Studies in the Respiration of Paramecium Caudatum

ABSTRACT The lack of specific enzyme studies on protozoan material may be attributed mainly to manipulative difficulties. Burge & Williams (1927), in their substrate-utilization study on Paramecium caudatum, stated the position as follows: ‘The most difficult part of this investigation was the raising of these organisms in sufficiently large quantities and in fairly pure cultures.’ The slow advance of our knowledge of the nutrition of most types of Protozoa has left the position substantially unaltered. A few cultures of Protozoa on defined medium in the absence of other living organisms have been established (Doyle, 1943). Notably Chilomonas (Mast, Pace & Mast, 1936; Hutchens, 1939) and Tetrahymena (Kidder & Dewey, 1945) have been grown in a culture suitable for metabolic studies; many types have not been cultured free from their living food organisms, e.g. Amoeba and Spirostomum, and the bacteria-free culture of Paramecium of Johnson & Baker (1942) has a division rate so low as to render its use in metabolic studies impracticable.