Abstract

CONTENT ALERTS Receive: RSS Feeds, eTOCs, free email alerts (when new articles cite this article), more» Information about commercial reprint orders: http://jb.asm.org/site/misc/reprints.xhtml To subscribe to to another ASM Journal go to: http://journals.asm.org/site/subscriptions/ MORRISON ROGOSA AND JOYCE A. MITCHELL National Institutes of Health, National Institute of Dental Research, Bethesda, Maryland Received for publication October 13, 1949 Usually colonial variation is considered from the point of view of smooth (S) to rough (R) variation. This variation may be accompanied by changes in (1) chemical constitution of the cell, such as loss of polysaccharide or other component; (2) antigenicity associated with a specific structure of the cell, e.g., polysaccharide or flagella; (3) virulence; and (4) miscellaneous factors. This report concerns itself with a change from R to S, rather than with the more conventional S to R variation. Evidence will be presented to show (1) that the R to S shift of the total population can be induced at will; (2) that the change is not permanent; (3) that the reverse S to R change of the total population can be controlled; and (4) that the results described cannot reasonably be .ttributed to mutation. EXPERIMENTAL METHODS Cultures. The organisms for which