Microbiology question

Design an enrichment medium to isolate a detergent-degrading bacterium that is found in soil?

I would start by using soil that is sure to have the bacterium in it.

First, attempt to isolate the bacterium by exposing the soil to varying concentrations of detergent solution. By searching the lit, get a feel for the range of concentrations of detergent these critters handle best, then prepare solutions of varying concentrations, in this range, of the detergent and add to aliquots (measured divisions) of the soil. Do this with a range of differently prepared detergents, also.

This isn't strictly an enrichment medium because the bacterium may not be benefiting from the detergent per se, but rather a component of it (e.g. phosphorus).

So, after you've found which detergent concentration of which detergent yields the greatest population growth of this bacterium, examine the components of the detergent. If you can tease out all the constituents of the detergent down to to compound (enzymes, surfactants, etc) you can then expose the bacterium to them separately, in a range of concentrations (to ensure optimal exposure to the compound in question). Then, examine the growth success of each population in each solution (be sure to statstically analyze for significance using analysis of variance).

In this way you would identify exactly what component in the detergent is attractive/advantageous to the bacterium and be able to begin to devise an optimal enrichment recipe for them.