Introduction
A group of evolutionary biologists from Indian Institute of Science Education and Research (IISER), Pune, in March 2020 came out with research findings revealing the link between the population size of bacteria and the kind of fitness trade-offs they adopt while studying culture of E.coli bacteria.
Concept of Fitness Trade-off
The concept of fitness trade-off can be understood in terms of organisms trying to adapt to different conditions or to maximise their efficiency. When organisms enhance one function, another function suffers, or when they adapt to survive well in one environment, they cannot reproduce or survive well in another environments, i.e., organisms do not have the capacity to maximise all their functions at the same time. So, species prefer one environment to another, called fitness trade-off.
Findings of the Study
In the course of evolution, some organisms develop into generalists and others into specialists. Generalists can survive in different environments, basically with a tolerable level of fitness in all environments. Specialists, on the other hand, have a high degree of fitness in a particular environment with low fitness in other environments. The study shows that large populations have a tendency to evolve into specialists and small ones evolve into generalists. So, there is a link between population size and evolution of fitness trade-off. Larger populations become more vulnerable to sudden changes in the environment due to their higher extent of specialisation.
If the environment abruptly shifts between two states that show fitness trade-off with each other, then populations with a history of evolution at higher numbers would be at a greater disadvantage than historically smaller populations.
An example of this is antibiotic resistance; generalists are equipped to tolerate a wide variety of antibiotics owing to their ability to adopt to diverse condition, whereas, specialists bacteria have to show a fitness trade-off in this regard. They can resist one antibiotic but can become susceptible to another one. Similarly, pathogens are also expected to experience fitness trade-off when they migrate across different hosts.
The results of the study are important in understanding the population genetics of ecological specialisation and vulnerability to environmental changes. The paper, co-authored by Prof. Sutirth Dey and his collaborator, Yashraj Chavhan, was published in the journal Heredity.
About E.coli
Escherichia coli, also known as E.coli is a Gram-negative, facultative anacrobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms, environment, foods, etc. E.coli are a large and diverse group of bacteria. Though harmless in general, others can make you sick. Some of them can cause diarrhea, while others can cause urinary tract infections, respiratory illness, and pneumonia, etc.
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