killing ovenight grown OP50

I wanted to know if we can kill a overnight grown OP50 using one of the antibiotics? i do not want to add the antibiotic to the
NGM medium. i want to kill the OP50 in LB broth itself. Which antibiotic would be ideal and at what concentration?
it would be of great help if you could provide me a reference for it too. thank u.


yes you can, OP50 are a very sensitive bunch of bacteria :’(;

Follow the thread of replies, very interesting what happens when someone mistakenly writes resistant instead of sensitive!! basically 30µg/mL does the trick…

But WHY would you want to when you can just as easily heat-kill them (think of the environment)?



Thank you. Theres a reason i do not want to use heat killed OP50. We had this discussion on one of the previous threads

Heat killing is something i am not sure of hence i wanted to kill the bacteria in LB broth itself. I cannot use UV bcoz i am using certain
drugs in my media. So antibiotic killing was the best option. how long do u think i should incubate with 30 ug/mL antibiotic for a
overnight grown culture to attain complete kill?


quoting my famous countryman, ‘ay there’s the rub’. The main reason I would stick with heat killing is because it does exactly what it says on the tin…the bacteria are dead. With antibiotic treatment, there’s no certainty that they all will be…unfortunately, the killing efficiency of antibiotics added to existing cultures is dependent upon several factors, all of which make it a messy and uncertain business (remember George Bush’s shock and awe?)

First, antibiotics are more effective against exponentially growing cultures than against stationary ones and in any one culture there will be both. Second, the effectiveness of an antibiotic will be diminished over time by countermeasures (enzymes and other proteins) coming from both the live and the dead bacteria. Third, the added concentration of antibiotic requires a careful assessment of the bacterial concentration and pH changes associated with the culture may diminish further antibiotic activity.

If it were the case that the use of heat-killed bacteria was questionable (which it isn’t) and the method used to produce heat-killed bacteria hugely problematic (which it isn’t), then, of course, I would say have a go with antibiotics. HOWEVER, you’ll need considerably more than 30µg/mL as the culture is already established and this has consequences when you add the concentrated bacteria to your worms (probably some bacteria still alive, antibiotic is still present, cell products likely still there etc.)

I would persevere with heat-killed bacteria.




u making a compelling argument and hence will retry my heat killing method. if it works well and fine, else i have to choose the
antibiotic. UV is out of question as i ll be adding drugs to the plate.


i repeated the damn thing and i m still stuck with the larval stages in heat killed bacteria. i killed the bacteria at two reported temperatures
: 65 C for 30 mins and 100 C for 10 mins. i have used 5 mL volume of overnight grown (16h) OP50 for heat killing. Killed them in a
glass test tube.
Heat killed bacteria are generally used in life span assays where worms are transferred to Heat killed bacteria at L4 stages.
Do u think it has something to do with the developmental factor? Now i am planning to just transfer the L4 stage worms onto
dead bacteria and see if it molts to adulthood.


Why can’t you seed the bacteria. UV kill them. Then add drugs to the plate? We UV kill bacteria all the time.


as long as the drug(s) in question are rel. low molecular weight then you could also try what avsamuelson suggests.