Download Bacteria Prokaryotes Eubacteria Archaebacteria

18.1 Bacteria
Bacteria
Section 18.1
Prokaryotes
· includes Bacteria (eubacteria) and Archaea
· most abundant type of organism
· evolution has yielded hundreds of thousands of
bacteria that are adapted to places no other
organisms can live
Eubacteria
Gram positive (purple)
Examples:
Staphylococcus,
Streptococcus,
Clostridium tetani,
Clostridium botulism
· 3 common shapes
baccili - rods
spirilla - spirals
cocci - spherical
· strong cell walls that contain
peptidoglycans (mesh of sugars and
amino acids)
· Gram stain - important for diagnosing infection
red (neg) - thin peptidoglycan layer
purple (pos) - thick peptidoglycan layer
· some are photosynthetic
1 What shape are these bacteria?
Gram negative (red)
Examples: Salmonella,
E. coli, Pseudomonas,
Enterobacter
Archaebacteria
A
bacilli
· live in extreme environments
· themoacidophiles - love hot (above 80 C) and
acidic (pH 1-2) environments
B
cocci
· methanogens - use CO2 to create methane gas
C
spirilli
· halophiles - love very salty environments
D
spherical
anaerobes - die in presence of oxygen
anaerobes
aerobics (need oxygen) and photosynthetic
· not affected by medication used to treat bacterial
infections
· as much in common with eukaryotes as with
bacteria
18.1 Bacteria
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Typical Structure
microscopic
unicellular
lack membrane-bound organelles
some surrounded by a capsule
protective polysaccharide coat
secreted by the bacteria
· cell wall
· cell membrane - lipid layer
· cytoplasm - contains ribosomes that are used for
protein synthesis
· pili - short hair-like projections that help bacterium stick
to host cell
· plasmid - circular ring of DNA
· nucleoid - DNA
· flagellum - help bacteria move
3 What is structure "B"?
A
cytoplasm
B
capsule
C
cell wall
D
cell membrane
2 What is structure "E"?
A
plasmid
B
nucleoid
C
capsule
D
cytoplasm
Reproduction
· reproduce by binary fission
divide in half (asexual)
like mitosis
· conjugation - protein
bridge forms between two
or more bacterial cell so
they can exchange DNA
increases genetic diversity
· heterotrophs
Metabolism
saprobes - obtain energy by decomposing organic
molecules
· photoautotrophs
photosynthetic cyanobacteria
· chemoautotrophs
Survival
· endospore - thick protective wall around DNA
forms in harsh environmental conditions
bacterial cell might die, but the endospore (w/DNA)
will survive
· mutations - frequent changes allow bacteria to
survive and thrive
chemosynthesis - nitrogen and sulfur
· aerobes and anaerobes
obligate aerobes - require oxygen to grow
obligate anaerobes - die in the presence of oxygen,
use fermentation
facultative anaerobes - can use oxygen or
fermentation
endospore
18.1 Bacteria
4 Which type of bacteria are likely to
form endospores around their genetic
material?
A
Eubacteria
B
Archaea
C
Cocci
D
Baccilli
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Ecology of Bacteria
most bacteria are harmless and helpful
recycle nutrients (decomposers)
help fertilize fields (nitrogen fixation)
normal flora
bacteria that live in and on us
protect the body and provide essential nutrients
· produce foods and medicines
· disease-causing bacteria
invade tissues and reproduce rapidly
produce toxins