prokaryotic profiles. when did prokaryotes first appear?
TRANSCRIPT
Prokaryotic profiles
When did prokaryotes first appear?
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
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
• Some are pleiomorphic
Photo from: uhavax.hartford.edu/bugl/Yersinia-pestis.jpg
The partsStarting from the outside and working
inward
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
What are flagella?• Singular = __________• Monotrichous• Amphitrichous• Lophotrichous• Peritrichous
What do flagella do?
• Run and tumble
• Swarming• Allow for
taxis– Chemotaxis– Phototaxis
• dancing bacteria!
What are axial filaments?
• AKA periplasmic flagella
– Fibril bundles that spiral around cell
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
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
What’s in the cell wall?
• Gram positive bacteria– Many PPG layers– Teichoic acids
• Different types• Used for antigenic specificity
tests
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
What does a side-by-side comparison look like?
More comparison
How does this relate to gram staining?
• Hint: What does the LPS layer covering the gram negative cell do to it?
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
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
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
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
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
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
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
What is facilitated passive diffusion?
• Protein-assisted diffusion– Transporte
rs or carriers• Amino
acids, glucose
– Channels (AKA “pores”)• Most are
gated (usually closed)
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”
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
What is the cytoplasm?
• Eukaryotes– Cytosol +
organelles• Prokaryotes:
all stuff inside cell– 80% water +
nuclear area, ribosomes, inclusions (storage areas)
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.
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)
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
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
How are spores formed?
• Sporogenesis– Usually resource
scarcity triggers• Carbon, nitrogen,
etc.– Spore is highly
dehydrated • Vegetative state
• Favorable conditions– Germination
Prokaryotic domain
What are taxonomic groups of bacteria?
• Gracilicutes– Gram -
• Firmicutes– Gram +
• Tenricutes– (no cell cell—e.g. mycoplasmas)
• Mendosicutes– (Archaebacteria)
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
What about unusual bacteria?
• Rickettsias– Parasitic,
gram negative
– Arthropod vector
– RMSF– Q Fever
• Chlamydias– Parasitic– No vector
What about unusual bacteria?
Photo from: http://www.sexually-transmitted-diseases.info/images/std_chlamydia.jpg
What about Mendosicutes?
• No PPG• 70S• Extremophiles
– Halophiles– Thermophiles– Methanophile
s
Photo from: http://people.westminstercollege.edu/faculty/tharrison/gslfood/studentpages/pinkwater2.JPG