Bacteriology Part 2

Question 1

Features that distinguish Prokaryotes/Eukaryotes (5)

Answer 1

1. A single circular chromosome instead of nucleus with multiple chromosomes
2. No nuclear membrane or mitotic apparatus
3. Transcription coupled to translation (70S ribosome)
4. Cell wall with unique residues
5. No endoplasmic reticulum, mitochondria or other organelles; bacteria have complex plasma membrane

Question 2

Eukaryotes

Answer 2

Sharp natural species boundaries - Species are defined by the ability to produce fertile offspring

Question 3

Prokaryotes

Answer 3

No sharp natural species boundary - Species defined by genetic relatedness and possession of similar physiological function

Question 4

Binary fission

Answer 4

Asexual multiplication, where each individual cell gives rise to two identical offspring

Question 5

Two ways of identifying prokatyotic species

Answer 5

Conventional

Molecular

Question 6

Two methods of molecular identification of bacteria

Answer 6

Hybridization techniques

Amplification techniques

Question 7

Amplification of pathogen specific DNA - PCR

Answer 7

• Identify slow growing - or - non-cultivable bacteria
• Rapid identification - amplify gene encoding difficile toxin from stool of an individual with antibiotic-associated pseudomembrane

Question 8

Difficile

Answer 8

Difficult to isolate and grow; due to extreme oxygen sensitivity of this organism

Question 9

Analysis of restriction endonuclease patterns of the bacterial chromosome

Answer 9

Restriction fragment length polymorphisms (RFLP) - Used during hospital acquired infections to determine the source of an infection

Question 10

Utility and Application of molecular diagnosis

Answer 10

Distinction of DNA from bacterial strains separated by pulsed field gel electrophoresis (RFLP)

• To determine whether an infection was community or hospital acquired

Question 11

Conventional Identification of a prokaryotic species determines:

Answer 11

Morphology - Cell shape, gram stain, motility - presence of capsule

Biochemistry - Ability to metabolize specific substrates - Production of specific end products - Antibiotic sensitivity

Question 12

Goal of conventional identification

Answer 12

Rapid Diagnosis of pathogens

Question 13

Response to O2

Aerobes:

Microaerophiles:

Facultative anaerobes:

Aerotolerant:

Anaerobes:

Answer 13

Aerobes: Metabolize O2; grow only in its presence

Microaerophiles: Metabolize O2; grow only in low O2

Facultative anaerobes: Metabolize O2 in the presence of O2; ferment in the absence

Aerotolerant: Do not metabolize O2; but ferment in the presence or absence of O2

Anaerobes: Do not metabolize O2; do not grow in the presence of O2 (gut bacteria)

Question 14

Oxidase Test

Answer 14

Differentiates aerobes from facultative anaerobes:

• Aerobes: use cytochrome C as the terminal oxidase
• Facultative anaerobes use cytochrome D as terminal oxidase

Question 15

Describe Anaerobic Respiration

Answer 15

• Unique to prokaryotes
• Occurs in the absence of O2
• Bacteria reduce NO3 → NO2 or N2
• NO3+ → NO2 → N2

Question 16

Fermentation Properties

Answer 16

• Permit the overall oxidation-reduction balance to be preserved (NADH2/NAD)
• Pyruvate is usually the electron acceptor
• Inefficient in energy generation

Question 17

Energy from respiration vs fermentation

Answer 17

Oxidation of Glucose: △G = -686 Kcal/mole

Fermentation to lactate: △G = -47 Kcal/mole (selective advantage in the environment)

Question 18

Mixed Acid Fermentation: Enterobacteriaceae

Describe the process

Answer 18

Question 19

Diagnostic test for enterobacteriaceae

Answer 19

Grow bacteria anaerobically in sugar and score for acid (yellow) and gas

Question 20

Properties of Bacterial growth

Answer 20

Lag - No cell division: Adaptation; Increased metabolism

Exponential - balanced growth

Stationary - decreased nutrients, △pH, builup to toxic products

Death - Eventual, slope varied with species

Question 21

Bacteria associated with oxygen

Answer 21

• Obligate anaerobes
• Aerotolerant anaerobes
• Facultative anaerobes
• Microaerophiles
• Obligate aerobes

Question 22

Temperature: Survival Range and Optimum Range

• Psychrophilic
• Mesophilic
• Thermophilic

Answer 22

Question 23

Pathogenic bacteria usually grow between pH ___ and ____

Answer 23

7.2 and 7.6

Question 24

Most bacteria only tolerate moderate salt concentrations; ______ are an exception

Answer 24

Halophilic - Require up to 30% salt for growth

Question 25

Selective media which utilizes osmotic sensitivity for selection of microbes

Answer 25

Mannitol salt media: 7.5% NaCl- selects for gram positive by inhibition of growth of gram negative

Question 26

What is the alternative life cycle achieved by some bacteria

Answer 26

Sporulation (vegetative cell)

Question 27

Sporulation

Answer 27

Unique property of a subset of bacteria

1. Bacillus (G + aerobe)
2. Clostridium (G + anaerobe)
3. Sporosarcina (G+ aerobe)

Question 28

Spore

Answer 28

Dormant structure capable of survival for prolonged periods; with capacity to reestablish the vegetative life style

Question 29

Spores are _______ to stains

Answer 29

Refractive

Question 30

Spore characteristics

Answer 30

• Spores may remain dormant for 100s of years
• Germination: Water and metabolite (amino acid; sugar)
• Mature spore is extremely resistant to heat
• To inactivate spores: Wet heat, 120°, 20 minutes