biochemical pathway

[Joshua Mularella]

My name is Josh Mularella and I was giving an extra credit problem in my
microbiology class where I have to design an experiment to deduce the three
intermediates in a linear biochemical pathway that starts with threonine
and ends with isoleucine.  Is there anywhere on the web that explains
this?

I was thinking of inducing mutation in unknown bacteria and then replica
plating onto NA plates and isoleucine + plates.  But how do you detect
the intermediates?

Hope you can help,  

Josh Mularella