Re: How does a microorganism being gram + or - effect spectrometery results?

The answer to this question really depends upon what conditions you are 
using for the growth experiment. Just being Gram + or Gram - shouldn't 
affect the growth rate, some G+ bugs grow very fast and others slow, 
likewise some G- bugs grow fast and others slow. So determination of growth 
rate would not be a way to distinguish between G- or G+ bugs. 

However you can determine fermentation or non-fermentation depending upon 
carbon source used (is it fermentable or not) and whether or not they are 
grown with sufficient oxygen. I would guess the experiment you are doing is 
to measure the growth rate using different nutrients, different carbon 
sources. this can be used to distinguish between bacteria, but in a species 
specific manner, not in a Gram + or Gram - specific manner. 

So the results you would expect to see will be dependent upon the precise 
growth conditions and type of medium you are using.