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A laboratory experiment on Nitrate Reduction and Denitrification, focusing on the role of bacteria in converting nitrate to nitrite and further to gaseous nitrogen compounds. Students are required to perform the experiment using three different bacterial cultures: Alcaligenes faecalis, Proteus vulgaris, and Pseudomonas aeruginosa. instructions on materials, reagents, steps, and possible results, as well as their interpretations.
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Objectives?
Materials needed per table: Nitrate broth tubes (4) 1 sterile Q-tip
Three pure cultures needed per table: Alcaligenes faecalis (negative) Proteus vulgaris (positive for nitrite) Pseudomonas aeruginosa (denitrifier) Each student takes responsibility to inoculate one of the nitrate broth tubes
Add 5 drops of nitrate reagents A ( dimethyl- naphthylamine) and B (sulfanilic acid) red color means nitrite present (+)
Add small pinch of Zinc powder red means nitrate was present. Why? And what is the meaning?
A. faecalis
Negative Control P. vulgaris^
P. aeru- ginosa
What do you do next?
A. faecalis
Negative Control P. vulgaris
P. aeru- ginosa
Table 16-2: Nitrate Utilization Patterns Pattern Nitrate Nitrite Gas Interpretation NO 3 NOT used present^ absent^ absent^ No nitrate reduction NO 2 produced absent^ present^ absent^ Nitrate reduction^ to nitrite Gas produced absent^ absent^
Produced and escaped
Denitrification (Nitrate reduction all the way to gas)
Step 1 Step 2
Step 1
Step 2