kanamycin resistance

David Alexander dc.alexander at utoronto.ca
Tue Mar 27 10:46:29 EST 2001

Hello All,

I am working working with two kanamycin resistant plasmids
(i.e. both encode an aminoglycoside 3'-phosphotransferase (APH)) 
The plasmids have the same origin of replication (low copy, approx. 5 per cell)
but one includes the APH I from Tn903 (also found in pACYC177)
the other  APH II from Tn5.

Although I am electroporating into the same batch of competent bacteria
and plating on the same batch of media (final kan conc. 25 uL/ml)
Cells transformed with the APH I - containing plasmid grow faster than
cells transformed with the APH II - containing plasmid.
A BLASTP query indicates that the APH I and APH II proteins are similar,
but certainly not identical.

Does anyone have practical experience (or know of published reports)
with respect to these differences?
For example, should I reduce my kan concentration when using APH II?
Allow for a longer incubation before plating?
Also, do the APHI and APH II exhibit differences in neomycin resistance?

Thanks for any insight,


dc.alexander at utoronto.ca
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