prokaryotic profiles
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Prokaryotic profiles. When did prokaryotes first appear?. What are the basic differences?. How do prokaryotes compare in size with other microorganisms?. How do I describe their shapes? . Is a species always the same shape?. Generally, yes Monomorphic however, environment can alter - PowerPoint PPT PresentationTRANSCRIPT
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Prokaryotic profiles
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When did prokaryotes first appear?
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What are the basic differences?
Characteristic Prokaryotes Eukaryotes
# of cells Unicellular Uni or multi
DNA shape DNA is circular, no histones
DNA in chromosomes w/histones
DNA location Free in cell In PM-bound nucleus
True organelles? No Yes
Ribosomes 70S 80S
First amino acid in protein
Formylmethionine Methionine
Cell wall? Yes-peptidoglycan No (animalia); Yes (plantae—cellulose); Fungi (chitin)
Reproduction Binary fission three ways to reproduce
Mitosis
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How do prokaryotes compare in size with other microorganisms?
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How do I describe their shapes?
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Is a species always the same shape?
• Generally, yes– Monomorphic– however,
environment can alter
• Some are pleiomorphic
Photo from: uhavax.hartford.edu/bugl/Yersinia-pestis.jpg
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The partsStarting from the outside and working
inward
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What’s outside the cell wall?• Glycocalyx
– Carbohydrates and/or peptides
– Viscous– Can protect bacterium– Some help cells attach
• Teeth: Streptococcus mutans
• Capsule– Organized– Firmly attached to cell
wall• Slime layer
– Unorganized– Loosely attached
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What are flagella?• Singular = __________• Monotrichous• Amphitrichous• Lophotrichous• Peritrichous
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What do flagella do?
• Run and tumble
• Swarming• Allow for
taxis– Chemotaxis– Phototaxis
• dancing bacteria!
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What are axial filaments?
• AKA periplasmic flagella
– Fibril bundles that spiral around cell
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What’s the difference between fimbriae and pili?
• Found primarily on gram-negative bacteria
• For attachment, not movement
• Pilin protein • Fimbriae
(fimbria, singular)– Attachment
• E.g. to mucosal membranes
• Pili (pilus, singular)– For DNA
exchange only
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What’s in the cell wall?
• Peptidoglycan (PPG)– AKA murein– NAG-NAM
disaccharide• NAG = N-
acetyleglucosamine• NAM = N-
acetylemuramic acid
– Lysozyme disrupts NAG-NAM bond
• If lysis doesn’t occur, cell is called a protoplast
– Linked with tetrapeptide
• Penicillin disrupts lysis
• penicillin killing cells
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What’s in the cell wall?
• Gram positive bacteria– Many PPG layers– Teichoic acids
• Different types• Used for antigenic specificity
tests
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What’s in the cell wall?
• Gram negative bacteria– One or few PPG layer(s)– Outer membrane: lipopolysaccharides (LPS), lipoproteins,
phospholipids• Periplasm separates LPS from the PM (PPG is in periplasm)• Provides barrier to some antibiotics, digestive enzymes• Porins allow for access into cell
– LPS used for specific antigen tests to I.D. species
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What does a side-by-side comparison look like?
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More comparison
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How does this relate to gram staining?
• Hint: What does the LPS layer covering the gram negative cell do to it?
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What are atypical cell walls?
• Mycoplasma– Smallest known
independent bacteria– No cell walls– Often mistaken for
viruses– PM has sterols to
prevent lysis• Mycobacteria
– Mycolic acid in cell wall
• Hydrophobic• Acid-fast stain
identifies• Tuberculosis,
leprosy• Archaea
– Some have cell walls but not with PPG
– Pseudo-murein
Mycoplasm pneumoniae
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What happens if the cell wall is damaged?
• Lysozyme lyses gram positive, but usually does not harm gram negative to the same extent– Why?
