MICROBIAL MUTATION- THE DAMOCLES SWORD OVER MANKIND

In the year 1972 I gave a radio talk on Louise Pasteur the French genius biochemist and microbiologist at the invitation of All India Radio. I concluded the talk with my quotation “It is a constant and perennial struggle between man and the microbe where each one tries to outwit the other”. This will become clearer to you as I progress with this my narration.

Sir William Osler the Canadian born doctor famous for his clinical studies, who held the position of Regious Professor of medicine at Oxford University said this

“Variability is the law of life, and as no two faces are the same, so no two bodies are alike and as no two individuals react alike and behave alike under the abnormal conditions which we know as disease”

In the drama of microbial mutation and mankind I am reminded of a biblical story of David and the giant Goliath. I depict the little boy David to microbe and the egoistic mankind to the giant Goliath. The sling used by David as a weapon I compare to the preselective mutants in the microbial population. The weapon of preselective mutation is a boon given by nature to the microbial world.

Here we have to understand the difference between preselective and selective mutation. Selective mutation comes out when a biological system is exposed to selection pressure. To illustrate it little more clearly, I am a rice eater when I am forced to eat wheat daily under coercion I get adapted to wheat, and wheat is the selection pressure and I am the selective mutant.

Microbes are smarter than man. They have the boon called preselective mutation. Even without exposing to selection pressure they spontaneously produce mutants anticipating the onslaught antimicrobial drugs in their population. Antimicrobial drugs are the section pressure.

The preselective mutants are the DAMOCLES SWORD. This will become very clear when I explain with this example.

Let us consider in a community strepto coccus sore throat appears in large number of people. The doctors apply penicillin antibiotic in the form of injection or tablet. All are cured. In that community now the preselective mutants resistant to penicillin are present but at a very very low frequency or number. So, the community is cured and saved. In the next season same, sore throat appears in a greater number of people. Physicians apply penillin and all are cured. In the bacterial population peselective penicillin resistant mutants also increase in number. A little more than the previous year. As the years go by and doctors go on prescribing penicillin drug and the number penicillin resistant mutants also increase in number. A stage will come when the bacterial population will be full of penicillin resistant preselective mutants and the doctors realize that the penicillin has become ineffective. Scientists will be on the move to discover more potent antibiotic. This will go on forever. As I mentioned earlier in my quotation, “IT IS A CONSTANT AND PERENNIAL STRUGGLE BETWEEN MAN AND MICROBE WHERE EACH ONE TRIES TO OUTWIT THE OTHER”. The existence of preselective or preadaptive mutants in microbial population was proved by Salvador Luria and Max Delbrück with their fluctuation test supported by the statistical Poisson Distribution calculation and by Joshua Lederberg with his Replica Plate Technique. Luria and Delbrück were awarded the Nobel prize for their work in 1969 and Lederberg was awarded the Nobel prize in 1958.

But the DAMOCLES SWORD of microbial mutants still hangs over the head of mankind.

THE STARTLING EXAMPLE OF TODAY IS THE VARIANTS OR MUTANTS OF CORONA VIRUS.

PROFESSOR K.A.BALASUBRAMANIAN

Ph.D. (IARI NEW DELHI), Ph.D. (LONDON), DIC(LONDON)