Answer:
In acid-fast staining, carbon fuchsin is used as a primary stain which dissolves the mycolic acid present in the cell wall of <em>Mycobacterium smegmatis </em>and penetrates through it which results in staining <em>Mycobacterium</em> red.
Staphylococcus aureus cell wall does not contain mycolic acid so carbon fuchsin does not penetrate its cell wall, therefore, it becomes colorless after destaining with acid alcohol.
After destaining step methylene blue is added to stain non-acid-fast bacteria blue. So if I mistakenly forgot to use methylene blue during the procedure <em>Mycobacterium smegmatis</em> will appear red due to carbon fuchsin present in their cell wall and S<em>taphylococcus aureus</em> will appear colorless because it is destained.
I think what they rely on is there experiment and how they do it
Nitrifying bacteria gets nitrogen from the air and turns it into nitrogen that is available for plant use. This can be seen in the nitrogen cycle which may be useful to you
