03-18 Bacterial Structure and Function

Question 1

Who discovered bacteria? When?

Answer 1

Antony van Leeuwenhoek in the 1600s

Question 2

cocci

Answer 2

round bacteria

Question 3

bacilli

Answer 3

rod-shaped bacteria

Question 4

What color do Gram(+) bact stain?

Answer 4

violet

Question 5

What color do Gram(-) bact stain?

Answer 5

red

Question 6

What are the original Koch’s Postulates?

Answer 6

1. find bact in all cases of the dz
2. grow pure culture of it
3. reproduce dz by injected subject w/ pure culture
4. re-isolate same bugger

Question 7

What are Koch’s Molecular Postulates?

Answer 7

1. phenotype being investigated is assoc’d significantly more often with a pathogenic organism than w/ non-path strain/member
2. inactivating the gene decreases virulence
3. replacing w/ w.t. gene returns pathogenicity

Question 8

What are the classes of microorganisms? Which are pathogens? Which photosynthesize? Which have cell wall?

Answer 8

algae - not path; all photosynth; have wall
fungi - can be path; no photo; have wall
protozoa - can be path; no photo; no wall
bacteria - can be path; few are photo; all (but one) have wall

Question 9

higher vs. lower microorganisms

Answer 9

higher = euk = algae, fungi and protozoa
lower = prok = bacteria

Question 10

Compare/contrast nucleic acids in proks vs. euks.

Answer 10

BOTH - DNA in chromosomes
Euks - several, linear chromosomes inside a nuclear envelope
Proks - single, circ chromosomes just free-ballin’ it in the cytosol

Question 11

Compare/contrast cell mov’t proks vs. euks.

Answer 11

Euks: cytosolic streaming/amoeboid mov’t; flagella of MTs in 9:2 doublet arrangement
Proks: no cytosolic streaming/amoeboid mov’t b/c there cytosol is so viscous w/ ribosomes; do have flaggela not from MTs but rather of flaggelin and not coated by the membrane

Question 12

Compare/contrast cell wall material in proks vs. euks

Answer 12

Euks - cellulose (plants/algae) or chitin (fungi)

Proks - peptidoglycan w/ muramic acid, D-a.a.’s and other unusual a.a.’s

Question 13

Are archea infectious?

Answer 13

No, not that we know of.

Question 14

Compare and contrast RNA handling proks vs. euks.

Answer 14

euks - pre-mRNA made in nucleus, spliced, exported to cytosol and transcribed
proks - no nucleus, no splicing, new mRNA starts get translate before it is even completely processed

Question 15

What is the size range of most bacteria of medical interest?

Answer 15

most are ~1 micrometer (µm) = 10^-6; smallest (mycoplasma at 0.175µm) overlaps with largest of viruses (pox fam at .250µm)

Question 16

What’s up with spirochetes?

Answer 16

They are in a separate phyla and lack a rigid cell wall

Question 17

What are the medically-relevant patterns of aggregates caused by successive division w/o full separation of cells?

Answer 17

• this occurs most commonly with cocci

- create filaments which can form chains (steptococci) or clusters (staphylococci)

Question 18

What is an example of a bacilli that forms rods?

Answer 18

Corynebacterium diphtheriae - ends stick together when dividing end up looking link chinese characters

Question 19

Bacterial cytoplasmic membrane

Answer 19

similar composition: 20-30% lipid & 60% prot

• contains oxidative enzymes for oxid. phosphorylation (acts like inner membrane of a mito)
• has cell wall synth prots
• has active transporters to uptake specific nutrients that are low in conc in bact’s dilute enviro
• has transporters to secrete

Question 20

What is the bacterial “equivalent” of a nucleus?

Answer 20

Bact has no true membrane-bound nucleus; has nucleoid instead which is name for region of the circular DNA

Question 21

bacterial ribosomes

Answer 21

smaller (70S vs. 80S) and susceptible to antibiotics that do not affect euk ribos

Question 22

Cyotplasmic granules

Answer 22

• visible on microscopy (EM?)
• contain lipid or glycogen
• can also contain metachromatic phosphate (e.g. in diptheria, helps ID this bact)

Question 23

Describe the components and structure of the cell wall.

