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Chapter 7
Bacteria
What are bacteria?
• Bacteria are microscopic, living cells.
– live almost everywhere, even extreme
environments
– sphere-shaped, rod-shaped, spiral-shaped
• smaller than plant or animal cells
• prokaryotic-no membrane-bound internal
structures
What are bacteria?
– some have a capsule around the cell wall
while others have an outer slime layer
– many have whiplike tails called flagella
– most reproduce by fission
What are bacteria?
– can be producers or consumers
• most are aerobes
• some are anaerobes
What are bacteria?
• Bacteria are classified into two
kingdoms.
– Eubacteria larger of the two bacteria kingdoms
• consumer eubacteria are grouped by cell wall
thickness
• cyanobacteria produce their own food and are
commonly called blue-green bacteria
• cyanobacteria provide food and oxygen for
aquatic life
– bloom- may be harmful
What are bacteria?
• Bacteria are classified into two
kingdoms.
– Archaebacteria
• kingdom bacteria are often found in extreme locations
and divided into groups based on where they live or how
they get energy
– some live in salty, acidic, or very hot environments
– one anaerobic group produces methane gas
Bacteria in Your Life
• Most bacteria are helpful rather than
harmful
– necessary for human health
• many aid digestion and some produce vitamins
• some produce antibiotics
Bacteria in Your Life
• Bacteria help keep nature in balance
– bacterial saprophytes use dead organisms
as food and energy sources
– nitrogen-fixing bacteria in the soil and
plant roots change nitrogen from the air to
a form that plants and animals can use
Bacteria in Your Life
• Bacteria can be used to clean up the
environmental pollution through
bioremediation
– some bacteria break waste down into
harmless compounds
– certain bacteria can eat pollutants
Bacteria in Your Life
• Many foods are made using bacteria
– used in dairy products
– sauerkraut and pickles are also among foods
made with bacterial help
Bacteria in Your Life
• Bacteria are used in industry
– bioreactors- large, carefully controlled
containers used to make medicines and
many other products
– methane-producing bacteria can digest
waste and provide a source of fuel
Bacteria in Your Life
• Bacteria that cause disease are called
bacterial pathogens
– toxins are made by some bacterial
pathogens
– some form thick walled structures called
endospores when environmental conditions
are unfavorable
Bacteria in Your Life
– pasteurization- process of limited heating,
can kill most harmful bacteria in food
– vaccines can prevent some bacterial
infections
• made from damaged or dead bacterial cells
• enable white blood cells in the body to
recognize a particular type of bacteria and
attack it if it appears at a later time