Download Chapter 23 Bacteria Prokaryotes are single celled organisms that do

Chapter 23
Bacteria
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Prokaryotes are single celled organisms that do not have a membrane bound nucleus.
Domain Archaea
o They differ from bacteria in the make up of their cell walls, membrane lipids,
genetics, and metabolism.
o Archaea were first discovered in extreme environments such as swamps, salt
lakes, and hot springs.
Archaeal Groups
o Methanogens
 They convert hydrogen gas and carbon dioxide into methane gas for
energy
 Oxygen is poisonous to them so the are anaerobic and found in deep
fresh water, marine mud, swamp mud, and sewage
 They are found living in the stomachs of cows and termites
o Halophiles
 Are found in very high salt concentrations such as The Great Salt Lake and
The Dead Sea
o Thermoacidophiles
 Live in very acidic environments that have very high temperatures such as
hot springs
 They can also be found on the ground near volcanic vents and in the
oceans near hydrothermal vents called black smokers
Domain Bacteria
o Most known prokaryotes are bacteria. They occur in many shapes and sizes.
 Bacilli are rod shapes bacteria
 Cocci are sphere shaped bacteria
 Spirilla are spiral shaped bacteria
 Streptococci are chains of cocci
 Staphylococci are grapelike clusters of cocci
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Important bacterial groups
o Proteobacteria are both aerobic and anaerobic
 Rhizobium are nitrogen fixing bacteria and are found in the roots of
legumes, which include peas, beans, alfalfa, and clover. They fix
atmospheric nitrogen into ammonia which plants can use.
 Some species of proteobacteria are enteric, they live in human and
animal intestines.
 E.coli makes vitamin K and help digestive enzymes with
breakdown of food.
 Some E. coli and species of Salmonella can cause foodborne
illnesses
o Gram Positive Bacteria
 Streptococcus bacteria causes strep throat
 Clostridium botulinum causes botulism, they release toxins into the
environment
 Lactobacilli turns milk sour and makes yogurt
 Bacillus anthracis makes the biological weapon anthrax
 Actinmyocetes are a form of bacteria that make antibiotics
o Cyanobacteria make their own food through photosynthesis but are not plants.
They lack a nucleus and membrane bound organelles. They are believed to be
the first oxygen producing organism on Earth and responsible for putting oxygen
into our atmosphere
o Spirochetes are responsible for the STI syphilis and for Lyme disease
o Chlamydia another STI
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Biology of Prokaryotes
o Structure and Function
 Cell Wall is made of peptidoglycan instead of cellulose
 Cell membrane regulates what enters and leaves the cell
 The cell membranes of photosynthetic bacteria contain thylakoids which
contain pigments
 DNA is a single closed loop attached at one point to the cell membrane, it
is not enclosed in a nucleus
 Capsule is an outer covering of polysaccharides that bind to the cell wall
protecting it from dry harsh conditions
 Pili are short hair like projections on the surface of a bacterium that allow
it to attach to other bacteria and to host cells
 Endospores can form in some bacteria that are in unfavorable conditions.
They surround and protect the DNA until conditions are right. They can
stay in this state for years.
 Flagella are long hair like projections that help the bacterium move. They
whip back and forth. Movement is called taxis.
 Some bacteria release a slime layer and move through it.
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Pathology is the scientific study of disease.
Bacteria and other organisms that cause disease are called pathogens.
Some bacteria cause disease by making certain poisons called toxins.
o Exotoxins - Toxic substances that bacteria secrete into their environment.
Example: Tetanus is caused by the bacteria Clostridium tetani
o Endotoxins- Toxic substances that are not released until the cell dies. They can
cause fever, body aches, diarrhea, hemorrhage, and weakness.
Antibiotics affect bacteria by interfering with certain cellular activity.
o Penicillin blocks the ability to build new cell walls
o Tetracycline blocks protein synthesis
Antibiotics are made naturally by some fungi and bacteria.
Antibiotic resistance is a major problem. Mutations have allowed bacteria to become
resistant to some antibiotics. Some bacteria now have resistance genes that protect the
bacteria from antibiotics.