My bacteria is serratia marcescens and the test I am working on is nitrate reduction. I believe I would get a positive reaction, but i'm not sure if it would turn red after adding in the reagents or after adding in the zinc?
Bacteria Serratia marcescens is short and the shape is rod in appearence. It's growth is possible during aerobic and anaerobic condition.Being Gram negative it has a cell wall ( thin)covered with outer membrane which consist of lipopolysacchrides. The outer membrane helps to uptake the nutrients.
Identification of Bacteria Serratia marcescens -:
On Nitrate Reduction: it gives positive results with nitrate as it accepts the final electron and not oxygen. Serratia marcescens generally gives red stain.
The bacteria is covered in broth of nitrate and after 4-5 hours if Nitrate is reduced to nitrite and nitrite itself forms nitrous acid. When this nitrous acid reacts with sulfanilic acid gives diazotized sulfanilic acid . It gives red colour on treatment with alpha napthylamine indicating positive results of Nitrate Reduction.
On adding zinc in positive Nitrate Reduction , the red colour will not appear but it gives red colour with other reagent indicating the positive results of Nitrate Reduction.