3/17/13 - Gram +/-

Question 1

What are Koch’s Postulates?

Answer 1

1) Find the bacteria in disease.
2) Grow the bacteria in pure culture.
3) Reproduce the disease in animals using the pure culture.
4) Reisolate the bacteria from the experimental infection

Question 2

Koch’s molecular postulates

Answer 2

1) Phenotype under investigation should be associated with a pathogenic organism
2) speific inactivation of a gene should lead to decrease in virulence
Restoration of pathogenicity should result by replacing the mutated virulent gene with the WT

Question 3

Classes of Microorganisms

Answer 3

1) Algae - no pathogen, all photosynthetic
2) fungi - some pathogen, non photo, rigid cell wall (chitin)
3) Protosoa - some pathogens, no rigid cell wall, unicellular, nonphoto ( some cysts have rigid walls)
4) Bacteria - many pathogens, many need organic compounds as energy source. Some non-pathogens are photo. All, but one, have rigid cell wall

Question 4

Chromosomes - Euk vs Prok

Answer 4

Eucaryotic - nuclear membrane. Linear chromosomes, mitosis

Procaryotic - one circular chromosome not bound by nuclear membrane. Chromosome segregation, no mitosis.

Question 5

MT and other membrane structures - Euk vs Prok

Answer 5

Eucaryotic - MT has oxidative enzymes for oxidative phosphorylation. Vacuoles, perioxisomes

Procaryotes - No MT. Oxidative phosphorylation associated with cytoplasmic membrane

Question 6

Cellular movements - Euk vs Prok

Answer 6

Eucaryotic - cytoplasmic steaming (amoeboid) or contraction of flagella (cilia). Cilia is a 9+2

Procaryotic - No cytoplasmic streaming. Some have flagella known as H-antigen. No microtubules. Instead, it is a long helical rod made of flagellin. No membrane coat.

Question 7

Cell wall - Euk vs Prok

Answer 7

Not found in animal cells

Eucaryotic - higher plants and algae made of polysaccharide cellulose. In fungi is made of chitin and beta 1,3 glucan.

Prokaryotic - made of a peptidoglycan polymer, containing MURAMIC acid (made of acetyl glucosamine) and D-AA. Penicillin interferes with formation of peptidoglycan.

Question 8

RNA - Euk vs Prok

Answer 8

Eucaryotic - RNA transcribed in nucleous, spliced and transported to ER for protein making.

Procaryotic - no nucleous, RNA translated as made. No splicing.

Question 9

Size of Bacteria

Light microscope resolving power

Answer 9

~1 um (0.001 mm, 1000 nm)

Light - 0.2um

Question 10

Morphology of Bacteria

Answer 10

1) Coccus
(Pneumococcus and Gonococcus are elongated cocci. Staph is perfect circle)

2) Rod / Bacillus
(some gram - rods look a lot like cocci)

3) Curved Rod or spiral
(spirochetes, such as Treponema pallidum that causes syphillis - dont have a very rigid cell wall.

Question 11

Arrangements

Answer 11

1) chain of cocci - Steptococci)
2) irregular cocci - Staphylococci
3) rod division at right angles - common among aerobic Bacilli
4) stacks of rods - corynebacterium

Question 12

Binary fission

Answer 12

Bacteria multiplication using a central transverse wall.

Question 13

Contents of a typical bacterial cell

Answer 13

1) Cytoplasmic membrane
2) Nuclear equivalents (nucleoid)
3) Cell wall
4) Capsule (optional)
5) Flagella (optional)

Question 14

Cytoplasmic membrane

Answer 14

Semipermeable phospholipid bilayer. Rarely contains sterols.

Function:

1) contains oxidative enzymes and resembles inner membrane of MT
2) contains enzymes that make cell wall
3) Transport - active, selective, diffusion
4) excrete toxins

Question 15

Nucleoid

Answer 15

Bacteria nuclear equivalent. No chromosome or membrane

Question 16

Periplasmic space

Answer 16

Between cytoplasmic membrane and outer membrane. Find enzyme degrading extracellular substances

Question 17

Ribosomes

Answer 17

Bacterial is 70S (human 80S) and is smaller

Question 18

Cytoplasmic Granules

Answer 18

Storage bodies in cytoplasms when excess food is available. Ex - high molecular weight lipid or glycogen.

