Lysozyme
Alexander Fleming's discovery of its anti-bacterial properties
How Dr Alexander Fleming, in 1922, discovered the anti-bacterial properties of lysozyme, first in his own nasal mucus and subsequently in tears
St Mary’s
In 1906 Dr Alexander Fleming (1881–1955) joined the Inoculation Department of the old Medical School at St Mary’s Hospital, London. His range of research interests in those early years are reflected in the wide range of publications that he authored. For example, in 1909 he wrote ‘On the etiology of acne vulgaris and its treatment by vaccines’, which appeared in the Lancet (vol. 1, p. 1035), and in the same year, the same journal published ‘A simple method of serum diagnosis of syphilis’ (vol. 1, p. 1512). His military service during the Great War prompted a series of articles on the bacteriology of wound infections, and his growing interest in antiseptics was reflected in a 1917 article for the Lancet (vol. 2, p. 341) entitled ‘The physiological and antiseptic action of flavine, with some observations on the testing of antiseptics.’
A Fortuitous Cold
In 1922, while clearing away some old Petri dishes which had been lying on his bench for up to a fortnight, he paused to look at one dish in particular, before remarking to his colleague, Dr Allison, ‘This is interesting.’ The dish was covered with large yellow colonies … except for a wide area where there were no organisms visible. Fleming explained that while suffering from a cold, he had added some of his own nasal mucus to the same area of the plate were no organisms were growing. It occurred to him that there was something in the mucus that had not only killed the microbes in the immediate vicinity, but which had also diffused outward to weaken already developed colonies.
Tears
Having confirmed this observation by experiment, he next tried the effect of tears. When he added a single drop of tear fluid to a broth culture of microbes the organisms dissolved in a matter of seconds. As Dr Allison commented, ‘For the next five weeks, my tears and his were the main supply of material for experiment.’ To stimulate tear production they would squeeze a small piece of lemon peel into their eyes and aspirate the fluid with a Pasteur pipette. Even the laboratory assistants were recruited to the ‘ordeal by lemon’, for which they were paid threepence a time.
Lysozyme
Fleming then demonstrated that the substance had the properties of an enzyme. But what should it be called? Fleming’s boss, Sir Almroth Wright, who had a passion for Greek, decreed that as it was an enzyme, it must end in –zyme, and because it dissolved , or lysed, certain microbes, it was agreed to give it the name, lysozyme. As for the microbe that it had destroyed, Wright called it micrococcus lysodeikticus, from ‘lysis’ for dissolution, and ‘deixein’ to show. In other words, the organism that makes it possible to show an ability to dissolve. Fleming’s initial observations were published in a 1922 article which appeared in the Proceedings of the Royal Society, and entitled ‘On a remarkable bacteriolytic element found in tissues and secretions.’ Six years later he discovered an even more remarkable bacteriolytic element: penicillin.
