In article <01bbb38f$3e926f60$8c91fccc at ------>, "Takbum Ohn"
<ahnss at hitel.kol.co.kr> wrote:
> Hello!! netters...
>> I have cloned a cell wall hydrolase (probably toxic to E. coli host) from
> Moraxella sp. and now, I subcloned the insert as short as 1 kb.
>> The subclone expressed the gene very highly but, oddly, the copy of the
> subclone plasmid became very low.
>> I don't know what make my plasmid like that.
>> The mother plasmid is pT7T3 19u, a high-copy number phasimid vector.
You said the product of your cloned gene was toxic to E. coli...so I would
guess the subclones you isolated were plasmids with mutant (low) copy
number. E. coli probably cannot survive if expression is from a high copy
number plasmid in this instance.