Introduction to Bacteria

Question 1

Major structural features of bacteria (general)

Answer 1

1. cell wall 2. characteristic shape 3. characteristic cell surface structures 4. 70S Ribosome 5. Nucleoid

Question 2

Functions of external cell wall

Answer 2

1. resisting osmotic lysis 2. maintaing cell shape

Question 3

General structure of peptidoglycan layer

Answer 3

polymer w/repeating units of hexose sugars (GlcNAc & MurNAc) linked to tetrapeptide chains w/bacteria-specific amin acids (meso-DAP, D-glutamic acid, & D-alanine); peptidoglycan chains cross-link

Question 4

Gram-negative vs. Gram-positive peptidoglycan layer

Answer 4

1.Gram-negative=thin, sparsely cross-linked 2. Gram-positive=thick, cross-linked++, w/teichoic acids

Question 5

Composition of OM of gram-negative bacteria

Answer 5

lipid bilayer=lipopolysaccharide (LPS) + lipoproteins (covalent link to peptidoglycan) + porins + phospholipids

Question 6

Function of OM of gram-negative bacteria

Answer 6

1. barrier to entry of some anitbiotics 2. protects against detergents/toxins

Question 7

LPS of gram-negative bacteria structure

Answer 7

LPS=Lipid A (endotoxin component) + core poly sacc + oligosaccarachide (O antigen)

Question 8

Teichoic acid structure

Answer 8

TA=repeating polyglycerol-P or polyribitol-P backbone w/some substitutes covalently linked to peptidoglycan

Question 9

Capsule structure and fxn

Answer 9

1. outer surface layer of complex polysaccharides 2. enhance virulence by resisting phagocytosis

Question 10

Flagella structure and fxn

Answer 10

1. appendages originating in cytoplasmic membrane, composed of cytoskeleton elements. 2. molitily/chemotaxis

Question 11

Pili structure and fxn

Answer 11

1. protein, hair-like structure on surface 2. adherence to surfaces and tissues 3. sex pili–>bacterial conjugation

Question 12

Cytoplasmic membrane structure and fxn

Answer 12

1. lipid bilayer=phospholipids+proteins 2. physiological barrier btwn inside and outside of cell 3. selective permeability 4. electron transport system 5. transport metabolites 6. biosynthesis 7. DNA replication 8. flagellar rotation

Question 13

Nucleoid structure

Answer 13

1. distinct region of cytoplasm=location of tightly coild DNA; no nuclear membrane

Question 14

Types of DNA present in bacteria

Answer 14

1. Chromosome=double-stranded, circular DNA 2. Plasmid=extra-chromosomal, self-replicationg DNA, often encode virulence factors

Question 15

Bacteriophage definition

Answer 15

viruses that infect bacteria; genomes may incorporate into bacterial chromosome; change in phenotype=”phage conversion”

Question 16

Phases of bacterial growth (4)

Answer 16

1. lag phase 2. exponential phase 3. stationary phase 4. death phase

Question 17

Characteristics of lag phase

Answer 17

incolum=period of physiologic adjustment; establish enzymes/intracell enviro for growth on new medium

Question 18

Characteristics of exponential phase

Answer 18

growth rate proportional to cell number/mass; generation time=doubling time (time required to double cell number/mass)

Question 19

Characteristics of stationary phase

Answer 19

essential nutrients consumed and toxic metabolites acumulate; cell growth slows or stops; most bacteria in nature

Question 20

Characteristics of death phase

Answer 20

number of viable bacteria decrease over time; autolysis occures

Question 21

Minimal requirements for bacterial growth

Answer 21

1. certain inorganic ions 2. carbon source 3. energy source

Question 22

heterotrophic bacteria definition

Answer 22

bacteria that require organic carbon source (most bacterial pathogens)

Question 23

autotrophic bacteria definition

Answer 23

bacteria that obtain carbon exclusively from CO2

Question 24

fastidious bacteria definition

Answer 24

lacking in one+ biosynthetic pathways; require growth factors

Question 25

Strict Aerobic bacteria (1. Aerobic growth? 2. Anerobic growth? 3. Example)

Answer 25

1. + 2. - (Requires O2; cannot ferment) 3. mycobacterim tuberculosis

Question 26

Strict Anaerobic bacteria (1. Aerobic growth?2. Anerobic growth? 3. Example)

Answer 26

1. - 2. + (Killed by O2; ferments) 3. Clostrium or Bacteroides sp

Question 27

Aeritolerant anaerobic bacteria (1. Aerobic growth? 2. Anerobic growth? 3. Example)

Answer 27

1. + 2. + (Ferments w/ or w/out O2 present) 3. Streptococcus pyogenes

Question 28

Facultative Anaerobic bacteria (1. Aerobic growth?2. Anerobic growth? 3. Example)

Answer 28

1. + 2. + (Respires w/O2, Ferments w/out) 3. E. Coli or Staphylococcus aureus

Question 29

Microaerophilic bacteria (1. Aerobic growth?2. Anerobic growth? 3. Example)

Answer 29

1. + 2. ++ (Grows best at low O2, can grow some w/ or w/out O2) 3. Campylobacter jejuni

Question 30

2 types of "energy currency" in cells

Answer 30

1. ATP 2. electrochemical gradients/proton motive force

Question 31

Fermentation definition

Answer 31

organic compounds=electron donors and acceptors; no net oxidation of substrates

Question 32

Respiration definition

Answer 32

generation of ATP through electron transport w/O2 as final electron acceptor

Question 33

Selective toxicity definition

Answer 33

selective inhibiton of microbial growth at drug concentrations tolerated by the host; principle on which antimicrobials work

Question 34

Major categories of antimicrobial targets (5)

Answer 34

1. Cell wall-active antimicrobials 2. Outer/cytoplasmic membrane-active antimicrobials 3. Inhibition of protein synthesis 4. Inhibition of nucleic acid synthesis 5. Metabolic inhibitory antimicrobials

Question 35

Antibiotics w/cell wall target

Answer 35

1. B-lactams (penicillins, cepalosporins) 2. Vancomycin 3. Cycloserine

Question 36

Antibiotics w/cytoplasmic membrane target

Answer 36

Polymyxins

Question 37

Antibiotics w/protein synthesis target

Answer 37

1. Aminoglycosidase (streptomycin, kanamycin, etc.) 2. Tetracyclines 3. Chloramphenicol 4. Macrolides & Lincomycins

Question 38

Antibiotics w/DNA synthesis target

Answer 38

1. Quinolones 2. Rifampicin

Question 39

Antibiotics w/metabolic target

Answer 39

1. Sulfonamides 2. Trimethoprim 3. Isoniazid 4. Metronidazole

Question 40

Sulfonamide target/action

Answer 40

strucutral analog of p-aminobenzoic acid --> inhibits folic acid synthesis --> inhibits nucleic acid synthesis

Question 41

Trimethoprim target/action

Answer 41

inhibits dihydrofolate reductase --> inhibits folic acid synthesis --> inhibits nucleic acid synthesis

Question 42

Isoniazid target/action

Answer 42

inhibits lipid synthesis in mycobacteria

Question 43

Metronidazole target/action

Answer 43

interferes w/anaerobic metabolism

Question 44

anaerobic respiration definition

Answer 44

ATP generation via electron transport w/inorganic substrates as terminal electron acceptors