesize,
it is heterotrophic and must feed. Shown here is the feeding stage known as the
plasmodium, which moves around as an amoeboid mass, engulfing its food by
phagocytosis. The feeding plasmodium is a single cell containing many nuclei
that have arisen by repeated mitoses of the original nucleus. The single mass
of cytoplasm contains fine channels within which cytoplasm streams back and
forth as can be seen in this video clip. Cytoplasmic streaming functions to
distribute nutrients and oxygen to other parts of the cell, as well as helping
in amoeboid movement of the plasmodium.
Credit: Michael
Clayton, University of Wisconsin, Madison
S.
typhimurium
Swimming - SalmonellaFlagella-S.mov
This
is a dark field video of bacterial cells of the species Salmonella
typhimurium, filmed with
a full intensity beam. Due to light scattering, the cells appear greater than
their actual size, and the flagellum on each cell can be seen clearly. Many
bacteria swim by rotating their flagella in a helical manner. In media of
normal viscosity, the flagella are moving too fast for their helical waveform
to be seen. In the second half of the clip, the cells are placed in a highly
viscous medium. The flagellar rotation is now slow enough for the waveform to
be seen easily. The direction of rotation can be changed, and thus the cells
are able to change their direction. Flagellar motion is accomplished by means
of a set of proteins that act together as a motor, fueled by a proton gradient
across the cell membrane.
Credit: Robert
Macnab, Professor of Molecular Biophysics and Biochemistry at Yale University
T Cell Receptors - TCellReceptors-S.mov
This clip shows a T cell with fluorescently labeled (via a GFP-fusion) T cell receptor-associated molecules. The video shows the events as a T cell meets and recognizes an antigen-bearing B cell. In brief, it shows the ongoing process of molecular recognition that occurs when immune T cells detect a foreign particle in the animal. The video is a montage of four panels (clockwise from upper left). The first shows the differential interference contrast (DIC) image, the second shows the intracellular calcium levels as determined by using a fluorescent calcium sensitive dye (calcium levels are color-coded from blue up to red), the third shows the distribution (along the cell surface) of the transmembrane T cell receptor molecule (green-red color scale), and the fourth is a three-dimensional projection of the “cap” complex at the interface of the T cell and the B cell. This latter image shows the dynamic nature of the molecular recognition event. The key molecules are eventually “corralled” into the center of the interface toward the end of the movie.
Credit: Dr. Matthew Krummel, UCSF,
Department of Pathology
Volvox
Colony - VolvoxColony-S.mov
This footage focuses through a colony of Volvox, a colonial green alga, at 200x
magnification. While Chlamydomonas
is most closely related to primitive ancestors of the Volvocine line, Volvox is the most recently evolved. Chlamydomonas is unicellular, while other members of
this phylogenetic group can be thought of as multicellular versions of Chlamydomonas. A Volvox colony is a hollow sphere, made up of
128 or 256 cells embedded in a gelatinous matrix. The cells are usually
connected to each other by strands of cytoplasm. In structure, each single cell
resembles Chlamydomonas
in having two flagella and a single cup-shaped chloroplast. This footage
focuses down and back up through a colony. At first the focus is on the colony
wall, then it moves through four daughter colonies inside. The first is smaller
and younger, the larger three are older. All colonies have arisen from certain
enlarged cells in the colony which are destined to divide to form daughter colonies.
Credit: Michael
Clayton, University of Wisconsin, Madison
Volvox Daughter - VolvoxDaughter-S.mov
Seen in this footage is the release of a
daughter colony of Volvox
from its parent colony. When the parent colony was in its juvenile stage, it
contained 16 large asexual reproductive cells called gonidia. While the parent
colony expanded, each of these gonidia underwent 11-12 rapid divisions to form
a new set of 16 juvenile colonies within the parent, one of which is being
released here. In this juvenile daughter colony, 16 gonidia are already
present, having formed during the 11-12 rapid divisions.
Credit:
Michael Clayton, University of Wisconsin, Madison
Volvox Flagella
- VolvoxFlagella-S.mov
This video clip
focuses through a Volvox
colony at 600x magnification, and back. At first, the focus is on the outer
wall closest to the viewer, then it moves through a daughter colony inside to
the back side of the mother colony. Finally, the focus comes back up, ending
midway through the daughter colony, with the flagella of the wall cells in the
daughter colony clearly visible. The structure of each cell and their
cytoplasmic connections are seen even more clearly in this higher magnification
view than in the previous two clips.
Credit:
Michael Clayton, University of Wisconsin, Madison
Vorticella Cilia - VorticellaCilia-S.mov
Vorticella is a member of the ciliated protists,
but the body has few cilia. Surrounding the “mouth” are three rows
of cilia that wind in counter-clockwise direction toward the mouth. The
bell-shaped body normally remains attached to the substrate by a coiled stalk
that is able to contract and extend itself while the organism searches for
food. The video shows how the beating cilia sets up a distinctive
counter-clockwise current that draws food particles to the mouth of the cell.
Ingestion is by phagocytosis.
Credit: Courtesy
of Graham R. Kent and Rebecca L. Turner, Smith College
Vorticella Detail - VorticellaDetail-S.mov
This clip shows the ciliated protist Vorticella. This species is a suspension feeder,
with bands of ciliary membranes surrounding the apical end (shown here at the
right). Movement of these membranes serves to create water currents and sweep
food particles, such as bacterial cells, into the buccal cavity and from there
into the forming food vacuole. This particular species has a bell-shaped body
on a long slender stalk. Within the body covering of the stalk lie bundles of
contractile filaments called myonemes. Contraction of the myonemes results in
the popping motion shown here.
Credit: Michael Clayton, University of
Wisconsin, Madison
Vorticella Habitat - VorticellaHabitat-S.mov
This clip shows the ciliated protist Vorticella. As seen here, the organism is sessile,
with its bell-shaped body anchored to a piece of algae by a long slender stalk.
Within the body covering of the stalk lie bundles of contractile filaments
called myonemes. Contraction of the myonemes results in the popping motion
shown here.
Credit: Michael
Clayton, University of Wisconsin, Madison