ABSTRACT
This chapter concerns the different methods that are required for determining, for the two types of micro-organism, the amount of growth that might have occurred. Additionally, one may wish to know how many of the cells or how much of a mycelium is metabolically active or capable of continued growth. Growth of a suspension of cells can be determined as an increase in mass or cell number. Even though individual cells may be identical genetically, they differ one from another in terms of their age, dimensions, antibiotic resistance and wall composition. The wet or dry mass of a culture of cells is determined by the difference between a centrifuge tube containing the cells and the tube preweighed prior to harvesting. Collection of cells by filtration under gravity or vacuum is the customary method for determining their mass free of interstitial liquid. Direct counting is performed with a hemocytometer, which was originally designed for counting red blood cells.
