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LESSON 7- 2 (pages 239-243)
Bacteria in Nature
A. Beneficial Bacteria
 Many organisms, including humans, depend on bacteria to survive.
 Bacteria living inside the intestines of humans and other animals help digest food, make
vitamin K, and prevent harmful bacteria from growing.
 _Decomposition, the breaking down of dead organisms and organic waste, is an important
process in nature.
 __Nitrogen Fixation__ is the conversion of atmospheric nitrogen into nitrogen compounds
that living things can use.
 __Bioremediation__ uses organisms, such as bacteria, to clean up environmental pollution.
These organisms break down harmful substances, such as sewage, into less harmful
materials that can be used as landfill or
fertilizers
.
 __Bacteria_____ are used to make foods such as pickles, yogurt, cheeses, buttermilk,
vinegar, and soy sauce.
B. Harmful Bacteria
 Some bacteria are called pathogens—agents that cause disease.
a. Some pathogens that normally live in the body cause illness only when the person’s
immune system is weakened.
b. Some pathogens can enter the body through a cut, in air, or on food you eat.
c. After they are inside the body, they can __reproduce
and cause disease.
d. Some bacteria make people sick by damaging tissue.
e. Some bacteria cause illness by releasing toxins.

_Antibiotics_ are medicines that stop the growth and reproduction of bacteria.
 Bacteria can become resistant to antibiotics.
a. Random mutations to a bacterium’s DNA enable it to survive a specific antibiotic.
b. Only the bacteria with the mutation survive; they reproduce and become more common.
 __Pasteurization__ heats food to a temperature that kills most harmful bacteria.