Abstract
By the well-known procedure of transferring cultures to media containing increasing concentrations of antibiotics, three variants of Streptococcus Faecalis, respectively resistant to 1, 000 units of penicillin (PN), 300γ of choloramphenicol (CM), or 250γ of tetracycline (TC) per ml., could be made after respective 27th, 111th, or 120th passage.They were proved almost identical with their sensitive parent strain in many of physiological properties such as catalase reaction, nitrate reduction, indole production, hemolysis, and so on. However, they differed from the parent strain in several points.They showed somewhat poorer growth and production of lactic acid. In nutrition, glycine was altered to stimulatory from non-essential, and serine, though only in the PN-resistant strain, was the same. The TC-resistant strain became to require vitamin B2 strictly, and the PN-resistant one did not demand folic acid. Each variant indicated a tendency of poor utilization in trehalose and dextrin, and further the TC-resistant variant did likewise in mannose and lactose, too.In serological aspect, all variants retained the similar antigenic specificity as that of the original strain.
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