Interrelationships between ribose and desoxyribose components of nucleic acids.

LactobaciUus bifidus (Lactobacilus acidophilus ATCC 4963) was previously reported (Skeggs et al., 1949) to require for growth, in an otherwise complete medium, either vitamin B12, thymine desoxyriboside, or intact desoxyribonucleic acid (DNA). The growth of L. bidus in the presence of DNA was found (Skeggs et al., 1950)1 to be inhibited competitively by yeast ribonucleic acid (RNA). Subsequent investigations (Skeggs, Wright, et al., 1950) revealed that the purine ribose nucleotides, adenylic acid and guanylic acid, effectively replaced yeast RNA in preventing utilization of DNA by L. biJidus. Highly purified preparations of adenosine-3-phosphoric acid2 and adenosine-5-phosphoric acid3 were equally inhibitory. The isomeric adenylic acid described by Carter (1950)2 had little or no inhibitory activity. When vitamin B12 replaced DNA, inhibition with RNA or guanylic acid was not reproducible, but adenylic acid was somewhat inhibitory although less effective than it was in the presence of DNA. Through the courtesy of Dr. Waldo Cohn, samples of thymidylic acid, desoxyadenylic acid, desoxycytidylic acid, and desoxyguanylic acid (Volkin et al., 1951) were made available to us. Hypoxanthine and thymine desoxyribosides were provided through the courtesy of Dr. J. 0. Lampen. All the desoxyribonucleotides and the available desoxyribosides proved capable of replacing DNA or vitamin B12 in the nutrition of L. bifidus. The effect of RNA and the ribose nucleotides on the growth of L. bifidus in the presence of these compounds is the subject of this communication.