Identifying and Classifying Bacteria
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Transcript of Identifying and Classifying Bacteria
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Identifying and Classifying Bacteria
Ch. 23
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What is a prokaryote?Cells that lack a true nucleus.
Cells that lack membrane-bound organelles.
Most surrounded by a cell wall.
Many secrete a protective slime capsule.
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How big is a prokaryotic cell?
1- 5 micrometers (1 millionth of a meter)
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ClassificationArchaebacteria vs Eubacteria
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ArchaebacteriaSurrounded by a cell wall lacking peptidoglycan.
Live in extreme conditions
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Examples of Archae
Methanogens: convert H2 and CO2 into methane gas for energy
Halophiles: love saltThermoacidophiles: love heat and acid
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Eubacteria:
Surrounded by a cell wall made of peptidoglycan.
Example: rhizobium- nitrogen–fixing
bacteria
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Identifying Prokaryotes
1. Shape:• Coccus – spherical• Bacillus – rod-shaped• Spirillum – spiral• Vibrio – comma shape
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Coccus
Spirillum
Vibrio
Bacillus
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Ex. Diplococcus
Cocci and Bacilli may group together
Prefixes for arrangements: Diplo – two
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Strepto – chainStreptococcus
Streptobacillus
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Staphylo - clustered
Staphylococcus
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2. Motility: ability to moveFlagella: whip-like structure used to propel bacteria
Slime: glide along slime secretion
Spiral motion: cork-screw motion (spirillum)
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3. Metabolism: Oxygen or NOT
Obligate Aerobes: Need oxygen
Obligate Anaerobes: cannot live in oxygen
Facultative anaerobes: can live with or without oxygen
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3.Metabolism: Obtaining EnergyAutotroph vs. Heterotroph• Photoautotroph- uses light
energy for photosynthesis• Chemoautotroph- uses
energy from inorganic chemicals for chemosynthesis
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• Photoheterotrophs- uses photosynthesis and eats organic compounds
• Heterotroph – consumes organic compounds
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reviewWhat role do chemosynthetic bacteria have in the ecosystem?
http://www.youtube.com/watch?v=4lmwbBzClAc&NR=1
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Bacterial Reproduction
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Asexual: Binary fission1. Circular DNA replicates2. Cell membrane and cell
wall divide 3. Identical daughter cells
separate
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How fast does this happen?http://www.youtube.com/watch?v=gEwzDydciWc&feature=related
approximately every 20 minutes
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Genetic recombinationSharing or exchanging of genetic material
3 types:1. Conjugation2. Transformation3. Transduction
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1. ConjugationA temporary bridge forms between two cells.
A plasmid, a separate section of DNA, is transferred from one cell to the other.
Often the plasmid contains useful genes, like antibiotic resistance.
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2. TransformationBacteria takes in DNA from the environment.
Dead bacteria may break apart and release DNA.
Other bacteria can pick up this DNA and become genetically different.
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3. TransductionViruses can pick up small amounts of DNA from a host bacteria.
When it infects another bacteria, the new DNA is transferred into that cell.
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DiseasePathology is the study of disease.
Pathogens: organisms that cause disease.
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Gram-staining TestGram-positive: bacteria contain lots of peptidoglycan in cell walls. Stains purple.
Gram- negative: bacteria contain little peptidoglycan in cell walls. Stains red.
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ExotoxinsPoisonous proteins that are released by some gram-positive bacteria.
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For example Clostridium tetani secretes an
exotoxin that causes tetanus.Tetanus causes stiffness in muscles.
Clostridium botulinum produces a very powerful exotoxin that causes the fatal disease, botulism.
1 g of botulism toxin can kill 1 million people.
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EndotoxinsLipids and carbohydrates in the cell membranes of some Gram-negative bacteria, that are poisonous.
They are released when the bacteria die.
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For example:Most species of Salmonella, are endotoxin producing bacteria.
Salmonella typhi, causes typhoid fever.
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AntibioticsAntibiotics interfere with the bacteria’s cellular activities.
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For example:Penicillin: blocks the building of the cell wall.“Accidently” discovered by Alexander Fleming in 1920s
Tetracyline: blocks protein synthesis.
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Where do antibiotics come from?
Antibiotics are naturally made by some fungi and bacteria.
Some are made synthetically in labs.
But most used in treatment still come from bacteria.
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Antibiotic-ResistanceBacteria can quickly adapt to their environment because of their rapid rate of reproduction.
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Antibiotic-Resistance1. If one bacterium mutates
and becomes resistant, 2. then in the presence of
antibiotics, bacteria not resistant die
3. Those with the resistance take over the population.
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Which diseases are preventable by better sanitation practice?
CholeraSalmonellaTetanusStaph
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What are other ways that antibiotic resistance is passed?Genetic recombination