Metachromatic granules - polymerized phosphate. Stains dark, dound in Diptheria (Corynebacterium diphtheriae)

Question 19

Cell wall

Answer 19

20-30% weight. All except MYCOPLASMA have cell wall. The structure is a polymer of N-acetyl glucosamine (NAG) linked to muramic acid by glycosidic bond. Also linked to 4 AA in a D-conformation

Peptidogycan

CROSS-Linking gives rigidity - Binding through AA side chains of COOH of tetrapeptide to another neighbor

Question 20

Muramic acid

Answer 20

N-acetyl glucosamine linked to lactic acid.

Question 21

Penicillin

Answer 21

Blocks cross-linking of peptidoglycan

Question 22

Lysozyme

Answer 22

splits glycosidic bond between N-acetyl glucosamine and muramic acid.(NAG)

Question 23

Gram positive characteristics

Answer 23

Contain thick peptidoglycan as well as different carbohydrate polymers. No phospholipid outer membrane.

Examples - staphylococcus, streptococcus

Ribitol phosphate (sugar alcohol) in staph or teichoic acid linked to peptidoglycans act as antigens. in outside later of peptidoglycan.

Order:
Polymer
Peptidoglycan
cytoplasmic membrane

Question 24

Gram negative characteristics

Answer 24

Peptidoglycan later (mucopeptide) is thinner. They have an outer membrane OM whcih contains lipoposaccharides on the outer surface (LPS).

Order:
OM
Peptidoglycan
Cytoplamic membrane

Periplasmic space found ONLY in gram - bacteria. Contains binding proteins and hydrolytic enzymes. Found between the inner and outer membranes

Porins in outer membrane allow entry of nutrients by diffusion

Question 25

Helical merein lipoproteins

Answer 25

IN g- bacteria, bind peptidoglycan to OM

Question 26

lipid A potion of LPS

Answer 26

Imbedded in base of outer membrane outer leaflet

lipid component of an endotoxin held responsible for toxicity of Gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS, also called endotoxin) molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane

Question 27

teichoic acid

Answer 27

only found in staph. G+

Question 28

OM and Antibiotics

Answer 28

OM servesas barrier to antimicrobial agens and detergens. As well, a lot of antibiotics don’t work bc they can’t reach the cell wall (ex. vancomycin)

Question 29

O specific antigen

Answer 29

Polysaccharides of lipopolsaccharides of LPS on G-. Found on the very surface of the cell

Question 30

Capsule

Answer 30

Found mostly on G- bacteria. acts as protection. Made of polysaccharides

A common mnemonic used to remember some encapsulated pathogens is:

“Even Some Super Killers Have Pretty Nice Capsules”

Escherichia coli, Streptococcus pneumoniae, Salmonella, Klebsiella pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, Neisseria meningitidis, and the yeast Cryptococcus neoformans.

Question 31

Flagella

Answer 31

Made of protein flagellin - long helical rebeat with hollow inside.

Many all over - peritrichous
One end - Polar

Question 32

Pili

Answer 32

Similar to Fimbriae. Filamentous surface appendages. Used for adherance to other cells. F pili used for bacterial conjugation - transfer of DNA

Molecular - Hollow tubes

Gonococcal pilus is an important virulent factor

Question 33

Glycocalyx

Answer 33

On G+ bacteria- slime layer. Adhere to heart valves, teeth.

Question 34

Spores

Answer 34

Foudn in large G+ rods in the genera Bacillus and Clostridia. Sporulation occurs after the rapid phase of growth, as a response to nutrient deprivation.

Made as an endospore - can contain dipicolinic acid.

Keratin Proteinaceous outer coat.

Question 35

Chemotaxis

Answer 35

Attractants - sugars and AA
Repellants - phenols + acids

Chemoreceptors turn on flagellar rotation

Flagella rotation = movement –> counter clock wise = straight
Switch = tumble