Litmus milk

{{Short description|Milk-based medium used to distinguish between different species of bacteria}}

Litmus milk is a milk-based medium used to distinguish between different species of bacteria.{{cite journal|first1=Elizabeth A. |last1=Schierl |first2= Donna J. |last2=Blazevic|title=Rapid Identification of Enterococci by Reduction of Litmus Milk|journal=Journal of Clinical Microbiology|volume=14|issue=2|pages=227–228|date=August 1981|pmid=6895080 |pmc=271939}} The lactose (milk sugar), litmus (pH indicator), and casein (milk protein) contained within the medium can all be metabolized by different types of bacteria.{{cite web |url=http://web.clark.edu/tkibota/240/Unknowns/LitmusMilk.htm#Introduction |title=Litmus Milk Results and Meanings |website=clark.edu}}

Early in the development of microbiology, milk was used as a convenient, rich growth medium for propagating bacteria. The litmus in the medium acts as both a pH indicator and a redox (oxidation-reduction) indicator. The test itself tells whether the bacterium can ferment lactose, reduce litmus, form clots, form gas, or start peptonization.{{cite web|url=http://www.pmlmicro.com/assets/TDS/455.pdf |title=Litmus Milk Medium Data Sheet |archiveurl=https://web.archive.org/web/20110715094437/http://www.pmlmicro.com/assets/TDS/455.pdf |archivedate=15 July 2011 |url-status=dead }}