Answer 23

Cell wall is made of up strings of NAG (N-acetyl-glucosamine) and NAM (N-acetyl-muramic acid) which have tetrapeptide side chains that vary among species. These glycosides (NAG and NAM) are held together by glycosidic linkages.

The strings are “cross-linked” by peptide bonds created between a.a.’s on NAM’s tetrapeptide side chains.

Question 24

Where is lysozyme produced? Mechanism?

Answer 24

• found in tears and other bodily fluids

- breaks glycosidic linkage between NAG and NAM—>digests cell wall of some bacteria (i.e. anti-bact agent)

Question 25

Are Gram + or Gram - more susceptible to disinfectants and antibiotics?

Answer 25

Gram +

Question 26

Gram (+) vs. Gram (-)

Answer 26

Gram (+): - thicker peptidoglycan cell wall - no outer membrane - no periplasmic spcae - some Gram(+)s' have cell walls also have teichoic acid (polysacc of ribitol phosph. or glycerol phosph) that are often antigenic - more susceptible to anti-microbials Gram (-): - thinner peptidoglycan cell wall - has 2nd, outer lipid bilayer - has periplasmic space - 2nd memb. covered in LPS (a.k.a. endotoxin) - less susceptible to anti-microbials

Question 27

Lipid A

Answer 27

component of LPS imbedded in the OM (outer memb.)

Question 28

porins

Answer 28

transmembrane pore proteins in the OM of Gram (-) bact; small molecules only (many antibiotics, e.g. vanco, too big)

Question 29

LPS components

Answer 29

polysacc-confersantigenic specificity; component that sticks out; outermost part is O-antigen Lipid A-confers toxicity; component imbedded in the OM (outer memb.)

Question 30

O antigen f(x)? Why?

Answer 30

O antigen is oligosaccharide at the distal end of the LPS whose sugar sequence **confers antigenic specificity** to Gram (-) bacteria because they predominate the cell's surface

Question 31

Degradative enzymes? How diff in Gram (+) vs. Gram (-)?

Answer 31

Degradative enzymes can break down large nutrients in external enviro (e.g. polysacchs or proteins) and also antibiotics (e.g. penicilinase) - Gram (+) secrete into external environment or tether them to their out cell wall - Gram (-) contain these in their special periplasmic space

Question 32

Gram Stain Procedure

Answer 32

``` 1. Crystal violet (1 min) WASH 2. Iodine to form complex w/ CV (1 min) WASH 3. Alcohol-based decolorizer (30-60 secs) WASH 4. Safranin counterstain (1 min) WASH BLOT DRY ```

Question 33

capsule

Answer 33

many bact don't have but those that do use this "loose slime" polysaccharide to resist phagocytosis -antibodies are made to target this and vaccines sometimes contain capsules/capsular components

Question 34

bacterial flagella components

Answer 34

made of flagellins in helical formation with open pore (as opposed to eukaryotic MT-based flagella)

Question 35

bacterial flagella f(x)

Answer 35

act like propeller; almost all motile bacteria have flagella

Question 36

flagella arrangements

Answer 36

polar flagella - only on one side | peritrichous flagella - all around cell

Question 37

pili and fimbriae; name specific types

Answer 37

basically same, just different size - hollow tubes of protein - sex pili - hold two bacteria together during conjugation - F pili - the bacterial penis - Type IV pili - allow bacteria to move around once bound to surface of a cell; aids in colony formation

Question 38

Which species make spores?

Answer 38

Those of genera Bacillus and Clostridia | -Examples: Bacillus anthracis and Clostridium tetani

Question 39

When are spores created?

Answer 39

In times of nutrient deprivation

Question 40

Chemotaxis mechanism

Answer 40

- bacteria employ chemoreceptive sensors in the membrane to control a phospho-cascade that in turn controls the mov't of flagella - when chemo-attracted: flagella rotate counter-clockwise —>str8 forward mov't - when chemo-repelled: flagella rotate clockwise and therefore tumble in place