prokaryotic life characteristics, classification, evolution
TRANSCRIPT
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Prokaryotic life
Characteristics, Classification, Evolution
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• E. coli, a Typical Eubacterium
Peptidoglycan
Cell Membrane
Ribosomes
PiliDNAFlagellum
Cell Wall
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Characteristics• Small
– few micrometers in length• Unicellular• No nucleus• May have flagella for
movement
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Characteristics
• Have a cell wall– May contain peptidoglycan
(a sugar & protein polymer)• Found Everywhere• Many Cause Disease• Many are Useful• Very diverse
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•Prokayotes can be autotrophs or heterotrophs
-Autotrophs: -Self producers, by sunlight or organic chemicals
-Heterotrophs:
- Consumes energy from other organisms
•Energy can be released by:•cellular respiration if there is oxygen available •fermentation if there is no oxygen.
Characteristics
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Classification
• Divided into 2 Domains: – Archaea– Bacteria
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Hot Spring Pool @ Yellowstone
Deep Ocean Vent
Compost
Food
Cavities
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Archaebacteria vs. EubacteriaArchaebacteria • Are ancient. • Lack peptidoglycan.• Live mostly in harsh
environments – Salty lakes– Thick mud– Deep ocean vents– Guts of animals
Eubacteria• Considered “true bacteria”• Have peptidoglycan.• Live almost everywhere.
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Classification
• Can be classified by shape:– Cocci- round– Bacilli- rod shaped– Spirilla- spiral
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3 Possible Shapes of Bacteria
Bacilli
Cocci
Spirilla
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Prefixes Used to Describe & Identify Bacteria:
•Diplo = 2– Neisseria meningitidis (aka diplococcus meningitidis)
•Strepto =chain– Streptococcus pneumonia
•Staphylo =clumps –Ex: Staphylococcus aureus
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• Gram Staining - used to identify bacteria with extra membranes– Extra membrane helps them to better resist damage and
means they are usually more pathogenic (disease causing).
– Gram + stain purple (have peptidoglycan)– Gram – (extra membrane) stain red
Classification
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• Their success depends on the selective pressures that are applied.
• If they can survive their environment they will survive to reproduce and spread.
• Obstacles that bacteria have to overcome:
– Temperature
– Food
– Chemical balance
– Antibiotics
– Antimicrobials
Evolution
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Why so successful in evolving?
• Recall: All living organisms have evolved from a common ancestor.
• Short, rapid reproduction time
• Diversity of bacteria: Bacteria can be found virtually everywhere. They are in the air, soil, water, and in and on plants and animals, including us.
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Examples of bacterial evolution:
• Bacterial resistance to anti-biotics
• Bacterial resistance to anti-microbials (hand sanitizer/soap)
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Bacteria can share genetic content. This is why bacteria are so successful: the sharing of advantageous traits may enable evolving species to become even more successful.
Evolution of antibiotic resistant bacteria
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Prokaryotic Reproduction
Binary fission and Conjugation
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Bacterial Reproduction
• They can reproduce in 2 main ways:– Binary Fission (asexual): splitting in half– Conjugation (sexual): sharing genetic info
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Binary Fission Video
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-Conjugation (sexual) : swapping genes over a bridge between two bacteria
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Successful Evolution
• Bacteria can reproduce very rapidly! – E.coli can reproduce in just 20 minutes!
• Environments exert natural selection on populations causing them to change.