Using pH indicator in agar plates
Posted 25 February 2012 - 02:13 PM
However, before I do the experiment, I was wondering what kinds of problems I can expect using bromocresol purple indicator in the MRS agar in terms of errors and practicality so I can minimise these problems.
I plan to use 0.025ml per litre.
Also, I've never used this indicator before so what can I expect in terms of the colour the agar will be when I add it to the plates? Will it be initially all purple and after incubation, there will be some yellow colonies signifying lactic acid bacteria?
Really really appreciate the help!
Posted 26 February 2012 - 06:07 AM
MRS doesn;t typically include bromcresol purple ( http://www.neogen.co...nfo/7543_PI.pdf ) though some http://www.ncbi.nlm....cles/PMC110601/ have used it in this context and at 0.03% (as gram % s not ml's). It's used at 0.025% in other media and that should work in MRS as well. Supplemented medium should be purple and colonies of bacteria producing acid from glucose should produce yellow zones - but you really should validate qualitatively and quantitatively with representative isolates.
Posted 26 February 2012 - 11:24 AM
Posted 26 February 2012 - 07:20 PM