What is the shape and arrangement of streptococcus thermoplilus under microscope?
The identification of Str. thermophilus using biochemical tests is not as straightforward as one would wish. Phenotypic traits such as carbohydrate fermentation are not reliable when dealing with wild strains (see for example Botina, S. G., Trenina Yu, M. A., Tsygankov, D., Sukhodolets, V. V. 2007. Comparison of genotypic and biochemical characteristics of Streptococcus thermophilus strains isolated from sour milk products. Applied Biochemistry and Microbiology 43:598-603.). These workers presented data suggesting that it is preferable to use gene 16S rRNA sequencing data for the identification of wild strains.
Utilization of glucose, lactose and fructose by Str. thermophilus isolates is fairly typical in most studies. Fermentation of mannose, galactose, sucrose, maltose, melibiose, and raffinose is typically variable. Str. thermophilus strains cannot ferment esculin.
Growth in appropriate media containing sodium chloride can be helpful in identification. Most strains will grow in 2% salt, but not in 4%. Strains can be urease positive or negative.
I have found the use of a temperature of 45C and appropriate media helpful in their isolation.
There are several articles on my website (www.dairyscience.info) that might be helpful. You might also find the chapter “STARTER CULTURES | Importance of Selected Genera” available through my list of references of some help also.
I have also included further information on the isolation of this organism in the Questions Section on ResearchGate.
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