Question

I have an unknown microbe. I am trying to determine if it is Micrococcus Luteus or Micrococcus Lylae. The only difference between the two is that M. Luteus is + for inorganic nitrogen growth while M. Lylae is - for inirganic nitrigen growth. Can someone please help me understand the importance of that result as I try to determine the identity of the microbe. If it helps, my unknown tested - for motility, is an oxygen aerobe, - for glucose, - for lactose, - for sucrose,- for mannitol, - for indole, - for MR/VP, - for Urease, - for H2S, + for gelatinase, - for citrate, - for nitrate to nitrite reduction, - for amylase, + for catalase, + for oxidase, and gamma lysis. Thank you!

Answer 1

The unknown microbe is Micrococcus lylae.
Because it gives negative result for nitrate reduction test. Nitrate test determines the production of an enzyme called nitrate reductase, which results in the reduction of nitrate to nitrite, not all microbes are capable of reducing the nitrate. Micrococcus Luteus is not capable of reducing the nitrate to nitrite but Micrococcus lylae is and hence this determines that the unknown microbe is Micrococcus lylae
Micrococcus lylae is a gram positive bacterium found in skin, dust, and water. It grows in tetrads, irregular clusters, and cubical packets of eight, and colonies are often brightly pigmented. They are strictly aerobic.
Both the organisms are non-motile and aerobes and mostly shows almost all the test similar like the test for glucose, lactose, sucrose, mannitol and motility. It also shows positive test for catalase.