Studies on improvements in the medium for Lactobacillus acidophilus in the assay for deoxyribonucleic acid.

Lactobacillus (Thermobacterium) acidophilus strain R-26 has been proposed as an assay organism for the determination of deoxyribonucleic acids (Hoff-J0rgensen, 1952). In attempting to use this organism for deoxyribonucleic acid determinations in our laboratory, it was noted that growth of the culture was very poor unless crude supplements, such as yeast extract or liver extracts, were added to the medium. The highly significant response observed with these supplements warranted further investigation. The unique requirement of L. acidophilus strain R-26 for a deoxyriboside which is not replaceable by vitamin B,2 also suggested that the use of this organism for further studies on nucleic acid metabolism would be extremely fruitful.