451. Biochemical and serological properties of some citric acid fermenting streptococci from milk and dairy products

Abstract

1. Thirty-five strains of acetoin producing lactic streptococci isolated from raw milk, from starter cultures and from dairy products were investigated biochemically and serologically.2. The strains are shown to form a homogeneous unit, very similar toStrep. lactisO.J., which species they resemble in cultural behaviour, in growth-temperature range, in tolerance of sodium chloride and heat and in carbohydrate and other fermentations. They differ fromStrep. lactisessentially in their ability to utilize citrate in producing CO2volatile acids and C4-compounds (diacetyl, etc.). With few exceptions they bear no resemblance to the enterococci.3. Serologically the strains are shown to belong to group N and thus the relationship toStrep. lactisis clearly established.4. The strains investigated are shown to be identical withStrep. citrophilusvan Beynum & Pette and almost with certainty, though no direct comparison has yet been possible, withStrep. diacetilactisMatuszewskiet al.Probably they are identical, too, withStrep. diacetyl aromaticusKarnad andStrep. lactis aromaticusJoshi & Ram Ayyar.5. The taxonomic position of the relevant unit is discussed, and it is suggested that it be given species rank under the nameStrep. diacetilactis.