History and Microscopy Methods

Pioneers of microbiology

Microbiology is built on the work of a few pioneers, and each is remembered for one specific contribution, so the key is to link each name with its field. Elie Metchnikoff, a zoologist, first described phagocytosis, the engulfment of foreign particles by amoeboid cells, and proposed that these cells provide host defence, which established cellular immunology. Robert Hooke is associated with early microscopy and the term cell, whereas Robert Koch is known for the germ theory of disease and Koch's postulates. Chemotherapy, in the modern sense of using a chemical agent that selectively destroys a pathogen, was pioneered by Paul Ehrlich, who proposed the 'magic bullet' concept and the principle of selective toxicity. In 1909 he introduced Salvarsan (arsphenamine), the first effective chemical treatment for syphilis. Ronald Ross is a major figure in parasitology, having demonstrated mosquito transmission of malaria, but he is not the pioneer of chemotherapy. Robert Koch developed solid media and nutrient broth prepared from meat infusion so that pure cultures of bacteria could be obtained. Because these media supported the growth of pathogenic organisms, Koch could isolate and identify the causative agents of diseases such as anthrax and tuberculosis. The meat-based medium therefore served to cultivate disease-causing microbes, whereas air sampling, sterility testing and screening of antimicrobial activity are handled by other methods. The doctrine of spontaneous generation, the belief that living organisms arise from non-living matter, was refuted by several scientists. Louis Pasteur's swan-neck flask experiments showed that sterile broth stays free of microbes when airborne contamination is excluded. John Tyndall showed that dust carries microbes and used fractional sterilisation to demonstrate that heat-resistant forms survive boiling. Ferdinand Cohn described heat-resistant bacterial endospores of the genus Bacillus, which explained how microbial growth could persist after boiling. John Needham, in contrast, defended spontaneous generation and therefore did not contribute to its refutation.