Genetics | Evolution | Natural Selection in Nature | Antibiotic Resistance | Mycobacterium tuberculosis | rpoB gene

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Antibiotic Resistance in Mycobacterium tuberculosis

In 1980s, bacteria causing tuberculosis (Mycobacterium tuberculosis) was treated with antibiotic rifampin. But in 1993, a new strain of M. tuberculosis was found, that was resistant to rifampin and other antibiotics and TB became a global threat. Scientists found that the genome of resistant strain of M. tuberculosis developed a point mutation in gene rpoB, where a cytosine was replaced by thymine and the normal codon TCG mutated to TTG . The polymerase produced by mutated gene had leucine instead of serine at l53rd amino acid in the polypeptide chain. The drug rifampin was unable to bind to mutant RNA polymerase and M. tuberculosis became resistant to the drug.

Such antibiotic-resistant bacteria survived and multiplied to produce more and more bacteria of resistant strain. The normal bacteria non-resistant to antibiotics died off.

Resistance to a wide variety of insecticides, fungicides, antibiotics, antiviral drugs and herbicides has evolved in some insects, fungi, bacteria, viruses and plants, and such resistant varieties have been favoured by natural selection.


source: Organic Evolution (Evolutionary Biology), 13th edition, Medtech, by Veer Bala Rastogi , pg 304


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