Question

Question 5

Question text

You observe an oil spill in the Gulf of Mexico (GOM) and hypothesis that the indigenous microbial community in the soil will be able to degrade the alkane portion of the spill under sulfate reducing conditions. You set up multiple incubations under the following conditions and monitor the disappearance of sulfate over time. After 100 days of incubation the results are as follows:

1) The enrichment containing GOM sediment + oil + medium showed 99% depletion of sulfate

2) The enrichment containing GOM sediment + medium (no oil was added) showed 25% depletion of sulfate

3) The enrichment containing medium + oil (no GOM sediment was added) had 0% depletion of sulfate

4) The enrichment containing medium + oil + heat-killed GOM sediment had 0% depletion of sulfate

Select all the answers that could be a valid conclusion?

Select one or more:

a. The indigenous microbes have additional substrate to oxidize besides the alkanes under sulfate reducing conditions

b. The indigenous microbes are not metabolizing alkanes

c. The indigenous microbes are utilizing the alkanes without sulfate

d. The indigenous microbes in the GOM sediment will oxidize alkanes under sulfate reducing conditions

Question 6

Question text

Click all that are true concerning the use of an "unamended" controls:

Select one or more:

a. Shows that abiotic factors (chemical reactions) do not catalyze the same results

b. Will elucidate whether there are multiple carbon sources within the enrichment

c. The inoculum is heat-killed before incubation

d. Provides information about aseptic technique

e. Definitively proves that the metabolic process is linked to cell respiration

Question 7

Question text

Click all that are true concerning the use of an "uninoculated" controls:

Select one or more:

a. Shows that abiotic factors (chemical reactions) do not catalyze the same results

b. Provides information about aseptic technique

c. The inoculum is heat-killed before incubation

d. Will elucidate whether there are multiple carbon sources within the enrichment

e. Definitively proves that the metabolic process is linked to cell respiration

Question 8

Question text

Click all that are true concerning the use of a "sterile" controls:

Select one or more:

a. Shows that abiotic factors (chemical reactions) do not catalyze the same results

b. Will elucidate whether there are multiple carbon sources within the enrichment

c. The inoculum is heat-killed before incubation

d. Provides information about aseptic technique

e. Definitively proves that the metabolic process is linked to cell respiration

Answer 1

1. The correct options are

a - The indigenous microbes have the additional substrate to oxidize besides the alkanes under sulfate-reducing conditions. This is more relevant from Case 2 where there is still a basal 25% reduction in spite of no substrate addition. The substrate here is oil. So, that means, the microorganisms are still catabolizing alkanes which are present additionally but not in oil

d - The indigenous microbes in the GOM sediment will oxidize alkanes under sulfate-reducing conditions because in case 2, there is still 25% depletion and here sulfate-reducing medium is present. This means that only under the presence of sulfate-reducing conditions, the microbes degrade the alkanes. In case 3 and 4, there is 0% depletion as there is sulfate-reducing medium present, but no microbes present to degrade the alkanes

6. The correct options are:-
a - Shows that abiotic factors (chemical reactions) do not catalyze the same results as two different cases (Case 1 and 2) gives two different percentages of sulfate depletion. Had there been same result, we would have not selected this option.

e - Definitively proves that the metabolic process is linked to cell respiration as only those microbes will degrade the oil which can utilize the oil as a source of carbon for its growth.

b - Will elucidate whether there are multiple carbon sources within the enrichment as two different kinds of enrichment (Case 1 and 2) gave two different percentages. So, there has to be a different source of Carbon within these two enrichments. One carbon source is in the oil spill and the other is in the enrichment itself.

7. The correct options are:-

b - Provides information about aseptic technique as uninoculated control gave 0% depletion in sulfates (Case 3)

e - Definitively proves that the metabolic process is linked to cell respiration as without the presence of microbes, alkanes are not degraded (Case 3 has any microbes present)

8. The correct options are:-

e - Definitively proves that the metabolic process is linked to cell respiration as the sterile process (Case 4), where the microbes are heat-killed in GOM sediment show 0% depletion

c - The inoculum is heat-killed before incubation. In Case 4, the inoculum is heat-killed such that no microbe is left to degrade the oil and thus, shows 0% sulfate reduction.