Based on the information provided in the chapter opener, which of the following

Question

Based on the information provided in the chapter opener, which of the following techniques would be most appropriate to determine possible substrates to use for enrichment of this novel group of Archaea if you have only an environmental sample containing the native community with which to work?

d. stable isotope probing (SIP) and flow cytometry with cell sorting

Hint 1. Enrichment

Enrichment techniques are designed to increase the proportion of a desired type of microorganism. To do this, the desired type has to grow and be able to out-compete other organisms present. Knowledge concerning the type(s) of substrates used and the activity distribution toward that substrate by the different cell types in the sample will be useful in determining enrichment conditions that might be appropriate.

Hint 2. Determination of types of substrates used

Which technique or techniques described in this chapter can be used to determine whether a specific carbon-containing substrate can be used by a particular organism? Which technique or techniques can be used to identify specific organism types in a mixed culture?

a. microradiography coupled with fluorescence in situ hybridization (MAR-FISH) using initial incubation with 14CO2 b. microradiography coupled with fluorescence in situ hybridization (MAR-FISH) using prior incubations with a variety of different 14C-labeled lipids, lipid components, proteins, or amino acids c. denaturing gradient gel electrophoresis (DGGE) and flow cytometry with cell sorting

d. stable isotope probing (SIP) and flow cytometry with cell sorting

Hint 1. Enrichment

Enrichment techniques are designed to increase the proportion of a desired type of microorganism. To do this, the desired type has to grow and be able to out-compete other organisms present. Knowledge concerning the type(s) of substrates used and the activity distribution toward that substrate by the different cell types in the sample will be useful in determining enrichment conditions that might be appropriate.

Hint 2. Determination of types of substrates used

Which technique or techniques described in this chapter can be used to determine whether a specific carbon-containing substrate can be used by a particular organism? Which technique or techniques can be used to identify specific organism types in a mixed culture?

Explanation / Answer

The answer is option c , DGGE and flow cytometry . MAR-FISH technique is unsuitable for environmental samples . Moreover, MAR-FISH technique is unable to detect Nirrogen and oxygen in the samples. Hence its use is limited. So option a and b are incorrect. Similarly , isotope labeling is also limited when performed alone . It should be coupled with secondary ion mass spectroscopy. Thus option d is incorrect. Denaturing gradient gel electrophoresis is suitable method for detecting environmental samples. It determines the nature of the species in the sample by detecting the 16S rRNA . So , this method is effective compared to other methods mentioned here. It is also more effctive when combined with PCR.

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