Chapter 27~Prokaryotes and the Origins of Metabolic Diversity.
Ch. 27 Prokaryotes
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Transcript of Ch. 27 Prokaryotes
Ch. 27 ProkaryotesDomain Bacteria
Domain Archaebacteria
2007-2008
DomainBacteria
DomainArchaea
DomainEukarya
Common ancestor
Bacteria live EVERYWHERE!• Bacteria live in all ecosystems– on plants & animals– in plants & animals– in the soil– in depths of the oceans– in extreme cold– in extreme hot– in extreme salt– on the living– on the dead
Microbes alwaysfind a way tomake a living!
Bacterial diversityRods(bacilli) and spheres(cocci) and spirals(helical)…Oh My!
Prokaryote Structure• Unicellular– bacilli, cocci, spirilli
• Size– 1/10 size of eukaryote cell• 1 micron (1um)
• Internal structure– no internal compartments• no membrane-bound organelles• only ribosomes
– circular chromosome, naked DNA• not wrapped around proteins
prokaryotecell
eukaryote cell
Variations in Cell Interior
internal membranesfor photosynthesis
like a chloroplast(thylakoids)
internal membranes
for respiration
like a mitochondrion
(cristae)
aerobic bacterium
mitochondria
cyanobacterium(photosythetic) bacterium
chloroplast
Prokaryote Cell Wall Structurepeptide side
chains
cell wallpeptidoglycan
plasma membrane
protein
Gram-positive bacteria
Gram-negative bacteria
peptidoglycan
plasmamembrane
outermembrane
outer membrane of lipopolysaccharides
cell wall
peptidoglycan = polysaccharides + amino acid chainslipopolysaccharides = lipids + polysaccharides
That’simportant foryour doctorto know!
Motility• 1- Flagella• 2- Helical shape
(spirochetes)• 3- Slime• 4-Taxis
(movement away or toward a stimulus)
Form & Function• Nucleoid region (genophore: non-
eukaryotic chromosome)• Plasmids• Asexual reproduction: binary fission
(not mitosis)• “Sexual” reproduction (not meiosis):
• transformation~ uptake of genes from surrounding environment
• conjugation~ direct gene transfer from 1 prokaryote to another transduction~ gene transfer by viruses
• Endospore: resistant cells for harsh conditions (250 million years!)
Genetic variation in bacteria• Mutations– bacteria can reproduce every 20 minutes
• binary fission
– error rate in copying DNA• 1 in every 200 bacteria has a mutation• you have billions of E. coli in your gut!– lots of mutation potential!
• Genetic recombination– bacteria swap genes
• plasmids– small supplemental
circles of DNA
• conjugation– direct transfer of DNA
conjugation
Nutrition & Metabolism• Photoautotrophs: photosynthetic; harness
light to drive the synthesis of organics (cyanobacteria)
• Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO2
• Photoheterotrophs: use light to generate ATP but get carbon in an organic form
• Chemoheterotrophs: consume organic molecules for both energy and carbon– saprobes- dead organic matter
decomposer– parasites- absorb nutrients from living
hosts• Oxygen relationships: obligate aerobes;
facultative anaerobes; obligate anaerobes
Bacteria as pathogens– animal diseases• tooth decay, ulcers• anthrax, botulism• plague, leprosy, “flesh-
eating” disease• STDs: gonorrhea,
chlamydia • typhoid, cholera • TB, pneumonia• lyme diseaseplant diseases• wilts, fruit rot, blights
opportunistic: normal residents of host; cause illness when defenses are weakened •Koch’s postulates: criteria for bacterial disease confirmation•exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) •endotoxins: components of gram - membranes (Salmonella)
Bacteria as beneficial (& necessary)• Life on Earth is dependent on bacteria– decomposers
• recycling of nutrients from dead to living
– nitrogen fixation• only organisms that can fix N from atmosphere
– needed for synthesis of proteins & nucleic acids– plant root nodules
– help in digestion (E. coli)• digest cellulose for herbivores
– cellulase enzyme
• produce vitamins K & B12 for humans
– produce foods & medicines• from yogurt to insulin