Spontaneous Spectinomycin resistance ?

[the End]

Hello,

I am seeing a relatively high rate of acquisition of spectinomycin 
resistance in the E. coli strain I am working with (CSH20 from Miller's
old kit). It appears that all cells in a cuture are somewhat resistant,
and that 60 or so colonies will form from approximately 100 ul of 
competent cells spread on a plate.


Anyone else see this ? Any relevant knowledge of mechanisms ?

Thanks much,

E-mail copies of all posts,

Jim
J. E. Graham 
Biology and Chemistry Departments 
Indiana University Bloomington