MIDTERM 2 Citrate Flashcards Preview

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Flashcards in MIDTERM 2 Citrate Deck (23):

What are heterotrophic microorganisms?

Those that depend on an outside source of carbon


What does the uptake and utilization of organic compounds require?

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


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

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


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

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


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

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


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

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


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



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



What bacterial mostly causes GI tract infections

Facultative gram negative rods


What two groups are enteric bacteria divided into?

1. Escherichia
2. Entero bacter


Where is Escherichia found?

Found in mammalian intestine


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

its a strong indication that theres fecal contamination


What is contrasting about entero bacter to escherichia?

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


Purpose of Citrate test?

It distinguishes between Enterobacter and Escherichia


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



how does Citrate test work?

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


Qualities of Citrate test and what it contains?

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


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

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


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

1. Some citrate will be removed from medium
2. Exhibit cell growth using citrate alone as energy source


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

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


Why cant Escherichia utilize citrate?

it lacks the ability to translocate the citrate.


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

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


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

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