Environmental DNA or eDNA is DNA that is collected from a
variety of environmental samples such as soil, seawater, snow or air,
rather than directly sampled from an individual organism. As various
organisms interact with the environment, DNA is expelled and
accumulates in their surroundings from various sources. Such eDNA
can be sequenced by environmental omics to reveal facts about the
species that are present in an ecosystem
Environmental DNA sampling allows for precise, DNA marker-based
taxonomic identification, including
taxa that are small, cryptic, and/or difficult to distinguish
morphologically. In comparison with traditional
collection and identification methods, such as electrofishing, seine or
trawl nets, trapping, or visual surveys, eDNA techniques and sampling
strategies may be highly targeted and sensitive for rare species or
those that are at low densities in the sampling area.
The steps involved in eDNA analysis include-
- Sample collection- Samples are collected from water, soil,
sediment and air. - Concentration- The target DNA in the environment is in very
small quantities thus a wide net is casted and concentration
methods like filtration , alcohol precipitation , etc are used to
collect a-lot of DNA in small volume - DNA extraction- This process purifies the DNA from everything
else in the sample.It is done with commercially available DNA
extraction kits - Amplification- A genetic marker needs to be amplified by qPCR
(quantitative polymerase chain reaction) to create a high quantity
of DNA copies. DNA primers are matched with the DNA sequence
and if the primers match, the chemical reaction will make numerous
copies of that DNA. - Quantitative PCR detection- a target sequence is detected with
fluorescent signal amplification.
APPLICATIONS OF eDNA
To monitor biodiversityEnvironmental DNA (eDNA) is a revolutionary method to the study of
biodiversity of any environment.
Environmental DNA meta barcoding is a non-invasive method for
discovering and identifying rare and endangered species in a variety of
ecosystems, including aquatic environments, based on the retrieval of
genetic traces emitted into the environment .
Meta barcoding is the barcoding of DNA/RNA(or eDNA/eRNA) in a
manner that allows for the simultaneous identification of many taxa
within the same sample.It can be precisely defined as the use of
general or universal polymerase chain reaction (PCR) primers on
mixed DNA samples from any origin followed by high-throughout
next generation sequencing (NGS) to determine the species
composition of the sample.
Every organism has a unique DNA barcode, which is a variable
region between conserved genomic regions. eDNA meta barcoding
amplifies and sequences these barcodes. Environmental DNA (eDNA)
provides a novel source material for researchers and conservationists
to monitor biodiversity and record alien & invasive species from the
water and organic sediments that they leave behind in the environment
To detect rare or invasive speciesThere are significant threats to aquatic ecosystems from the
introduction and spread of aquatic invasive species (AIS), hence it is
crucial to detect these invaders as early as possible.Aquatic,
introduced species have devastating effects on native biodiversity
because they may eat native species, compete with them, degrade
habitats, or spread diseases.
eDNA sample coupled with qPCR analysis which is a molecular
technique that measures the amount of a DNA sequence in a
sample,has become an effective technique, notably for AIS
identification, among the instruments available for underwater species
tracking.
Therefore, managers can take rapid action to detect the spread and
settlement of invasive species in aquatic environments by confirming
their presence using eDNA in a period of hours or days rather than
weeks or months.
CONCLUSION
In conclusion, the use of technologies based on eDNA has the
potential to significantly increase our capability for the scientific
study and protection of biodiversity and conservation.
Using eDNA for monitoring biodiversity may provide a simple,
cheap, and standardized technique to collect crucial information on
the subterranean and aquatic invasive species range and population
size, allowing for more effective use of minimal conservation funds
and taxonomic knowledge.
It’s non invasive and cost effective method of identifying species in
their natural habitat makes it highly accessible to researchers ,
conservationists, and citizen scientists.
Author – Ganya Sethi
St. Joseph’s Academy
