This golden algae is swimming around in water
and white light, illuminated from below using a brightfield microscope. And here we have that mallomonas sample, filmed
a day later using a different technique thanks to a brand new, freshly installed microscope. When James, our master of microscopes, saw
them for the first time, he got a little emotional because, to quote him directly, “the thing
I know so well, was looking so so much different than usual.” Those differences in how the mallomonas look
are due to a type of microscopy called “Differential Interference Contrast.” Or…DIC. Earlier this year, James started a crowdfunding
campaign to purchase a new microscope, one that would allow him to use differential interference
contrast to produce these images you are seeing now. Now technically, “differential interference
contrast” is not a type of microscope. Rather, it’s a method that enhances contrast. And as you can see, the final product is an
image that seems almost 3-dimensional. Just watch this stentor coeruleus as it swims
across the slide. Its cilia are so prominent that it almost
feels like you can touch their vibrating fuzziness. And the striations down its body are so sharp
that when the stentor contracts, it’s like you can feel it pushing inward and then back
out again. Differential interference contrast microscopy
was invented by Georges Nomarski in 1952, building off the principles underlying phase
contrast microscopy, which is a different though similar thing. But both of these methods work to translate
invisible shifts in light phase that can happen when studying certain samples into visible
changes in light amplitude, which we see as changes in light intensity. And as a result, both techniques enhance contrast
and let us see parts of the microcosmos that might be invisible with regular brightfield
microscopy. But phase contrast microscopy and DIC shift
and work with light in different ways to accomplish this goal. How do they do it? Well, if you’ve ever taken an optics course,
you will remember how terrible that was. But, very basically, phase contrast and DIC
are two ways to take advantage of a strange reality. Light actually travels further through some
materials than others. Kinda. The optical path length is a function of both
the distance between two points and the refractive index of the material the light is travelling
through. Basically, denser samples have longer optical
path lengths. Phase contrast microscopy takes advantage
of that, making areas with longer optical path lengths look darker. DIC on the other hand, doesn’t make areas
that are denser darker, it uses some very cool optics to create sharp contrast in areas
of rapid change in the optical path length. So, the faster the gradient from more to less dense or vice versa, the more contrast you see. But it’s also important to note that while
these images are the result of light traveling through a sample, they are not an actual topographical
map of an organism. DIC microscopy is a technique, but it does
require certain physical additions to a microscope. For one thing, we need to split light apart. So, first we have a prism that splits polarized
light into two orthogonal rays of light that will then pass through the sample and interact
with it in different ways. And then there’s a second prism that recombines
those two rays after they’ve traveled through the sample, forming an image based on the
differences those two beams of light experienced for our eyes and cameras to see. In addition to these prisms, this technique
relies on having higher quality objectives than what we’ve been using in the past. The objectives are the little lenses at the
bottom of the microscope that actually do most of the magnification. Not many people would realize this, but the
objectives we use for Journey to the Microcosmos are some of the cheapest and most common types
of objectives, they’re known as achromatic objectives. But while these objectives produce so many
of our favorite images, James needed a microscope update to be able to do differential interference
contrast. So with help, perhaps including some from
you, James bought a new Zeiss microscope. It took eight weeks for it to arrive, which
is a long time to wait. But luckily the manufacturers sent him a 150
page manual to occupy his time until it arrived. When the microscope finally showed up, James
still had to wait for an engineer to install the nearly 50 pound machine. But he didn’t waste any time. James went out to gather his precious Mallomonas
and prepared a slide that night, keeping it stored in a humidity chamber so that he could
look at it as soon as the microscope was ready. The next day, the Zeiss engineer took 3.5
hours to put all the pieces together and set everything up. But from there, well, it was all on James
to observe what he could and experiment with his new microscope. Some of his experimenting has been geared
towards making sure that he can get the best image possible. These objectives have a much smaller working
distance compared to our previous ones, and so you need to prepare the slides a lot thinner
to get a sharper image. So even for our master of microscopes, there
was somewhat of a learning curve to make sure he was getting videos that were as sharp and
vivid as he wanted. But some of the experimenting is based out
of that most exciting thing of all: curiosity. He’s removed some of the prisms to see how
it affects the footage, and added a magnifying glass over the light source to scatter the
light in different ways. That’s the joy of the microcosmos. It is so infinite. There’s it’s own objective existence,
full of so many more organisms than we’ll ever be able to identify. But there’s also the infinite nature of
how we experience it, of how our own view of this world is shaped by the many different
tools we use to observe it. And maybe that’s the case all the time...that
what we see is as much about how we view the world as it is about the world itself. The same thing with a different lens, a different
technique, a different base of knowledge, can look completely different. As we start our third season of Journey to
the Microcosmos, we hope you will continue to join us through both our new and old lenses,
as we uncover more of this hidden, unending world. Thanks for coming with me on this journey
as we explore the unseen world that surrounds us. And guess what, we have new merchandise! We have algae socks We also have a new coloring book so you can
spend a little time with your favorite microbes relaxing, zoning out, letting yourself just
be for a little while. Thank you of course to all of these people
on the screen right now. They are our patrons on Patreon. These folks are what make this channel possible. If you’d like to join them in supporting
us, check us out at patreon.com/journeytomicro. If you want to see more from our Master of
Microscopes James Weiss, you can check out Jam & Germs on Instagram where you can see
more great stuff from his new microscope. And if you want to see more from us, there
is always a subscribe button somewhere nearby.
