Practice 11 - Counting of halophilic, osmophilic, and xerophilic microorganisms

Abstract

Extreme environments provide habitats for some groups of microorganisms, for example, foods preserved by dehydration, enhancing amounts of sugars, and increasing hypersaline environments. The microbes surviving in low water activity (dehydrated) foods are dominated by xerophilic molds (dry-loving). The microbes surviving in high-sugar foods are dominated by osmophilic yeasts. The microbes surviving in high-salt foods or a high-salt environment are dominated by halophilic bacteria, yeasts, and molds. The pour plate technique is used in the counting of osmophilic microorganisms from food products. Different media can be used in the counting of osmophilic microorganisms. Halophilic microorganisms are counted by plate count techniques using media containing 3% NaCl. Xerophilic microorganisms can be counted by plate count techniques using media containing higher amount of sugar (e.g., glucose or sucrose).