Micro Unit 1: Bacterial Structure and Function 2

Question 1

Flagella

Answer 1

• long polymers of flagellin that protrude from cell wall
• corkscrew shaped
• rotate to propel bacterium forward
• NOT WHIPLIKE (that describes cilia)

Question 2

Bacterial ribosomes

Answer 2

70S

• good target for antibiotics:
• aminoglycosides attack small subunit, interfere w/ initiation and accuracy
• tetracyclines attack small subunit, transfer of tRNA+aa sets to ribosome
• macrolides attack rRNA of large subunit, elongation

Question 3

Spores (endospores)

Answer 3

• spore-forming bacteria can survive extreme environmental conditions
• spore formation triggered by nutrient depletion
• bacterial genome and some macromolecules are compressed into a thick spherical coat that can survive high temps, dehydration, antiseptics, abx
• when nutrients + H2O are plentiful, spore unpacks into normal bacterial form, normal metabolism + reproduction resume

Question 4

Bacterial reproduction

Answer 4

• binary fission, logarithmic growth under optimal conditions
• limited primarily by available nutrients

Question 5

Bacterial growth

Answer 5

Lag phase, log phase, stationary phase, death phase
Lag: bacteria sense new environment and upregulate gene products for growth (liquid is clear)
Log: rapid cell division, exponential growth (lightly clowdy)
Stationary: nutrient depletion, waste accumulation, growth slows (very cloudy)
Death phase: waste accumulation kills most bacteria (culture like garbage – sediment on bottom, pellicle on top, middle cloudy + chunky)

Question 6

Obligate aerobe

Answer 6

rely on oxygen for electron transport pathway

ex. M tuberculosis

Question 7

Obligate anaerobe

Answer 7

Lacks superoxide dismutase/catalase and pathways to regenerate enzymes that have been oxidized, use fermentation pathways to generate ATP

• die in the presence of oxygen
• ex. Botulism

Question 8

Facultative anaerobes

Answer 8

Have fermentation and electron transport pathways; use oxygen when available and fermentation when not
- ex. E coli

Question 9

Sugar metabolism

Answer 9

Facultatives and anaerobes break down sugar for ATP in the absence of O2 = fermentation

• not as efficient as electron transport but suffices for growth
• organic acids produced as waste (usually lactic or pyruvic)

Question 10

Quorum sensing

Answer 10

bacteria’s ability to sense its population density and adjust gene expression accordingly, allows bacteria to conserve energy and coordinate attack