A Method for Producing Increased Carbon Dioxide Tension in Individual Culture Tubes and Flasks.

During the past few years there has been a growing appreciation of the role of carbon dioxide in bacteriology. It has been demonstrated by a number of observers that the presence of carbon dioxide is apparently necessary for growth of all species of bacteria so far studied. Walker (1932) and Gladstone et al. (1935) suggest that the lag phase of the bacterial growth cycle is due to the failure of bacteria to multiply until a certain minimum amount of carbon dioxide is produced in the culture by their activities. If this is correct, it would appear that carbon dioxide should be supplied to cultures of feebly-growing organisms and to cultures in which the inoculum is small such as, for example, single cell cultures. Since the size of the inoculum, in terms of the number of bacterial cells, is not usually known when cultures are made from exudates, blood or other materials from suspected cases of disease, it follows that the routine provision of increased carbon dioxide tensions in such cultures would be desirable. The use of increased carbon dioxide tensions has been recommended, especially for isolating gonococci, meningococci and Brucella aborts. A number of investigators, including McLeod and his associates (1934), Leahy and Carpenter (1936) and Thompson (1935) have demonstrated the value of incubating cultures for the isolation of gonococci from suspected cases in an atmosphere containing about 10 per cent CO2. Cohen and Flem-