discovered that leukocytes (white blood cells) defended the body by engulfing
and eating the invading microorganism.DRUGS: SEND IN THE CAVALRY
Invading microorganisms activate your body’s immune system. It is at this point
when you experience a fever and feel sick. In an effort to help your immune sys-
tem, physicians prescribe drugs called antibiotics that contain one or more
antimicrobial agents that combat bacteria. An antimicrobial agent is a substance
that specifically inhibits and destroys the attacking microorganism.
One of the most commonly used antimicrobial agent is penicillin. Penicillin
is made from Penicillium, which is a mold that secretes materials that interfere
with the synthesis of the cell walls of bacteria causing “lysis,” or destruction of
the cell wall, and kills the invading microorganism.IMMUNITY: PREVENT ING A MICROORGANISM AT TACK
Our bodies have a wide range of body responses in the fight against pathogens.
These responses are referred to as nonspecific resistance. Resistanceis the abil-
ity of the body to ward off disease. The lack of resistance is called susceptibil-
ity. When your immune system is compromised you become susceptible to
pathogens invading your body where they divide into colonies causing disease,
making you sick.
Generally, your first line of defense is to use mechanical and chemical means
to prevent a pathogen from entering your body. Skin is the primary mechanical
means to fight pathogens; it acts as a barrier between the pathogen and the inter-
nal structures of your body. Mucous membranes are another mechanical barrier;(^8) CHAPTER 1 The World of the Microorganism
Unit Fraction of Standard English Equivalent
meter (m) 3.28 feet
centimeter (cm) 0.01 m = 10−^2 0.39 inch
millimeter (mm) 0.001 m = 10−^3 0.039 inch
micrometer (μm) 0.000001 m = 10−^6 0.000039 inch
nanometer (nm) 0.000000001 m = 10−^9 0.000000039 inch
Table 1-1. Quantity and Length: Metric and English Equivalents