8 replies to this topic

[Abdullah]

Hi,

I have been making LB plates and putting (100mg/ml concentration of Ampicillin) 300microliters /300 ml agar.I have been experiencing e.coli growing in -ve as well as positive control.

My questions are:

What should be temperature of LB agar when adding ampicillin?.I suspect my ampicillin might not be working.
I follow all of protocol for the purpose.


Thank you

Abdullah

[phage434]

Ampicillin should be added at 55C or below.  This is roughly the temperature at which you can hold the bottle for 30 seconds and not want to drop it.  We typically set a water bath at 55 and leave the autoclaved agar there until we are ready to add antibiotics and pour the plates.   Don't forget to mix the agar after adding the antibiotics.  Do this gently to avoid forming excess bubbles.

[microgirl]

How old are your plates? With Amp I would use them within a week or two. You could also try upping your amp concentration to amp 150 or 200.

Abdullah, on Jun 1 2009, 02:46 AM, said:

Hi,

I have been making LB plates and putting (100mg/ml concentration of Ampicillin) 300microliters /300 ml agar.I have been experiencing e.coli growing in -ve as well as positive control.

My questions are:

What should be temperature of LB agar when adding ampicillin?.I suspect my ampicillin might not be working.
I follow all of protocol for the purpose.


Thank you

Abdullah

[Abdullah]

microgirl, on Jun 1 2009, 05:52 AM, said:

How old are your plates? With Amp I would use them within a week or two. You could also try upping your amp concentration to amp 150 or 200.

Abdullah, on Jun 1 2009, 02:46 AM, said:

Hi,

I have been making LB plates and putting (100mg/ml concentration of Ampicillin) 300microliters /300 ml agar.I have been experiencing e.coli growing in -ve as well as positive control.

My questions are:

What should be temperature of LB agar when adding ampicillin?.I suspect my ampicillin might not be working.
I follow all of protocol for the purpose.


Thank you

Abdullah

[Abdullah]

Hi,


my plates were a fresh.I used them after 1-2 hour of its preparation.I have made ampicillin in 1.5 vials today and trying it again.You mean to ampicillin concentration can be raised upto 150-200mg/ml with same quantity of ampicillim (300microliter/300 LB agar)

Ok I will test this as well.

Thank you

Abdullah

Abdullah, on Jun 1 2009, 05:56 AM, said:

microgirl, on Jun 1 2009, 05:52 AM, said:

How old are your plates? With Amp I would use them within a week or two. You could also try upping your amp concentration to amp 150 or 200.

Abdullah, on Jun 1 2009, 02:46 AM, said:

Hi,

I have been making LB plates and putting (100mg/ml concentration of Ampicillin) 300microliters /300 ml agar.I have been experiencing e.coli growing in -ve as well as positive control.

My questions are:

What should be temperature of LB agar when adding ampicillin?.I suspect my ampicillin might not be working.
I follow all of protocol for the purpose.


Thank you

Abdullah

[neuron]

if you add antibiotic at very high temperature, the antibiotic gets degrade, thats why as phage434 said it should be added at the optimum temperature, we also follow the same thing. But ampicillin is anyways very unstable thereby we don't use it, we use carbenicillin and that too we use only 50ug/uL.

[Abdullah]

Thank you very much amj2.


Kind Regards,

Abdullah

amj2, on Jun 6 2009, 04:19 AM, said:

if you add antibiotic at very high temperature, the antibiotic gets degrade, thats why as phage434 said it should be added at the optimum temperature, we also follow the same thing. But ampicillin is anyways very unstable thereby we don't use it, we use carbenicillin and that too we use only 50ug/uL.

[HomeBrew]

amj2, on Jun 6 2009, 08:19 AM, said:

if you add antibiotic at very high temperature, the antibiotic gets degrade, thats why as phage434 said it should be added at the optimum temperature, we also follow the same thing. But ampicillin is anyways very unstable thereby we don't use it, we use carbenicillin and that too we use only 50ug/uL.

I have used carbenicillin where the organism requires it (such as in Pseudomonas), but ampicillin is not so unstable that it can't be used for routine purposes like selection in E. coli (we use ampicillin at 100 ug/ml).  Carbenicillin is much more expensive than ampicillin; using it where it's not needed is wasteful...

[Abdullah]

Thank you HomeBrew for your guidline and comments.


Regards

HomeBrew, on Jun 7 2009, 08:44 AM, said:

amj2, on Jun 6 2009, 08:19 AM, said:

if you add antibiotic at very high temperature, the antibiotic gets degrade, thats why as phage434 said it should be added at the optimum temperature, we also follow the same thing. But ampicillin is anyways very unstable thereby we don't use it, we use carbenicillin and that too we use only 50ug/uL.

I have used carbenicillin where the organism requires it (such as in Pseudomonas), but ampicillin is not so unstable that it can't be used for routine purposes like selection in E. coli (we use ampicillin at 100 ug/ml).  Carbenicillin is much more expensive than ampicillin; using it where it's not needed is wasteful...