Post on 27-Apr-2019
Bacteria
Bacteria General Information
• Prokaryotes- (no membrane bound
organelles), contain ribosomes
• Unicellular
• Found Everywhere
• 2 Kingdoms:
Archaebacteria & Eubacteria
Archaebacteria
• Archaebacteria (4 types) – live in
extreme habitats
– unusual lipids in their membranes
– no peptidoglycan, unique
polysaccharides
– introns in their DNA
– unique cell membrane
composition
Euryarchaota
1. Methanogens 2. Halophiles
3. Thermoacidophiles
Crenarchaeota
4. Hyperthermophiles
1
2
3
4
Euryarchaota
1. Methanogens - O2 free and produce
methane
Ex: marshes; digestive tracts of
mammals; sewage treatment plants
2. Extreme Halophiles - high salt
concentrations
Ex: Great Salt Lake and Dead Sea
3. Thermoacidophiles - hot, acidic sulfur
springs
Ex: hot springs
Bacterial Structure
Bacterial Structure Composed Of:
• cell wall containing peptidoglycan
• a cell membrane
• cytoplasm
• a single circular piece of DNA located in a region
called the nucleoid
• ribosomes
• sometimes plasmids
– Plasmids – smaller circular pieces of DNA
• some are covered by pili, hairlike projections
• some are covered by glycocalyx, sticky sugars
– Loose layer is called a slime layer
– Firm layer is a capsule
• locomotion by flagella that rotate (not made of
microtubules)
– Movement based on taxis, response to stimuli
Cell Wall Characteristics
• cell wall to provide protection (two
types are identified by gram staining)
Gram Positive - stain purple (thick)
Gram Negative - stain pink (thin)
staining colors differ because of the
thickness of the peptidoglycan layer
Cell Wall Characteristics
Eubacteria Classification • 6 Phylums:
1. Cyanobacteria- abundant
2. Spirochaeles- (spirochetes), corkscrew shape
3. Firmicutes- low GC gram positives
4. Actinobacteria- high GC gram positives
5. Chalmydiales- intracellular parasites
6. Proteobacteria- diverse, 5 groups (α,β,γ,δ,ε)
2
3
6 2
5
4
Firmicutes
Chalmydiales
Eubacteria Classification
• 3 shapes
– bacilli (rod)
• vibrios (bent rods)
– cocci (sphere)
– spirila (spiral)
Eubacteria Classification Growth Patterns
• grow in characteristic patterns
– strepto- chains of cells
– staphylo- resembles grapes
– diplo- paired arrangement of cells
Eubacteria Naming • The two names are put together
to name bacteria
– Growth Pattern + Shape = NAME
• Rod & Pairs
• Round & Clusters
• Spiral & Chains
Eubacteria Classification
Energy Acquisition
• Photoautotrophic
– Perform photosynthesis
– Often called cyanobacteria
• Made aerobic respiration possible
• Chemoautotrophic
– Derive energy from chemical reactions that
break down inorganic molecules
– Chemolithotrophs vs chemoorganotrophs
• Heterotrophic
– Feed on organic substances
– Can create symbiotic relationships
Bacterial Reproduction
Asexual
Reproduction
BINARY FISSION
Vertical Gene Transfer
Bacterial Reproduction Asexual Reproduction
BINARY FISSION-
1. the bacteria copies its chromosome
2. the 2 copies of the chromosome
attach to the plasma membrane
3. cell grows and separates
Bacteria Reproduction
Sexual
Reproduction
Horizontal Gene Transfer
1. Conjugation
One bacteria transfers all
or part of its chromosome
to another cell through a
bridge-like structure called
a pilus/conjugation tube.
Bacteria Reproduction Sexual
Reproduction
Horizontal Gene Transfer
2. Transduction – genetic exchange occurs via a viral vector
Bacteria Reproduction Sexual
Reproduction
Horizontal Gene Transfer
3. Transformation –
bacteria take up
naked DNA without
cell to cell contact
Ways to Gain Resistance
Transformation-
bacterial cells take
in DNA from the
environment
Transduction- a virus
carries a bacterial
gene to another
bacteria
Bacteria Vocabulary • Obligate aerobes- need O
2 to survive
Ex: Mycobacterium tuberculosis
• Obligate anaerobes- killed by O2, require anoxic
environments Ex: Clostridium tetani
• Facultative anaerobes- can live with or without
oxygen Ex: E.coli & Salmonella
• Saprophytes- heterotrophic bacteria that feed
on dead and decaying material
Bacteria Survival
• Bacteria produce endospores during
rough times
– An endospore is a tiny structure that
contains the bacteria’s DNA and a small
amount of cytoplasm and enzymes which is
encased by a tough outer covering.
• During this period of rest, the bacteria
is protected from drying out and harsh
chemicals
• When conditions are favorable again,
the bacteria will reproduce
• Bacteria can remain viable for
thousands of years
Root Nodules