Chapter 27 p. 534-540. MMost abundant organisms on Earth AAble to grow in hot, cold, salty, acidic,...
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Transcript of Chapter 27 p. 534-540. MMost abundant organisms on Earth AAble to grow in hot, cold, salty, acidic,...
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PROKARYOTES AND THE ORIGIN
OF METABOLIC DIVERSITY
Chapter 27p. 534-540
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PROKARYOTIC LIFE: AN OVERVIEW Most abundant organisms on Earth
Able to grow in hot, cold, salty, acidic, or basic (alkaline) conditions
2 Types:Archaea: “ancient” live in extreme
environments similar to early EarthBacteria: modern bacteria
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PROKARYOTIC LIFE: AN OVERVIEW Most are beneficial or non-harmful
Provide vitamins to humansCycle elements through biosphere (C)Are decomposers (digest dead/decaying
organisms)Form symbiotic relationships w/ other prokaryotes
& eukaryotes
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STRUCTURE
Mostly unicellularMay aggregate into
groups called colonies
Shapes:Cocci: sphereBacilli: rodHelices: spiral or
corkscrew Diameter = 1-5
μm
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CELL WALLS Maintains shape, protects, prevents
burstingSusceptible to plasmolysis (shrinkage)
Bacteria (not archaea) contain peptidoglycanGram Stain: tests for peptido.
Gram + = ↑ peptido.; stains purpleAntibiotics will inhibit peptido. formation
Gram - = ↓ peptido.; stains pinkCells have outer membrane of
lipopolysaccharidesGenerally more toxic (outer membrane protects)
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CELL WALLS (CON’T) Capsule: sticky
substance outside cell wallAids in cell adhesion
(colonies) & protectsPolysaccharide or protein
Fimbriae: numerous hair-like appendages used to attach to host cell
Pili: hold cells together Sex Pilus: used on
conjugation
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MOTILITY Flagella: long cellular appendage Composed of:
Basal Apparatus (motor): uses chemiosmosis (H+ diffusion INTO cell) to turn the hook
Hook: anchors filament to basal apparatus & turns Filament: composed of long chain of flagellin protein Under outer layer of cell wall
Taxis: movement toward/away from stimulusi.e.: chemical, light, magnetic field, each other (colonies)
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CELLULAR & GENOMIC ORGANIZATION Instead of organelles,
have infolds of plasma membrane for metabolism
Nucleoid Region: where DNA located1 ring of ss DNA
(“genophore”) Plasmids: smaller separate
rings of DNA Have smaller
ribosomes; susceptible to antibiotics
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GROWTH & ADAPTATION Binary Fission: asexual
reproduction; can exchange DNA by:1) Transformation: intake
from environment2) Conjugation: exchange
between 2 cells3) Transduction: w/ help of
viruses Mutations are main
source of genetic variationVery fast reproduction →
spread rapidlyAccelerated natural
selection
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GROWTH & ADAPTATION (CON’T)
Prokaryotic “growth” = multiplication1-3 hours Inhibited by medium
or accumulation of waste
Endospores: thick-coated resistant cells formed within bacterial cellRequires ↑↑ temps
to kill (120°C min.)May remain dormant
& re-emerge
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NUTRITIONAL & METABOLIC DIVERSITY All species require energy & C source 1) Photoautotrophs: light + CO2
i.e.: cyanobacteria (also plants & algae) 2) Chemoautotrophs: chemical (H2S,
NH3, Fe2-) + CO2
i.e.: Sulfolobus 3) Photoheterotrophs: light + organic
nutrientsrare
4) Chemoheterotrophs: chemical + organic nutrients i.e.: saprobes & parasites