Bacteriology - Background 3

Question 1

What is the optimum pH for bacteria to grow?

Answer 1

7. Although they can grow in pH 5-8

Question 2

What are the pH classifications for bacteria?

Answer 2

Acidophiles: below 5.5 (optimum 2 - 3.5)
Neutrophiles: 6-8
Alkalophiles: Above 8.5 (optimum 8.5 - 10)

Question 3

What is the difference between halophiles and facultative halophiles?

Answer 3

• Halophiles require NaCl for growth (includes many marine bacteria)
• Facultative halophiles can grow in the presence of salt but do not require it.

Question 4

Can staphylococcus aureus tolerate salt?

Answer 4

Yes, up to 20%

Question 5

How does microbial growth take place?

Answer 5

• Cell synthesizes new cell components and increases in size (metabolism)
• The number of cells in the population increases

Question 6

What is the mechanism of microbial growth?

Answer 6

Binary fission (2, 4, 8, 16, etc)

Question 7

What is generation time?

Answer 7

The time required for bacterial population to double in number. It is affected by environmental and physical factors (nutrient availability, build up of wastes)

Question 8

At which stage of the growth curve do you figure out what the generational time is?

Answer 8

Exponential growth phase

Question 9

At which stage in the growth curve have toxins started to accumulate?

Answer 9

Death phase

Question 10

What are the 2 steps generally done on special types of solid media to identify an organism?

Answer 10

1 - Isolation of the pathogen

2 - Obtain a pure culture so identification procedures/experiments can be carried out

Question 11

What are the different types of media?

Answer 11

• Nutrient/General purpose (grows everything, does not help you)
• Selective (selectively looks for certain pathogens)
• Selective and Differential
• Enrichment (you make the medium as rich as possible in order to entice some bacteria)

Question 12

What are the different types of hemolysis that blood agar can differentiate?

Answer 12

• Alpha hemolysis: partial (S. pneumoniae)
• Beta hemolysis: complete (S. pyogenes)
• Gamma hemolysis: none (E. faecalis)

Question 13

What is the colony forming unit formula?

Answer 13

CFUs/mL = # of colonies X dilution X 10

80 colonies X 100 X 10 = 80,000 CFU/mL

Question 14

Which is the most commonly used carbohydrate in carbohydrate catabolism?

Answer 14

Glucose. Other carbs, amino acids, and fats can also be used

Question 15

How is glucose catabolized?

Answer 15

• Cellular respiration (aerobic or anaerobic): produces CO2 and H2O
• Fermentation - produces organic waste products (acid, alcohol)
  Both processes begin with glycolysis