ABSTRACT
The plate count technique is one of the most routinely used procedures because of the enumeration of viable cells by this method. This method is based on the principle that when material containing bacteria is cultured, every viable bacterium develops into a visible colony on a nutrient agar medium. Bacterial population or amount of growth can be determined by measuring turbidity or optical density of a broth culture. Turbidity is quantified with the spectrophotometer that measures the amount of light transmitted or absorbed directly through a sample. It transmits a beam of light at a single wavelength through a liquid culture. The density of a cell suspension is expressed as absorbance or optical density which is directly proportional to the cells’ concentration. Microbiological analysis of plant, soil, and air samples requires quantitative determination, that is, total population of microorganisms in these substrates.
