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The classical morphological appearance of Diplococcus pneumonute in artificial culture media is that of pairs of cocci. Short chains consting of 2 to 4 pairs of organisms, aranged linearly, are seen in young cultures. The length may vary with the serological type. Chains are relatively uncommon with Type I but are encountered frequently with Type III. It is not known if chaining in this genus is an expression of incomplete cell division or is related to the characteristics of the capsular integument. It was observed in this laboratory that the addition of sodium citrate to a mediumotherwise suited for the growth of the pneumococcus resulted in the organisms being found in chains rather than as isolated diplococci. Okamoto (1940) using quatemary ammonium compounds and Badger (1944) using ethanolamine observed like rsults. Similar effects upon other organisms have been recorded. Filamentous forms of Cloidum perfringens were produced by Webb (1948) by growing the organisms in a medium deficient in Mg++. Subculture of these organisms in a Mg++ rich medium caused a reversion to the normal form. This reversion could not be accomplished by the substitution of metallic ions other than Mg++. Studies on the morphology of organisms grown in a Mg++ deficient medium were extended by Webb (1949) to include other groups of organisms such as clostridia and gram positive aerobic bacilli. Shankar and Bard (1952) investigated C. perfringenm with respect to the production of filamentous cells in Mg++ deficient media and found that Ca++ played a role in the production of filaments even at optimal levels of Mg++ and other ions. The relation of trace element concentration to the change in morphology of D. pneumoniae was investigated to ascertain which ions were involved in this alteration and to relate morphology and growth to metallic ion concentration. MATERIAL AND METHODS

THE PRODUCTION OF CHAINS BY DIPLOCOCCUS PNEUMONIAE IN MAGNESIUM DEFICIENT MEDIA