MIDTERM 2 Citrate

Question 1

What are heterotrophic microorganisms?

Answer 1

Those that depend on an outside source of carbon

Question 2

What does the uptake and utilization of organic compounds require?

Answer 2

1. Extracellular hydrolytic enzymes
2. binding proteins
3. Metabolic pathway
4. All the enzymes of that metabolic pathway
5. The genes

Question 3

Explain the significance of extracellularl hydrolytic enzymes for uptake and utilization of the organic compounds

Answer 3

They digest large polymeric molecules like polysaccharides, proteins, lipid, and nucleic acids –> then makes them into smaller monomers

Question 4

Explain the significance of binding proteins for uptake and utilization of the organic compounds

Answer 4

They are on the cell membrane
They transport proteins to bind
They move the substrate into the cell from outside
They are specific

Question 5

Explain significance of metabolic pathway for uptake and utilization of the organic compounds

Answer 5

They Accommodate the specific nutrient that has been transported into the cells

Question 6

Explain significance of Genes for uptake and utilization of the organic compounds

Answer 6

They code for proteins involved for each of the steps required for uptake and utilization of the organic compounds

Question 7

True or false:
It is possible for an organism to be able to digest and transport a nutrient into the cell but be unable to metabolize it

Answer 7

True

Question 8

True or False: an organism can be completely set up to metabolize a nutrient but lack some part of binding and transportation process

Answer 8

True

Question 9

What bacterial mostly causes GI tract infections

Answer 9

Facultative gram negative rods

Question 10

What two groups are enteric bacteria divided into?

Answer 10

1. Escherichia

2. Entero bacter

Question 11

Where is Escherichia found?

Answer 11

Found in mammalian intestine

Question 12

If there is Escherichia found in Water or food supply, what does it mean?

Answer 12

its a strong indication that theres fecal contamination

Question 13

What is contrasting about entero bacter to escherichia?

Answer 13

its found in other environmental samples and their presence cannot be taken as an indicator of fecal pollution.

Question 14

Purpose of Citrate test?

Answer 14

It distinguishes between Enterobacter and Escherichia

Question 15

Out of the two: escherichia and Enterobacter, which can utilize citrate?

Answer 15

Enterobacter

Question 16

how does Citrate test work?

Answer 16

it allows organisms to grow using citrate as its sole carbon source.

Question 17

Qualities of Citrate test and what it contains?

Answer 17

its a defined medium that contains
ammonium phosphate as nitrogen Source
Citrate as Carbon source
pH indicator

Question 18

What pH indicator does the citrate test use and whats its initial color and pH / End color and pH

Answer 18

Bromothymol Blue
Green at pH of 6.8 and
Dark Blue at pH 7.6 + ( indication of alkaline reaction)

Question 19

What would happen to the medium if an organism was capable of citrate uptake?

Answer 19

1. Some citrate will be removed from medium

2. Exhibit cell growth using citrate alone as energy source

Question 20

How does the pH indicator color change if an organism is capable of citrate uptake?

Answer 20

The organism ha a metabolic process that produces alkaline products which increases the pH of the medium and changes the color of the pH indicator to dark blue

Question 21

Why cant Escherichia utilize citrate?

Answer 21

it lacks the ability to translocate the citrate.

Question 22

What 2 factors does the end results of the citrate test depends on?

Answer 22

1. Presence / absence of growth

2. Presence / absence of a change in the medium color from green - dark blue

Question 23

How can we avoid a carry over of nutrient from the previous growth medium, ensuring that citrate is the only growth factor

Answer 23

Using a light inoculum of cells that have been diluted in sterile distilled water.