A Study of the Effect of Penicillin and Dihydrostreptomycin on Protozoa with Special Reference to the Problems of Bacteria-Free Culture and Speciation in Euglena

Among the many phenomena observed in studies with streptomycin and penicillin, the apparent resistance of certain protozoa to antibiotics is of interest to the protozoologist. If this resistance exists in the case of all protozoa, then it should be possible to develop a technique involving antibiotics which can be used for obtaining bacteria-free cultures of any protozoan. The concentrations of penicillin and streptomycin used by various authors in attempts to effect isolation of specific protozoans are presented in Table 1. Speaking of sensitivity of bacteria to streptomycin, Waksman (1949) states that within genera, the.re is considerable variation in susceptibility to streptomycin between species;” It follows then, that such variations may exist within the many genera of Protozoa and possibly within the genus Euglena. If such is the case, these variations between Euglena species may be valid taxonomic characteristics to add to those already in use in species determination. The purpose of the present study is to: (1) determine if streptomycin and penicillin can be used to effect bacteria-free cultures of Euglena, (2) determine whether or not differences in sensitivity to streptomycin and penicillin exist among certain species of Euglena and if these variations can be used as valid diagnostic characteristics for speciation. Table 1 lists individuals who have worked with antibiotics attempting to obtain bacteria-free cultures of protozoans