Bact. Strain BL21

ChenHA hachen at bc.ic.ac.uk
Mon Mar 15 14:09:35 EST 1999

On Fri, 12 Mar 1999, Dr. Duncan Clark wrote: 

> In article <36E8D952.D67B5B58 at nmr.kun.nl>, Jan Aelen
> <janal at nmr.kun.nl> writes >Can anyone tell me, wich reason there is
> in some countries to forbid for >the future the Bacterial Strain
> BL21 and to prefer for this the strain >HMS174. 
> I believe that BL21 is derived from a wild type B strain. It could
> therefore populate the gut. For that reason alone it is considered

Something wrong somewhere surely.  All E. coli strains are
ultimately derived from wild-type strains, therefore it is wrong to
say that BL21 being derived from wild-type B strain is the reason
for it to be consider unsafe.  I ask a similar question some time
back because the Health and Safety people got a bit zealous and
suggested that BL21 should be consider unsafe.  If I remember
correctly, according to the Health and Safty booklet, the reason
BL21 should not be used because a) it is not derived from K and B
strains, b) it is not sufficiently disabled.  The first reason is
certainly wrong, because BL21 is derived from B strain.  However,
the second reason is certainly correct.  Unlike other commonly used
strains, BL21 is not rec- or have significant mutations that would
render it uncompetitive in natural environment.  I believe this
health and safety rule applies to all UK institutions, but how
zealously it is applied depends on the individual institution (there
is also this rather complicated point system I think on calculating
how hazardous an organism is, and some people get round this by
fudging the various parameters and get BL21 down to within the safe

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