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Study Guide – Bacteria (Eubacteria) and Archaea (Archaebacteria)
I. Bacteria
A. General characteristics –
1. unicellular
2. prokaryotes – lack a nucleus and most organelles
3. made of two different domains, Bacteria and Archaea
4. first life forms to appear on earth, 3.8 billion years ago
5. most numerous of all organisms on earth, and live in every
environment
6. bacteria come in many shapes and colors
a. sphere – cocci
b. rod – bacilli
c. spiral – spirilla
7. bacteria live alone and in colonies
B. Basic structure –
1. Cell wall – tough, rigid structure that supports, shapes and protects
2. Capsule – protects the bacterium and makes it sticky
3. Flagella – whip-like tail for movement
4. Cilia – tiny hair-like projections that help movement
C. Life functions –
1. aerobic respiration – uses oxygen
2. anaerobic respiration – uses a gas other than oxygen
3. autotrophs – make their own food
4. heterotrophs – eat others
5. decomposers – break down dead, decaying organic matter
(saprophytes)
6. binary fission – bacteria divide in two to reproduce asexually
7. endospore – “resting cell” protects the bacterium from freezing,
chemicals, heat, radiation, etc…for 100s of years.
8. symbiosis – when two organisms live in an intimate relationship
(constantly touching), where at least one benefits.
a. mutualism – both symbionts benefit
i. nitrogen fixing bacteria – live on the roots of plants
Nitrogen fixing bacteria live on the roots of plants.
Bacteria get a place to live and are protected from drying out and from other
organisms.
Plants get the nitrogen from the bacteria, which acts as fertilizer.
80% of the air is nitrogen. Nitrogen is inert (it does not react with other chemicals).
Nitrogen fixing bacteria are the only organisms on earth that can naturally take
nitrogen out of the air, and put it into a solid form.
Peas, beans, and clover have a lot of nitrogen fixing bacteria on their roots. Nodules
of the bacteria can be seen on the roots (see p197).
ii. bacteria in humans help to produce vitamins
iii. bacteria in the rumens of cows digest cellulose
b. parasitism – one symbiont benefits, the other is harmed
i. illness/sickness caused by bacterial infection
D. How bacteria affect us
1. oxygen producing – bacteria changed the earths atmosphere from 0%
oxygen to over 20% oxygen during the two billion years they
dominated the planet, this paved the way for more complex life
2. food – high fructose corn syrup, cheese, butter, yogurt, sour cream,
pickles, soy sauce, vinegar, grow crops (nitrogen fixing bacteria), and
cyanobacteria is eaten
3. fuel –
a. methane from garbage, decaying plants, sewage
b. petroleum – “oil,” comes from the remains of bacteria that lived
billions of years ago
4. environmental clean-up – break down oil spills, toxic chemicals, even
nuclear waste
5. medicine –
a. antibiotics – chemicals that bacteria produce that kill other
bacteria, many antibiotics destroy the cell wall of bacteria
b. bacterial infections include – strep throat, some pneumonias,
diptheria, cholera, tetanus, tuberculosis, bubonic plague, Lyme
disease, tooth decay and gum disease
6. bacteria can be used to make food coloring, cosmetics, enzymes (for
chemical reactions)
7. many bacteria cause food to spoil and can cause food poisoning
E. Two Domains –
1. Bacteria
b. grouped by shape and structure, how they obtain food, what
eat, wastes produced, methods of movement, and whether
aerobic or anaerobic
c. cyanobacteria – autotrophs
i. produce oxygen
ii. are blue/green in color, can be yellow, black or red
iii. some cultures eat cyanobacteria
iv. cyanobacteria is at the bottom of most food chains
d. eutrification –
When too many nutrients (fertilizers and organic matter) are introduced into
waterways (ponds, lakes, rivers, oceans), cyanobacteria can grow out of control
“bloom.”
Blooms look like a mat of green slime on the surface of the water.
Blooms use up all available resources, and then die, sinking to the bottom of the
water.
Decomposers eat up the dead cyanobacteria “bloom,” and use up all the oxygen in
the water. All life forms dependent on oxygen die, and we get a “dead zone.”
e. heterotrophic bacteria are classified by cell wall thickness and
shape
2. Archaea – extremophiles
A. live in extreme environments – salt, heat, cold, dry, acidic,
basic, chemical (sulfur)