• Protoplast: gram positive• Spheroplast: gram negative• Osmostic lysis
– If placed in a hypotonic environment
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What’s inside the cell wall?• Plasma membrane
– Phospholipid bilayer– Fluid mosaic theory
• Segregates DNA during binary fission• Secretes enzymes to make PPG, teichoic acid• ATP production• Selective permeable membrane…
– Active vs. passive transport
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What kinds of passive transport exist?
• Simple diffusion– For small, lipid-
soluble substances• Osmosis
– Water movement via diffusion
– Happens whenever difference in concentration across PM
– Note: water often moves because solutes can’t• Because PM is only
semi-permeable
Simple diffusion
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What do you think will happen?
A. Left side increases with waterB. Right side increases with waterC. No net movement of water
Click here to show what actually happens: answer animation
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What is osmosis?• Water concentration depends on number of solutes
in it– Hypertonic– Isotonic– Hypotonic
• Water moves down its concentration gradient until osmolarity is equal
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What do you think will happen?
10% glucose
20% glucose Distilled water 10% glucose
For each, choose from
A. No net change B. cell swells C. cell shrinks
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What is facilitated passive diffusion?
• Protein-assisted diffusion– Transporte
rs or carriers• Amino
acids, glucose
– Channels (AKA “pores”)• Most are
gated (usually closed)
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What is active transport?• Movement of solute against gradient
– Can you think of examples of where this might happen in your body?
• Requires energy b/c moving against gradient– From ATP
• Proteins sometimes called “pumps”
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What is group translocation?• Type of active transport
– Only in prokaryotes– Chemically altered as it is pulled across PM into cell
• Once inside, cannot exit• E.g. glucose phosphorylation
• Animation
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What is the cytoplasm?
• Eukaryotes– Cytosol +
organelles• Prokaryotes:
all stuff inside cell– 80% water +
nuclear area, ribosomes, inclusions (storage areas)
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What is the nuclear area?
• AKA nucleoid• Circular, double-
stranded DNA– Called bacterial
chromosome• Plasmid
– Also double-stranded DNA
– Independent replication
– Associated with PM proteins
– Can gain or lose without killing cell
– Can provide resistance to antibiotics, etc.
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What are ribosomes?• Manufacture proteins• Two subunits
– Each with proteins and rRNA– 70S ribosomes (smaller than eukaryotes)
• 50S and 30S subunits• Eukaryotes = 80S ribosomes (60S + 40S)
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What are inclusions?• Storage areas• Metachromatic
granules– Collectively
called volutin• Phosphate
reserve for making ATP
• Polysaccharide granules– Iodine stain
shows these• Others with
– Lipids, sulfur granules, etc.
– Magnetosomes: iron oxide
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What are endospores?
• Usually gram-positive bacteria– Not a reproductive
structure– Survival structure for bad
times• Inside PM
– Form thick walls– Tolerate high heat,
dehydration, poisons, radiation
– Can survive up to 25 to 40 M years!!!!!!!!
– Problem for food industry!
• Botulism
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How are spores formed?
• Sporogenesis– Usually resource
scarcity triggers• Carbon, nitrogen,
etc.– Spore is highly
dehydrated • Vegetative state
• Favorable conditions– Germination
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Prokaryotic domain
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What are taxonomic groups of bacteria?
• Gracilicutes– Gram -
• Firmicutes– Gram +
• Tenricutes– (no cell cell—e.g. mycoplasmas)
• Mendosicutes– (Archaebacteria)
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What’s the difference between a species and a strain?
• Species: share similar pattern of traits
• Subspecies/strain/type: same species with differing characteristics
• Serotypes: unique antibody response in host
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What about unusual bacteria?
• Rickettsias– Parasitic,
gram negative
– Arthropod vector
– RMSF– Q Fever
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• Chlamydias– Parasitic– No vector
What about unusual bacteria?
Photo from: http://www.sexually-transmitted-diseases.info/images/std_chlamydia.jpg
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What about Mendosicutes?
• No PPG• 70S• Extremophiles
– Halophiles– Thermophiles– Methanophile
s
Photo from: http://people.westminstercollege.edu/faculty/tharrison/gslfood/studentpages/pinkwater2.JPG