Question

Below are results of the Ames Test that was conducted to determine whether a compound called sodium azide could be useful for causing detrimental mutations in bacteria, thus preventing bacterial growth on surgical tools. To test the mutagenicity of sodium azide, the Ames test was carried out. The bacterial species Salmonella typhimurium requires Histidine to grow and was plated on minimum growth plates lacking histidine. Bacteria plated on the control plate had only buffer added, while bacteria on the treatment plates had varying concentrations of sodium azide.

Negative control (No sodium azide) +Sodium Azide ( + Sodium Azide (5 μg/plate)

a. In your opinion, is sodium azide a good bacterial mutagen that could be successfully used to kill bacteria during surgical tool cleaning? Explain your reasoning.

b. The researchers who conducted this Ames test on the effects of sodium azide did not include the rat liver extract. Why not?

Answer 1

a.In this experiemnt, the control lacked sodium azide and histidine and the experimental plates too lacked histidine but had 1ug and 5 mg sodium azide respectively.Observations from the plates show that the number of colonies in the experimental plates is more than the control plates which means sodium azide is good bacterial mutagen. This is because Salmonella typhimurium requires histidine to grow but they themselves cannot produce histidine(also known as auxotrophic mutations) .In presence of sodium azide,mutations takes place that convert the bacteria into a phototrophic state such they they can produce their own histidine and thus are able to grow.Also, with an increase in the concentration of sodium azide ,the number of colonies observed are also more i.e experimental plate with 5 ug of sodium azide shows more colonies than the plate with 1ug of sodium azide. Thus , we can conclude that sodium azide a good bacterial mutagen that could be successfully used to kill bacteria during surgical tool cleaning.

b.The researchers who conducted this Ames did not include the rat liver extract because Salmonella typhimurium is a prokaryote and its metabolism is not the same as in mammals.Rat liver is used to copy the metabolic conditions in mammals.Rat liver extract contains liver enzymes that take part in metabolic porcesses in the liver.It is added  to study the metabolism of the chemical compound and to find out if compound itself is a mutagen or the metabolic products that is formed are mutanegic.