Context: Bats can host a wide variety of pathogens, including ones deadly to other mammals, but they themselves do not get infected. Scientists have been curious about the source of this protection.
Facts about Bats
- Bats are the only mammals on the earth that can maintain sustained flight.
- They have relatively long life spans and are relatively more protected from a variety of diseases, including cancer.
- They have a unique ability in echolocation, whereby they use sound to navigate and locate objects. This frees them from being constrained by the availability of light, unlike humans.
- By population, bats make up 20% of all mammals. There are more than 1400 species of bats around the world.
- The bumblebee bat weighs only 2 grams.
- Flying foxes (bats) have a wingspan of 1.5 metres and weigh up to 1.6 kg.
- Bats play crucial roles in maintaining the ecological balance and are essential for pollination, insect control, etc.
Bats as reservoirs of pathogens
- Bats can act as a reservoir/host for many viruses including coronaviruses, Nipah, Ebola, Marburg virus, and Hendra virus etc.
- Despite hosting a wide variety of pathogens, even multiple viruses at the same time, which are deadly to other mammals, bats do not get infected.
- Genome sequencing has become the mainstay of investigations of the viruses that bats carry, also known as the bat virome.
- Bat1K global genome consortium which aims to sequence all the 1400 or so bat species’ genomes is currently underway.
- Over the years, researchers have unearthed significant insights by sequencing the genomes of many bat species. (Bats have a relatively small genome with around 2 billion bases).
- On comparing the genomes of a fruit-eating and an insect-eating species, scientists found that genes involved in metabolism and immune response have been positively selected. This means that these bats have evolved by improving these two biological domains.
- Natural selection of a protein called prestin is involved in echolocation (dolphins have the same protein).
- The subsets of genes involved in mounting an immune response – which encode proteins called interferons (IFN) – had contracted significantly in bats. This allowed bats to diminish the pro-inflammatory response against a number of viruses, thus protecting themselves from clinical disease.
- A number of genes involved in suppressing tumours and in repairing DNA contained signs of positive selection. This could contribute to the bats’ longer life span and a significantly lower risk of developing cancer.
- Natural selection is defined as a process in nature through which living organisms adapt and change in response to an environmental condition (climate, temperature, availability of resources, etc.)
- There are two types of natural selection in biological evolution: Positive (Darwinian) selection promotes the spread of beneficial alleles, and negative (or purifying) selection hinders the spread of harmful alleles.
With rapid deforestation, ecological degradation, and increased human-animal interactions, the risk of outbreaks of zoonotic diseases has heightened. (E.g., Nipah outbreaks in Kerala, Marburg disease and Ebola virus in some African countries). Hence, genome sequencing can help humans in understanding the nature of the outbreaks, and deal with them effectively.