Dr Anjani Ganase discusses the use of DNA studies and technology to understand and manage our environment.
When William Blake wrote in the late 18th century, “To see a world in a grain of sand and heaven in a wildflower; hold infinity in the palm of your hand and eternity in an hour,” did he envisage that within two centuries later, scientists could explore an entire ecosystem from minute traces of matter? This is how we are learning more about the earth’s history. Will we be able to use this information to help us create a better future?
The study of ecology allows scientists to explore and immerse themselves in observing the relationships between an organism and its physical and chemical surroundings. Everything an organism does in its environment is evident in the DNA tracks left behind. DNA, or deoxyribonucleic acid, is the genetic instruction carried in the cells of all living organisms.
DNA is everywhere: in sloughed off dead cells, any drop of saliva or remnant of what was once alive.
Today, the use of hostless DNA found in the environment (environmental DNA or eDNA for short) has become useful for dramatically extending our observations to the unseen, unheard and unobserved life in the environment. Environmental DNA refers to any DNA collected in samples such as soil, sediment or water, that contains material shed by living organisms. From the samples, we can detect the presence of known species and ascertain the species diversity of multiple creatures – animals, plants, fungi, even pathogens – in a given location. Collection over time can give an indication of the degree of interaction or sharing of the same habitat and how the habitat may have changed.
How does it work?
Environmental samples, whether from soil or sediment or water samples collected from the river or the ocean, can be examined for DNA. All DNA present in the sample is extracted and then DNA of interest is amplified using a PCR (polymerase chain reaction – yes, the same used for detecting covid19). A DNA barcode is used to select a specific section of the DNA which is matched with a known reference library of species DNA.
Recreating ancient ecosystems
This was the tool used to recreate ancient ecosystems. Scientists would extract eDNA from soil samples taken from sediment cores. Within the sediment cores, scientists can observe the presence of pollen and seeds to identify the trees and plants that may have existed thousands of years ago. Now with the use of eDNA (that has not decomposed) they can identify all forms of life that have left traces.
[caption id="attachment_945083" align="alignnone" width="1024"] A man and his dog enjoy the view at Turtle Rock -[/caption]
Many studies have identified the presence of extinct mammals, birds, plants even fungi and insects. In this way, a more comprehensive picture of ancient ecosystems has emerged. For example, the eDNA method showed that there was significant overlap in time between the woolly mammoth and humans in North America and it was likely that the woolly mammoths may
