In article <YjHZV1600iV3A7KG9W at andrew.cmu.edu> Qian Ouyang,
qo22+ at andrew.cmu.edu writes:
>>I have a mutant strain that gives high B-gal activity in liquid culture,
>but, it shows white color on B-gal plate assay. Does anyone have the
>same experience? What would be the answers? Thanks.
We have found that a rho mutation (impaired mitochonrial function) will
produce white colony color, despite strong B-galactosidase activity
detected in lysates prepared from liquid culture. It has been suggested
to me that a rho mutation alters intracellular pH, and the E coli lacZ
gene is sensitive to pH. Strong buffers are usually included for the in
vitro assay of B-galactosidase, and thus overcome the altered
BTW, a strain with a rho mutation will not grow on glycerol medium.