Tetrahymena pyriformis from Several Pacific Islands and Australia *

Abstract

From a total of 223 diverse habitats located in Australia, New Zealand, Fiji, Hawaii, Japan, Hong Kong, and the Philippines, 144 yielded Tetrahymena pyriformis. These collections were taken from a latitude of 35° N. to 35° S., from sea level to 4500 feet, and temperatures ranging from 15° to 30°C. From these habitats 2300 clones were isolated, of which approximately 800 were examined for micronuclei and 450 tested for mating type. Two distinct interbreeding populations were isolated from the Australian collections. They failed to mate with any of the 10 known varieties and are therefore designated as varieties 11 and 12. No sexually active clones were found in New Zealand, Japan or Hong Kong. However, clones belonging to variety 9, previously found only in Colombia and Panama, were isolated from habitats in Hawaii and Fiji. This evidence suggests that possibly variety 9 is confined primarily to the tropics. There seems to be no other correlation of varieties with land mass. Representative clones from each habitat were established in axenic culture, all of which grew well in proteose-peptone. When first tested, a number of mutants were found among the 66 clones screened for their nutritional requirements. Some grew without thioctic acid or niacin. Several required aspaitic acid and one required biotin and proline in addition to the 18 nutrilites required for strain E. No pattern could be found which related the mutants to a particular region. Examination of the mutants one year later revealed that the synthetic capacity for both niacin and thioctic acid had been lost and that those clones requiring aspartic acid had acquired the capacity to make the amino acid.