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earliest prokaryote fossils date back at least ______ years
3.5 billion
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Prokaryotes play key roles in:
- 1. Organic breakdown
- 2. Nutrient cycling
- 3. Diseases of humans and otherorganisms
- 4. Bioremediation
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In 1977, ______ (at Univ of Illinois) revised tree of life into three domains- _________- using differences in the ____ to determine relationships between the organisms.
Carl Woese/ eukaryotes, bacteria and archaea/rRNA
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eukaryotes and______ are more closely related than
______and______
archaea/ bacteria&archaea
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•Among the Bacteria, three shapes are common:
-Sphere or coccus (plural cocci), occur singly or in plates, blocks, or clusters.-Rod—bacillus (plural bacilli)-Helical-Rods and helical shapes may form chains.
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•Morphology of known species of Archaea includes _____, _____, _________, and _______
cocci, bacilli, triangular, and square-shaped; the latter grow on surfaces, arranged like sheets of postage stamps.
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Biofilms
Communities of different species of prokaryotes, including microscopic eukaryotes, excrete a gel-like polysaccharide matrix.
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______ may be impenetrable to antibiotics.
Biofilms
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Bacterial cell walls have_________, a polymer of amino sugars.
Archaea do not have__________, although some have a similar molecule called________________.
- peptidoglycan, peptidoglycan
- pseudopeptidoglycan
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Gram-positive bacteria retain the violet dye; they have a _____ layer of peptidoglycan outside the plasma membrane
Gram-negative bacteria retain the red dye; they have a____ layer of peptidoglycan between the plasma membrane and another distinct outer membrane, in the periplasmic space
thick
thin
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____________interfere with the synthesis of the cell walls, but don’t affect eukaryote cells.
Antibiotics such as penicillin
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Quorum sensing
- •Bacteria can monitor the size of the population by sensing the amount
- of chemical signal present.
When numbers are large enough, activities such as biofilm formation can begin.
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bioluminescence
Often the bacteria only emit light when a quorum has been sensed.
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Anaerobes
do not use oxygen as an electron acceptor in respiration.
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obligate anaerobes
molecular oxygen will kill these oxygen-sensitive prokaryotes
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Facultative anaerobes
can shift their metabolism between aerobic and anaerobic modes, such as fermentation
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Photoautotrophs
perform photosynthesis using light as the energy source, and CO2 as their carbon source.
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Photoheterotrophs
are bacteria that also use light as an energy source, but get carbon from organic compounds made by other organisms
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Chemolithotrophs
get their energy by oxidizing inorganic compounds, and use the energy to fix CO2 as their carbon source.
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Chemoheterotrophs
obtain both energy and carbon from complex organic compounds
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Flowchart of nutritional mode of organisms
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3 reasons why nucleotide sequencing of ribosomal RNA is useful in evolutionary studies:
-rRNA is evolutionarily ancient and all free-living organisms have rRNA
-rRNA has the same role in translation in all organisms, lateral transfer is unlikely
-rRNA has evolved slowly; sequence similarities are easily found
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Lateral gene transfer
occurs when genes from one species become incorporated into the genome of another species (moving “sideways” in the tree).
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Mechanisms
transfer by plasmids or virus, and uptake of DNA via transformation
•Transfer can occur between the domains.
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hardy weinburg/isotopic decay
LOOK THIS SHIT UP
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•Over __ clades of bacteria have been proposed under the currently accepted classification scheme.
We will focus on examples from __ clades
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