Interrelationships between a Yeast and a Bacterium when growing together in Defined Medium

Abstract

SINCE the introduction of solid medium, the isolation of micro-organisms in pure culture, formerly a matter of considerable difficulty, has become a relatively easy process. The numerous studies of micro-organisms in pure culture which resulted have enabled the science of microbiology to develop rapidly. In Nature, however, micro-organisms are rarely found in pure culture, and there is a need for investigation of the growth and metabolism of organisms growing in association with each other. Woods¹ has recently stressed the need for such research. The present study of a yeast (Saccharomyces cerevisiae) and of a bacterium (a Lactobacillus species) growing separately, and also when growing in association with each other in defined media, was commenced approximately two and a half years ago and is concerned mainly with the nutritional requirements of the micro-organisms. A number of interesting relationships between the organisms when in mixed culture have been observed.