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Chapter 20
Section 1
Bacteria
Two Types of Bacteria
• There are two major groups of
bacteria
–Domain Archae
–Domain Bacteria
Archeabacteria
• Older than eubacteria
• Contain unusual lipids in cell wall and introns in
their DNA- both are lacking in eubacteria
• Known for living in extreme conditions
– Examples:
• Methanogens: anaerobes that make energy by converting H2 and
CO2 into methane gas
• Extreme halophiles: thrive in environments w/high salt content.
They use salt to make ATP
• Thermoacidophiles: live in highly acidic, hot environments.
Eubacteria
• Most known prokaryotes are members of the
Domain Bacteria.
• Found everywhere
• Occur in three shapes
– Cocci (pl) Coccus (sing) are spherical or round in
shape
– Bacilli (pl) Bacillus (sing) are rod shaped
– Spirilli (pl) Spirillus (sing) are cork screw shaped
The Gram Stain
• Bacteria are classified partly due to the way that
they react to a Gram Stain
– Gram positive bacteria dye purple (they have a thick
layer of peptidoglycan and no outer membrane)
– Gram negative bacteria dye pink/red (they have a thin
layer of peptidoglycan and have an outer membrane)
– Gram positive bacteria and Gram negative bacteria
differ in their cell wall structure. This difference
impacts which stain they will absorb.
Obtaining Energy
• Some bacteria are:
– Photoautotrophic: use light to make energy,
photosynthetic
• Ex. Sulfur and nonsulfur bacteria and cyanobacteria
– Chemoautotrophs: get there energy from inorganic
sources
– Heterotrophs: get there energy from other organisms.
Heterotrophs can be broken down into:
• Anaerobic: do not need oxygen to survive
• Obligate anaerobes: will die if exposed to oxygen ex.
methanogens
• Obligate aerobes: require oxygen to survive ex. Tubercullosis
(TB)
• Facultative anaerobes: live w/ or w/o oxygen ex. E. coli
Prokaryote Reproduction
• Reproduce through binary fission
– Exchange of genetic material through
conjugation, transformation, and transduction;
and survive harsh conditions by forming
endospores
Types of Genetic Recombination
Reproduction
1.
Transformation: In transformation a bacterial cell will
take up free floating genetic material from the
surrounding environment.
Conjugation: one bacteria shares genes contained in
a plasmid with another bacteria through a pilus (sing)
pili (pl)
Transduction: a virus takes up a piece of a host
bacteria’s DNA during infection
2.
3.
–
–
–
When new viruses form they have the piece of bacterial DNA in
their DNA
When the new viruses infect another DNA they will insert their
new DNA along with the piece of bacterial DNA into the host
bacteria
Transduction occurs during the lysogenic and lytic cycle of
virus reproduction
Bacteria Toxins
Two Types:
1. Endotoxins: are composed of lipids and
carbohydrates. They are part of the cell
membrane of Gram negative bacteria. They
are released when the bacteria dies
Ex. E. coli causes illness through endotoxins
2. Exotoxins: are proteins produced by Gram
positive bacteria
Ex. Diptheria causes illness by releasing
exotoxins
Ex. Botulism causes illness by releasing
exotoxins
Disease
• Bacteria cause illness through toxins
(endotoxins and exotoxins) and enzymes
• Digestive enzymes are released by
bacteria to open up tissue to further
invasion
Ex. Streptococci (strep throat) releases
enzymes that destroy blood clots
How do antibiotics work?
• Antibiotics are chemicals that kill bacteria
by interfering with their life functions
(Table 24-5)
– Penicillin inhibits cell wall synthesis
– Rifampin interferes with RNA synthesis
Bacterial Resistance
There are two main causes:
• Antibiotics are prescribed for viral
diseases
• Anitibiotics are not used properly
Some bacteria possess a genetic mutation
that renders them less susceptible to the
antibiotics. These bacteria are said to be
antibiotic resistant.
Good or Bad?
• Not all bacteria are bad
– Some plants contain bacteria in their roots
that fix nitrogen.
• Legumes such as soy and peanuts have this ability
– Bacteria are important in the process of decay
– Bacteria play a necessary role in the creation
of some food Ex. Yogurt, buttermilk,
sauerkraut
Bacteria vs. Viruses
• Bacteria are:
– Living organisms
– Capable of making or obtaining energy
– Completely different in structure
• Viruses are:
– Not living organisms
– Not capable of making or obtaining energy
(they don’t need to)
– Completely different in structure