Mingfei Shao <mfshao at gmail.com> writes:
> Any one can recommend me some COUNTERSELECTABLE MARKERS for a gram positive
> I know SacB is a common one for gram negtive bacteria and can lead to many
> useful application.
> However I am now studying a strain from Bacillus spp. is there any
> counterpart of SacB in gram positive bacterium?
You might want to check out the PheS mutant described by Peter Kast:
pKSS--a second-generation general purpose cloning vector for efficient
positive selection of recombinant clones.
Gene. 1994 Jan 28;138(1-2):109-14 PMID: 8125286
You probably would need to modify the gram+ version of pheS.
I found it was important to control the pH of the medium containing