ABSTRACT
Many microorganisms are beneficial to mankind, and life as the people know it would not exist without their activities. Microorganisms which can cause disease are known as pathogens, and it is imperative that food is processed in such a manner that pathogens are absent from it. Although a major aim of the food industry is to eliminate unwanted microorganisms from its premises and products, there are some products which are manufactured using the beneficial activities of microorganisms! Cheese is prepared by allowing certain bacteria, known as lactic acid bacteria, to grow in milk. There are many thousands of different microorganisms, and it is important that the people group them in such a way that they can recognize their similarities and differences. Like bacteria, yeasts are single-celled microorganisms, but although they are considerably larger than bacteria. There are many types of viruses, some of which infect plants, some infect animals and others even infect microorganisms such as bacteria.
