1

CHAPTER

1

The World of the

Microorganism

Microbiologyis the study of microorganisms, which are tiny organisms that
live around us and inside our body. An organismis a living thing that ingests and
breaks down food for energy and nutrients, excretes undigested food as waste,
and is capable of reproduction. You are an organism and so are dogs, cats,
insects, and other creatures that you see daily.
A microorganism is simply a very, very small organism that you cannot see
with your naked eye, but you sure feel its effect whenever your eyes fill with
water and mucus flows like an open faucet from your nose. You call it a head
cold. Actually, you are under siege by an army of microorganisms attacking
membranes inside your body. Watery eyes and a runny nose are ways that you
fight microorganisms by flushing them out of your body.
Microorganisms are a key component of biological warfare along with chem-
icals that disrupt homeostasis. The anthrax attack that followed the 9/11 terror-
ist attacks clearly illustrated how a dusting of anthrax in an envelope can be
lethal to people in an office building. Anthraxis a disease caused by the micro-
organism Bacillus anthracis, a bacterium that forms endospores and infiltrates

Copyright © 2005 by The McGraw-Hill Companies, Inc. Click here for terms of use.