MRS Medium , 200g

Description: 

MRS medium is selective for lactobacilli but some growth of leuconostocs and pediococci may occur. Selectivity can be altered by pH adjustment. Lactobacilli will tolerate lower pH levels than streptococci (pH 5.0-6.5) with pediococci and leuconostocs growing best within this range. Inhibitors of the main groups of competitor microflora inclu de thallous acetate, sodium acetate, sorbic acid, acetic acid, sodium nitrite, cycloheximide and polymyxin. These substances can be used at varying concentrations and combinations but, inevitably, a compromise has to be reached between selectivity and productivity of the organism(s) sought3. MRS Agar with sorbic acid has been described 3,4. This is MRS medium with its pH reduced to 5.7 and 0.14% sorbic acid added (equating to 0.2% potassium sorbate). 

An evaluation of media for selective enumeration of Lactobacillus acidophilus and Bifidobacteriumspecies showed that minor adjustments to the basic formula of MRS Agar can readily be made to optimise its performance for determining the content of Lactobacillus acidophilus and Bifidobacteriumspp. in the presence of other lactic acid bacteria which are present in yoghurt5. 

Lactobacilli are microaerophilic and generally require layer plates for aerobic cultivation on solid media. Submerged or surface colonies may be compact or feathery, and are small, opaque and white. 

Specification: 

200g