Microbiology and microbial contaminants of brewing

Abstract

The science of microbiology (micro = very small, bios = life) is con-cerned with the study of organisms less than 1 mm in size. Such organisms may be acellular (for example, viruses) or cellular. All cellular life forms are considered to have evolved from Progenotes (unknown forms) with branches leading to the Archaea (representatives of this group of microorganisms are still around today occupying places of high temperature and pressure, e.g., thermal Springs); the Eubacteria (Bacteria) and the Eukarya. The Archaea have characteristics in common with both the Bacteria and the Eukarya. All Archaea and Eubacteria are microbes. The Archaea and Eubacteria collectively are termed prokaryotes (pro- before, karyon-nucleus). All beer spoilage bacteria belong to the kingdom of the Eubacteria. Members of the Eukarya (= true nucleus) are characterized by possessing a true nucleus. The nucleus is an organelle, surrounded by a double membrane, that contains the chromosomes of the organism. The Eukarya may be subdivided into two groups, lower and higher. Lower Eukarya of interest to the brewer are the brewing yeast, wild yeasts, and other fungi (molds).