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