chapter 23: bacteria. overview on bacteria -microscopic -unicellular organism -prokaryote: –lack...
TRANSCRIPT
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Chapter 23: Bacteria
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Overview on Bacteria
-Microscopic-Unicellular
organism-Prokaryote:
– lack of membrane bound nucleus and organelles
– found everywhere– harmful and beneficial
types of bacteria– believed to have
existed 3.5 billion years ago
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ClassificationBacteria are classified based upon the
following characteristics: structure, physiology, molecular composition and reaction to staining.
Two kingdoms…new version = Domains!
1. Archae
-ancient, living in extreme environments
-not commonly exposed to humans
2. Eubacteria
- “bacteria” and germs
-commonly exposed to humans
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Domain: ArchaeCharacteristics:
Unusual lipid cell membraneIntrons in their DNANo Peptidoglycan *Lives in extreme environmentsrRNA is similar to rRNA in eukaryotesgenes are similar to eukaryotes
Peptidoglycan: protein carbohydrate found in cell walls
Archaeal Groups:1) Methanogens2) Halophiles3) Thermoacidophiles
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Methanogens
• Harvest energy by converting H2 and CO2 into methane gas.
• Anaerobic environments• Facilitate fermentation• Location:
– Intestinal tracks, MARSH GAS, swamps and sewage
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Extreme Halophiles• Found in salty
environments
• Use salt to generate ATP
Thermoacidophiles• Found in acidic and high
temperature environments• pH less than 2• Temp: up to 230oF
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Domain: Bacteria
Characteristics:normal lipids in cell membrane
no introns
have peptidoglycan
live in a variety of environments
rRNA is different than rRNA of eukaryotes
genes are not like genes of eukaryotes
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Eubacteria
Streptococci = chain of cocciStaphylococci = cluster of cocci
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Gram StainingGram Positive
• Thick layer of peptidoglycan in cell wall.
• Cause: retains purple stain.
Gram Negative• Thin cell wall (very small
layer of peptidoglycan).• Cause: unable to retain
stain and appears pink.
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Cell Membrane
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Phylum• Cyanobacteria:
– Blue- green algae– gram –– Photosynthetic: capture sunlight to harvest energy
• Spirochetes:– Syphilis (STD and parasite)– Gram -
• Gram positive Bacteria:– Found in soil and used to produce antibiotics
• Proteobacteria:– Largest, most diverse– gram –– Heterotrophic, chemoautotrophic, nitrogen fixing
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Structure
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Structures• Cell wall
-Peptidoglycan
- Antibiotics (resistance)
• Cytoplasm-DNA, ribosomes, membrane for cell respiration
• Capsule and Pili-protective outer covering
-Glycocalyx: sticky covering used for attachment
- Pili: hair-like protein structures used for attachment.
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Structures
•Endospore - Dormant - Protects DNA during harsh conditions (chemicals, radiations, temperature changes) - Bacillus and Clostridium
•Movement -Flagellum - Rotating (spiral-shaped bacteria) - Slime (myxobacteria)
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Nutrition and GrowthAutotrophs
• Photoautotrophs: use sunlight as an energy source
• Chemoautrophs
Heterotrophs
• Saprophytes : feed on dead organic matter
• ANAEROBE = NO O2 AEROBES = YES O2
• Obligate Anaerobe (C. tetani)• Facultative Anaerobe (E. coli)• Obligate Aerobe (M. tuberculosis)
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Reproduction and Recombination
•Transformation- Bacterial cells take DNA from an outside source and substitute for a similar DNA fragment in the chromosome of the cell.
•Conjugation- Two bacteria bind together and transfer genetic material to one another.- Conjugation Bridge: passageway used to transfer genetic material-Plasmids
•Transduction- a virus obtains a fragment of DNA from a bacterium.
Replication of the virus results in new bacterium.
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PathologyThe study of disease
• Exotoxins : protein toxins – Gram positive bacteria
• ex: Tetanus
• Endotoxins: lipid and carbohydrate toxins– Gram negative bacteria– Released when bacteria die– Symptoms: fever, body aches and weakness
• ex: E. coli
What can we do to avoid diseases
caused by bacteria?
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Name that pathogen!
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Streptococcus mutans
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Borrelia burgdorferi
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Streptococcus pyogenes
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Heliobacter pylori
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Neisseria meningitidis
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Antibiotics
Gram Positive Antibiotics
• Penicillin: inhibits cell wall synthesis
• Cephalosporin• Sulfa-drugs (synthetic):
inhibits cell metabolism Ex: bacterial meningitis
Broad Spectrum/ Gram Negative Antibiotics
• Tetracycline: Inhibits protein synthesis. Ex: skin infections (acne) and Lyme disease
• Ampicilin: Inhibits cell-wall synthesis
• Zithromax (Z Pack): inhibits protein synthesis
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Benefits of Bacteria
Healthy flora (E. coli) in the intestinal trackEx: Enteric Bacteria
Lactobacillus found in sour dough bread.(Fermentation)
AcidophilusProbiotics
A mouse?