A collection of readily reproducible techniques for determining most of the important factors governing microorganisms and their habitats. Presented in step-by-step detail, these cutting-edge methods range from those for the study of marine organisms, to those for investigating microorganisms occurring in groundwater, to the biodiversity of yeasts found in remote environments. The novel protocols for studying fermented milks are significant for investigators concerned with milk as an item of food for infants, small children, and even adults. Additional methods for the recovery and determination of nucleic acids and other compounds affecting, and affected by, microorganisms are given for certain enzymes produced by plant pathogens and for obtaining microbial species tolerant of such inhibitors as heavy metals.