5.8 - Growth of Bacteria

Question 1

Define Colony

Answer 1

Population of cells arising from a single cell of endospore, or from a group of attached cells.

Question 2

Define pure culture

Answer 2

Only one species or strain of bacteria

-Aids in ID by characteristic colony color, shape, texture, size

Question 3

Define mixed culture

Answer 3

Multiple strains or species of bacteria

Question 4

Explain Obligate Aerobes oxygen use and if they have SOD and Catalase

Answer 4

Have both SOD and Catalase

Example: Mycrobacterium tuberculosis

Question 5

Explain Facultative anaerobes oxygen use and if they have SOD and Catalase

Answer 5

have both SOD and Catalase

Example: Escherichia coli

Question 6

Explain Microaerophiles oxygen use and if they have SOD and Catalase

Answer 6

• Damaged by normal atm. levels O2 levels (above 20%), needs 2-10% O2 levels
• Usually has SOD and Catalase in very low concentrations
• Example Helicobacter pylori

Question 7

Explain Obligate/Strict anaerobes oxygen use and if they have SOD and Catalase

Answer 7

Usually lack both SOD and Catalase

Example: Clostridium

Question 8

Explain Aerotolerant anaerobes oxygen use and if they have SOD and Catalase

Answer 8

• Ignore O2
• Usually have SOD and lack Catalase
• Example: Propionibacterium acnes

Question 9

Superoxide Dismutase oxygen derivatives reaction equation

Answer 9

2 (02) + 2H –> O2 + H202

Question 10

Catalase oxygen derivatives reaction equation

Answer 10

2 H2O2 –> 2 (H2O) + 02

Question 11

Define Fastidious

Answer 11

If the bacteria requires many micronutrients or growth factors, they are considered fastidious

Question 12

Define Complex media

Answer 12

Supports growth of wide variety bacteria

-Example nutrient agar

Question 13

Define Enriched media

Answer 13

Addition of sterols, blood, serum, serum, egg yolk

Example: Sheep blood agar, Chocolate agar

Question 14

Sheep blood agar used for?

Answer 14

Most clinically important Gr+ and Gr-

Question 15

Chocolate agar used for?

Answer 15

• Heated lysed blood

- Fastidious organisms such as Neisseria gonorrhoea or Haemophilus influenzae

Question 16

Define Selective Media

Answer 16

Ingredients that inhibit growth of some organisms but allow others to grow

Question 17

Mannitol Salt Agar (MSA)

Answer 17

• High Concentration of NaCl (7.5%)
• Inhibits growth of most organisms but permits staphylococci to grow.
• Yellow color on altar indicates the bacterial species can ferment mannitol.

Question 18

MacConkey agar

Answer 18

• Bile salts, dye crystal violet
• Inhibits growth of gram positive bacteria and selects for gram negative (but not fastidious gram negative)
• Lactose fermenters and pH indicator, allows for differentiation of Gram negative based on their ability to ferment lactose (turns pink for lactose fermentors)

Question 19

What are the four stages of the bacterial growth curve?

Answer 19

Lag, Log, Stationary, and Death phases

Question 20

Define Lag phase of bacterial Growth curve?

Answer 20

Cells synthesizing new macromolecules

Question 21

Define Log phase of Bacterial Growth curve?

Answer 21

• Cell growing and dividing at maximal rate possible given their genetic potential and the local environment.
• Dividing and doubling at regular intervals.

Question 22

Define Stationary Phase?

Answer 22

• Total number of viable cells remains constant.
• Nutrient limitation, accumulation of toxic wastes, depletion of O2.
• Endospore formation
• Secondary metabolite synthesis. e.g. toxins, antibiotics

Question 23

Define Death Phase?

Answer 23

Decrease in number viable cells often exponential

Question 24

What is the best phase for harvest of useful products in the bacterial growth curve?

Answer 24

Stationary phase

Question 25

Which phase in the bacterial growth curve is the least resistant to antibiotics?

Answer 25

Stationary phase

Question 26

What phase in the bacterial growth curve is the most sensitive to antibiotics?

Answer 26

Log/Lag

Question 27

What phase is has the most DNA replication?

Answer 27

Lag phase

Question 28

What phase involves the plasma membrane?

Answer 28

Log phase

Question 29

What is the primary way that bacteria get cellular energy?

Answer 29

Oxidizing carbs.

-Glucose is the most common carb, proteins and lips can also be used.

Question 30

What are the main to ways to get energy from carbohydrates?

Answer 30

Cellular respiration and fermentation

Question 31

Which method of anaerobic bacteria of medical importance use what method of energy production?

Answer 31

Fermentation

Question 32

Define Glycolysis

Answer 32

• Any metabolic process that releases energy from a sugar or other organic molecule, does not require O2, (but can occur in the presence of O2) or an electron transport system, and uses an organic molecule as the final electron acceptor
• Does not use Krebs cycle or E.T.C.

Question 33

Main points of Prokaryotic anaerobic respiration?

Answer 33

• Energy generating mode for some anaerobic bacteria
• Inorganic compounds other than O2 serve as final acceptors (Ex: Nitrate)
• Can be used as an alternative to aerobic respiration in facultative organisms.
• Yields less energy than aerobic respiration.

Question 34

How many ATP molecules are produced during fermentation?

Answer 34

1) 1-2 ATP

2) Most energy from starting material remains in bonds of organic end products… thus not completely oxidized.

Question 35

Define Biofilm as a virulence strategy?

Answer 35

1) Antibiotic-resistance strategy
2) 65-80% human infections developed countries
3) Examples: Caries, gingivitis, periodontitis, otitis media, sinusitis, prostatitis, native valve endocarditis, chronic Pseudomonas aeruginosa infections in cystic fibrosis, catheter/shunt infections, heart valve/prosthetic implant infections

Question 36

What is planktonic phenotype?

Answer 36

‘Free floating’, may be motile

Question 37

What changes to the bacteria happen once a biofilm is formed?

Answer 37

• Attached to a surface, loss of flagella.

- They are sticky, slimy, and tenacious.

Question 38

Are biofilms made of only one type of bacteria?

Answer 38

No, they are mixed, heterogeneous, dynamic, slime covered cities.