BACKGROUND INFORMATION for LAB EXERCISE #2
What is the difference between genetic diseases, diseases of aging, and infectious diseases?
Today’s lab examines microbes (
bacterial, fungal, protozoan
), “good” or “bad”. Although humans
have long observed the devastating effects of infectious diseases, the microscope made it possible to see the
“bad microbes,” known as germs or pathogens. Researchers use
to identify infectious agents
in disease (see Lab 1). When infectious organisms are smaller than can be seen by the naked eye, they are
referred to as “
The term "
" refers to conditions that impair normal tissue function. For example, cystic fibrosis,
atherosclerosis, and measles are all considered diseases. However, there are fundamentally different causes for
each of these diseases.
Cystic fibrosis (CF) is due to a specific genotype that results in impaired transport of chloride ions across cell
membranes, leading to the production of abnormally thick mucus. Thus, CF is most accurately called a
, one that would be inherited from one’s parents. Atherosclerosis, which can lead to heart attacks and
strokes, may be considered a
disease of aging
, because it typically becomes a problem later in life after plaques
of cholesterol have built up and partially blocked arteries.
In contrast, measles is an
because it occurs when an individual contracts an outside agent, the
measles virus. An infectious disease is a disease that is caused by the invasion of a host by agents whose
activities harm the host's tissues (that is, they cause disease) and can be transmitted to other individuals (that is,
they are infectious).
HISTORY AND CLASSIFICATION OF MICROBES
What are microbes and how did we know that
was a microbe?
Last week, you had a chance to make observations about a microbe called
saw how this infectious agent caused a disease in potatoes known as “
You determined it was the
causal agent using Koch’s Postulates.
But, were you certain at the time whether this causal agent was a
bacteria, fungus, virus, of protozoa.
It wasn’t until the invention of the microscope around 1590 that scientists
were even able to see the world of microbes.
But, once they were, then there was a need to understand more
Using information from last week’s lab, compare the dates of the invention of the microscope and the
work of Koch.
What other progress was made in the world of science between these two dates?
were scientists doing?
1590, two Dutch eye glass makers, Zaccharias Janssen and son Hans Janssen experimented with
multiple lenses placed in a tube. The Janssens observed that objects viewed in front of the tube appeared greatly
enlarged, creating both the forerunner of the compound microscope and the telescope.
1665 – English physicist, Robert Hooke looked at a sliver of cork through a microscope lens and noticed