4 replies to this topic

[gyma]

hi there, i have a question about e coli. I want to clone a 2.5kb fragment into CSII-EF-IRES-GFP, after ligation, I transformed Dh5a. the clones grew very slowly, so I left the plate at 37c for a longer time than usual. when I got the plate out, colonies were big enough but around those there were so many very small colonies, very very small. I dont know what are those. could you tell me? I also want to know if i can still use this plate. thanks.

[perneseblue]

those small colonies are called satellite colonies. They appear because the colonies carrying the resistance gene has degraded the antibiotics in the surrounding medium. Which in turn allows, non antibiotic resistant  to grow up.. producing these satellite colonies.

[gyma]

perneseblue, on 06 April 2011 - 06:41 PM, said:

those small colonies are called satellite colonies. They appear because the colonies carrying the resistance gene has degraded the antibiotics in the surrounding medium. Which in turn allows, non antibiotic resistant  to grow up.. producing these satellite colonies.

thank you very much. so satellite colonies are not antibiotics-resistant,right? if i pick the "positive" colonies carefully and culture them in antibiotics-containing LB medium, can I rule out the possible contamination by satellite colonies? thanks.

[phage434]

That's right.

This problem occurs largely with ampicillin as the antibiotic.  Other antibiotics such as kanamycin don't exhibit this problem.

[gyma]

phage434, on 06 April 2011 - 07:12 PM, said:

That's right.

This problem occurs largely with ampicillin as the antibiotic.  Other antibiotics such as kanamycin don't exhibit this problem.

thank you.