We would like to work with very short antibiotic resistance gene that are useable as selection marker in the bacteria Escherichia coli and potentially other Gram-negative strains. The shortest resistance gene that I know is the bleomycin resistance gene, which coding sequence is approximately 400 base pairs.
Does anybody know a shorter or equivalent size resistant gene useable in E. coli?
I think trimethoprim resistance genes can get extremely short. For example, the one on the linked plasmid has a coding sequence of 236 bp, and if you include the promoter it's potentially a whole antibiotic resistance cassette that's only ~300 bp long.
https://www.ncbi.nlm.nih.gov/nucleotide/284822054?report=genbank
Yes this is a good idea. The R67-like DHFR are pretty short. I did not think about them because I was thinking about selection on regular medium (e.g. LB).
I worked with trimethoprim antibiotic before. If I remember correctly they only work on minimal M9 medium right?
Trimethoprim selection works in LB pretty well actually if I'm remembering correctly, for cloning strains of E. coli, anyway. I've only used it for selection of R751 and RP4 plasmids though, so I don't know if there's any difference in how efficient it is between those DHFR gene cassettes and others.
Our preliminary results indicate that it's working. We are using 200 micro/ml trimethoprim in LB agar plates.
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