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For each of the two sources, which selective media (PIA or R2A-Cu) is more restr

ID: 223215 • Letter: F

Question

For each of the two sources, which selective media (PIA or R2A-Cu) is more restrictive? By this I mean which selective media yields the lowest CFU/g compared to K2A. In the past we have observed that when we add a metal or irgasan to media we see fewer strains (CPUs) come up on the plates. We have interpreted this result to be the consequence of additional selection pressure that prevents the growth of strains (hat arc sensitive to metals or irgasan. Is this the case this year? Explain your observations with your data.

Explanation / Answer

When a metal or irgasan is added to a media, fewer strains are visible on the plates. This might be due to the additional selection pressure that prevents the growth of strains that are sensitive to the metal or the irgasan.

CFUs (Colony Forming Units) have maintained a still growth as observed from the graph. Though there is increase in the number of bacterial cells but not an impressive one. This is also the case this year but growth of strains have been prevented and with increase in the quantity of soil, the bacterial growth is same.