Physiology 429 



NUTRITIONAL REQUIREMENTS 

 OF PROTOZOA 



Pure cultures as material for research 



T 



HE ESTABLISHMENT OF various spccics in cultures free from 

 other inicroorganisms opened a new era in the study oi protozoan nutri- 

 tion, making possible for the first time a realistic approach to the deter- 

 mination of basal food requirements. As a result, the investigation of 

 metabolic activities in Protozoa is steadily expanding, and is leading to 

 increasingly precise interpretations. 



One of the important factors in this rapidly developing field has been 

 the availability of many phytofiagellates in pine culture. For this, much 

 credit is due E. G. Pringsheim^ whose unfailing determination was 

 resj^onsible for maintaining an invaluable collection intact through a 

 number of trying years. The phytofiagellates are particularly favorable 

 material for investigation because their absolute requirements are much 

 less extensive than those of higher Protozoa. Consequently, they afford 

 the most direct routes to the determination of mineral requirements, and 

 also the need for certain vitamins and organic foods. The relatively simple 

 requirements of certain phytofiagellates (Table 8. 1), in contrast to the 

 complex brews needed by higher I^rotozoa, also should expedite the study 

 of metabolic pathways. Furthermore, the diversity of phytofiagellates, with 

 respect to the j^ossession or lack of chlorophyll and the presence or absence 

 of holozoic habits, encourages consideration of the evolutionary and taxo- 

 nomic aspects of protozoan nutrition. 



Until recently, ciliates and Zoomastigophorea had been grown only in 

 broths of unknown chemical composition which endangered the validity 

 of conclusions concerning basal food requirements. The development of 

 almost completely defined media (Table 8. 1) for at least a few of these 

 higher Protozoa (121, 282, 349, 540, 568) insures much the same results 

 as those now obtainable with many phytofiagellates. 



Aside from the intrinsic interest to protozoologists, the study of pro- 

 tozoan nutrition promises significant contributions to the general fields 

 of biochemistry and physiology. In the study of plant nutrition, the rap- 

 idly growing chlorophyll-bearing flagellates are readily adaptable to the 

 investigation of various fundamental problems. The study of animal nu- 

 trition might be served in the same way by the typical animals among 

 the Protozoa. As microscopic animals, which approach bacteria in rates 

 of growth and ease of handling. Protozoa in pure cultures also offer ma- 



^ Pringsheim, E. G. 1946. Pure Cultures of Algae (Cambridge University Press). 



