the body by ingestion, skin contact, and inhalation. An endosporeis a bacterium
in a dormant state that forms within a cell.
Fortunately, incidents of biological attacks using microorganisms have been
infrequent. However, there are thousands of microorganisms all around us that
can be just as deadly and debilitating as the microorganisms used in warfare
throughout history.Types of Microorganisms
UNFRIENDLY MICROORGANISMS
An infection is caused by the infiltration of a disease-causing microorganism
known as a pathogenic microorganism. Some pathogenic microorganisms infect
humans, but not other animals and plants. Some pathogenic microorganisms that
infect animals or plants also infect humans.
Pathogenic microorganisms make headlines and play an important role in his-
tory. Legendary gunfighter John “Doc” Holliday is famous for his escapades in
the Wild West. He dodged countless bullets, showing that he was the best of the
best when it came to gun fighting. Yet Mycobacterium tuberculosistook down
Doc Holliday quietly, without firing a shot. Mycobacterium tuberculosisis the
bacterium that causes tuberculosis (Fig. 1-1). This bacterium affects the lung tis-
sue when droplets of respiratory secretions or particles of dry sputum from a per-
son who is infected with the disease are inhaled by an uninfected person.(^2) CHAPTER 1 The World of the Microorganism
Fig. 1-1. Mycobacterium tuberculosisis the bac-
terium that causes tuberculosis.