Ask A Scientist© Biology Archive

Question:  A student scientist is looking for a method to induce lactose 
intolerance in E. coli bacteria.  Is there a suggestion for a method?
Thanks, Carolyn McPherson
 
Answer:  The prevailing wisdom among geneticists is that we cannot really
"induce" lactose intolerance so much a we can "select" or "screen"
for mutant bacteria that have become lactose intolerant.  The idea
is that mutations in particular genes do not occur as a response
to some evolutionary or selective pressure; rather, mutations just happen
randomly, and those that confer a growth advantage (in a particular
situation) will help the bacterium grow faster than its siblings.
In a previous session, I suggested one way to identify those
bacteria; to induce mutations, any of several mutation-causing agents might
be tried, including chemicals and UV light.  In fact, one
worthwhile experiment might be to see how various exposure to UV light
might yield increasing numbers of lactose-intolerant mutants.
For more details or discussion, you might write me directly
(S. Triezenberg).