We have just completed a reasonably extensive survey of bacterial and viral pathogenic species,
and with that we should be starting to get a more comprehensive picture of infectious
diseases as a whole.
But now it’s time to switch gears and dig into some more general microbiology concepts,
so that we can get a broader understanding of this topic, and we are going to start by
examining the indispensable tool of the microbiologist, the microscope.
As we learned at the very beginning of this series, microbiology is the study of microscopic
organisms, and to study this otherwise invisible world, microbiologists use microscopes.
This tool allows scientists to observe microscopic tissue and organisms with magnification ranging
from 1,200 to 1,000,000 times larger than its original size.
But how exactly did we get from examining a specimen simply by pulling it very close
to our faces, to being able to look at a screen of a sample enlarged enough to study the details
of proteins within a single cell?
Some of this information was outlined in the introduction to this series, but let’s get
a more sophisticated version of that story now.
To begin this tale, we have to go back in time a few millennia.
The very first signs of crude magnification tools appeared in about 710 BCE with the Nimrud
Lens, which was no more than a crystal that people would use as a magnifying glass.
This was found in Nimrud, now modern day Iraq.
Later on in history, reading stones and eye glasses were also used to enhance the eyesight
of individuals.
Now let’s fast forward to 1595 CE, when the invention of the first compound microscope,
or microscope with two or more lenses, was invented.
The invention was attributed to Zacharias Janssen, although the records show that he
would have been in his teens at this time, so there is speculation that his father, Hans
Janssen helped him with this invention since they both worked as spectacle makers in Holland.
Before this microscope, the smallest object people could visualize was the width of a
human hair, which might seem small, but is actually quite large compared to the microbial
world.
Janssen's microscope allowed for the visualization of objects nine times their original size.
Early advances in microscopy after the invention of the first compound microscope revolved
around the aim of producing better resolution, as improving magnification was not as tricky.
Resolution is the ability to distinguish between two objects as separate entities, as opposed
to the objects appearing smudged together.
For example, currently the best resolution of a light microscope is 0.25 micrometers,
which means that two objects can be a quarter of a micrometer away from each other without
blurring together.
As a point of reference, 1,000 micrometers make up one millimeter, which are the smallest
lines on a standard ruler.
After the invention of the compound microscope, the next big development in microscopy was
brought about by a Dutch merchant, Antonie Van Leeuwenhoek, who made the first microscope
that could visualize an individual cell.
Leeuwenhoek made over 500 prototypes to get to the final version of his microscope, which
could visualize objects 200 times their original size, a significant improvement from Janssen’s
microscope.
This development led to Leeuwenhoek’s discovery of bacteria, protists, sperm cells, and much
more, as we discussed when we referenced his animalcules in the introduction to this series.
At this point in time the world of microorganisms was unlocked and available for study, but
the look and accessories of the compound microscope were still far from what we recognize as a
microscope today.
It wasn’t until 1665 that Robert Hooke, a scientist from the United Kingdom, added
features to the microscope like the stage to hold the specimen, the illuminator to shine
light on the specimen, as well as focus controls.
These accessories allowed scientists to have more control over how they view the specimen.
Additionally, these accessories made using the microscope much simpler, such that individuals
would require very little training to operate it.
The major innovations that were to follow didn’t arrive until the 20th century, but
each was truly significant.
First there was the evolution of the microscope from the Light or Optic Microscope to the
Phase Contrast Microscope in 1930.
Then, the Transmission Electron Microscope in 1931, followed by the Scanning Electron
Microscope in 1942.
Finally, in the latter half of the century came the Confocal Microscope in 1978, and
the Scanning Tunneling Microscope in 1981.
Advancements in microscopy are still being made to this day, so there is no telling what
is around the corner.
But over the next few tutorials we are going to go into more detail regarding the functions
and applications of some of the types we just mentioned, which remain the most used techniques
in microscopy today.
So without any delay, let’s move forward and learn more about microscopy.