History of Microbiology

History of Microbiology Man kind has always been affected by diseases which were originally believed to be visitations by the gods and meant to punish evil doers. Hippocratus, father of medicine, observed that ill health resulted due to changes in air, winds, water, climate, food, nature of soil and habits of people. Varro (117-26 BC)said a theory that disease was caused by animated particles invisible to naked eye but which were carried in the air through the mouth and nose into the body. Fracastorius (1500 G.C.) proposed that the agents of communicable disease were living germs, that could be transmitted by direct contact with humans and animals, and indirectly by objects ; but no proof because of lacking experimental evidence. Antony Van Leeuwenhoek ( G.C.), father of Microbiology, observed “animalcules” using simple microscope with one lens. He was the first who properly described the different shapes of bacteria. Although Leeuwenhoek was not concerned about the origin of micro-organism; many other scientists were searching for an explanation for spontaneous appearance of living things from decaying meat, stagnating ponds, fermenting grains and infected wounds. On the bases of this observation, two major theories were formulated. 1. 2. Theory of Abiogenesis Theory of Biogenesis 2 Medical Bacteriology Theory of Abiogenesis deals with the theory of spontaneous generation; stating that living things originated from non-living things. Aristotle (384-322 BC): The founder of a theory spontaneous generation. He observed spontaneous existence of fishes from dried ponds, when the pond was filled with rain. Francesco Redi (): He is the scientist who first tried to set an experiment to disprove spontaneous generation. - He put the meat in a bottle and covered it with a gauze. - - He observed that the flies laid eggs from which the maggots developed. He said maggots did not developed from meat but from flies egg. Theory of Biogenesis states that life comes from pre-existing life. Louis Pasteur ( GC) was the scientist who disproved the theory of abiogenesis. He designed a large curved flask (Pasteur goose neck flask) and placed a sterile growth broth medium. Air freely moved through the tube; but dust particles were trapped in the curved portion of flask. Microbial growth in the broth was not seen. Therefore Pasteur proved that micro-organisms entered to substrates through the air and micro-organisms did not evolve spontaneously. Major contribution of Louis Pasteur 1. 2. Microbial theory of fermentation Principles and practice of sterilization and pasteurization 3 Medical Bacteriology 3. 4. 5. Control of diseases of silk worms Development of vaccines against anthrax and rabies. Discovery of streptococci The germ theory of disease The complete establishment of the germ theory of disease depended on the work of a German scientist, Robert Koch (1843 1910). Major achievements of Robert Koch 1. 2. Discovery and use of solid medium in bacteriology Discovery of causative agents of tuberculosis and cholera. 3. Koch’s phenomenon 4. Koch’s postulates Koch’s postulates: proof of germ theory of disease 2. A micro-organism can be accepted as a causative agent of an infectious disease only if the following conditions are satisfied. 1. The micro-organism should be found in every case of the disease and under conditions which explain the pathological changes and clinical features. It should be possible to isolate the causative agent in pure culture from the lesion. 3. 4. 5. When such pure culture is inoculated into appropriate laboratory animal, the lesion of the disease should be reproduced. It should be possible to reisolate the bacterium in pure culture from the lesion produced in the experimental animal. Now a days additional postulate is mentioned i.e.