The Australian Science Education Project is producing materials designed for use in grades 7-10 of Australian schools. This is the first trial version of a unit investigating microbial action. One of the student booklets contains instructions for the activities demonstrating food decay which all students are expected to complete. The other student booklet, accompanied by worksheets, contains suggestions for ten optional activities concerned with the effects of bacteria and fungi, their uses in food processing and role in ecological cycles, and an historical study of Pasteur's work. Objectives for the unit, suggestions for instructional organization, reference and materials lists for each activity, and methods of organizing discussion are included in the separate teacher's guide. A test booklet and a sheet of answers, including diagnostic comments, are available. (AL)