Antibiotic Resistance

June 28, 2021

Syllabus- General Studies 3(science and technology)

Context

During evolution, the fitness costs experienced by bacteria under constant and fluctuating environments pose a problem that has not be solved. One way of seeing this is through the example of multi-drug resistance. It is not clear why some bacteria evolve multi-drug resistance while others do not. New research from the Population Biology Lab at IISER Pune could hold a key to this and a similar class of puzzles.

Multi-drug resistance:

It is a menace in public health, however, it is a fascinating problem to an evolutionary biologist who sees it from this angle:

Possessing multi-drug resistance implies that the bacteria is adept at handling multiple antibiotics simultaneously.

This would increase its fitness appreciably.
Given that antibiotics exert a very strong selection pressure, it would appear that every bacteria in nature can become multi-drug resistant, which is not the case.

Key Highlights of the Study:

The scientist group studied approximately 480 generations of E. coli in four types of steady environments consisting of different carbon sources:

Galactose,
Thymidine,
Maltose and

They also perform a study in one fluctuating environment in which the carbon source changed unpredictably between these four.
It was found that bacteria cannot use all carbon sources similarly.

Which carbon source is available impacts the bacterium’s ability to survive and grow.

It was found that small populations acquire a certain set of mutations that allow them to survive in one environment while paying a cost in others.
Large populations also develop these mutations but, in addition, have certain compensatory mutations that together give them fitness to survive in different environments.

Thus, population size determines the kind of mutations available to the bacteria, which in turn, leads to the type of fitness costs they evolve.
Thelarger populations contained a greater number of mutations.
Thesmaller populations only had mutations related to the metabolism of one kind of carbon source whereas the larger populations had known mutations for the metabolism of multiple types of carbon sources.

So the study concluded that when the environment is fluctuating, large (but not small) populations can by-pass this effect.

Question- Write a short note on Antibiotic Resistance and its impact.

Article- https://www.thehindu.com/sci-tech/science/why-only-some-bacteria-develop-multi-drug-resistance/article34993440.ece