This word was known long ago to physicians and microbiologists, and was mentioned in special books But until fairly recently it meant absolutely nothing to anyone not connected with biology or medicine. Nor did many chemists know its meaning. Now everybody knows it. The word is �antibiotics.�

But before the layman came to know the word �antibiotics,� he learnt the word �microbes.� It was established that a number of diseases such as pneumonia, meningitis, dysentery, typhus, tuberculosis and others, are due to microorganisms Antibiotics were needed to fight these microorganisms.

The curative action of some kind of moulds was known as far back as the Middle Ages. True, the ideas of the medieval Aesculapii were rather peculiar. For instance, it was thought that the only kind of mould that helped in curing diseases was that taken from the sculls of men hanged or executed for a crime.

But this is of no great significance. What does matter is that the British chemist Alexander Fleming was successful in isolating the active principle from a species of fungus mould he was studying. This resulted in penicillin, the first antibiotic.

Penicillin proved to be an excellent weapon in the fight against pathological microorganisms: streptococci, staphylococci, etc. It even vanquishes the Spirochaeta pallida, the microbe that causes syphilis.

But though Alexander Fleming discovered penicillin in 1928 its formula was established only in 1945. By 1947 penicillin had been fully synthesized in the laboratory. It seemed that man had finally caught up with nature. But this was not quite so. The laboratory synthesis of penicillin is no simple thing; it is much easier to produce it from mould.

But the chemists were not to be daunted. Here too they had their say and were able to put out a good showing. The �productivity� of the mould penicillin was usually prepared from was very low, and the scientists decided to raise its efficiency.

They found substances which, inculcated into the hereditary apparatus of the microorganism, altered its characters. Moreover, these new characters became hereditary. The result was a new strain of fungi, which produced penicillin much more actively.

The present-day assortment of antibiotics is quite impressive; streptomycin and terramycin, tetracycline and aureomycin, biomycin and erythromycin. Altogether about one thousand different antibiotics are known today and around one hundred of them are used for treating different maladies. Chemistry plays a major part in their preparation.

After the microbiologists have accumulated what is known as the liquid culture medium containing colonies of microorganisms, the chemists take over.

It is their task to isolate the antibiotics, the �active principle.� Various chemical methods are employed for extracting complex organic compounds from natural �raw materials.� The antibiotics are taken up by special absorbents. Investigators use �chemical pincers,� i.e., extract the antibiotics by means of various solvents. They purify them with ion-exchange resins, and precipitate them from solutions. This results in a raw antibiotic which is then subjected to a lengthy cycle of refining operations until it finally becomes a pure crystalline substance.

Some of them, such as penicillin, are still synthesized with the aid of microorganisms. But the production of others is only half due to nature.

But there are antibiotics, such as synthomycin, which chemists produce without the aid of nature at all. Such preparations are synthesized from beginning to end at chemical plants.

Without the powerful methods of chemistry the word �antibiotic� could never have become so widely known, nor would the veritable revolution in medicine, caused by these antibiotics, ever have happened.

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