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Scientists discover hundreds of mysterious giant VIRUSES lurking in the ocean
It's an idea that sounds straight from the latest science fiction blockbuster.
But scientists at the University of Miami have warned that the world's oceans are teeming with 'giant viruses', also known as giruses.
Most viruses are less than 0.5 per cent the width of a human hair – too small to be seen with the naked human eye.
In contrast, the researchers say that the giant viruses are five times bigger, rivaling bacteria in terms of size.
Concerningly, all 230 giant viruses are previously unknown to science.
What's more, their impact on humans remains unclear.
Generally, giant viruses attack tiny organisms such as algae and amoebas in the world's waterways, although they could live on land too.
'The impact of giant viruses is no doubt present across all environments, but special interest has been taken to uncover their impact on aquatic ecosystems,' the experts say.
Most viruses are in the range of 20 to 200 nanometres, but giant viruses can be more than 1,000 nanometres.
For comparison, the width of a human hair is approximately 80,000 to 100,000 nanometres.
Giant viruses were practically unknown to science until the early 21st century, but scientists think they can have a major impact on life on Earth.
In the oceans, they infect various species of single-celled algae – the photosynthetic organisms that are responsible for about half of the Earth's oxygen production.
This viral infection can cause a rapid collapse of algal blooms – accumulations of algae stretching across tens of thousands of kilometers in the ocean – which in turn can substantially affect extensive marine, atmospheric and terrestrial ecosystems.
Although algae blooms can overgrow and become a problem, infection by giant viruses can have the opposite problem – causing their rapid collapse, which can deplete oxygen in the atmosphere.
Where and what types of these giant viruses exist around the world is still understudied, the researchers point out.
To learn more, they used a computer software tool called BEREN to identify the genomes of microbes in seawater samples.
What's the biggest virus?
The largest known virus, called Pithovirus, is 1,500 nanometres in length - so just over one thousandth of a millimetre.
Although Pithovirus is still invisible to the naked eye, most viruses are in the range of 20 to 200 nanometres.
For comparison, the width of a human hair is approximately 80,000 to 100,000 nanometres.
Discovered over a decade ago in the Siberian Permafrost, Pithovirus is thought to have been there 300,000 years and still able to infect living things.
The majority of giant viruses found belonged to either the Algavirales (135) or Imitervirales (81) classification.
Algavirales, typically 100 to 200 nanometres in diameter, get their name because of their ability to specifically infect the photosynthetic, single-celled eukaryotes known as algae.
Meanwhile, the 'genetically complex' Imitervirales have a flexible genetic strategy that potentially allows the virus to survive in a wider variety of hosts.
Because giant viruses contain enormous quantities of genetic material – up to 100 times more than other viruses – some may be able to better manipulate their host during infection.
This is one reason why giant viruses are thought to be more problematic than normal-sized viruses, although the factors that influence one virus being more deadly than another are varied and complex.
'Giant viruses possess genes involved in cellular functions such as carbon metabolism and photosynthesis, traditionally found only in cellular organisms,' said study author Benjamin Minch at the University of Miami.
'This suggests that giant viruses play an outsized role in manipulating their host's metabolism during infection and influencing marine biogeochemistry.'
Another giant virus classification called Pimascovirales includes the largest known virus, Pithovirus, which is 1,500 nanometres in length.
Discovered over a decade ago in the Siberian Permafrost, Pithovirus is thought to have been there 300,000 years ago and be still able to infect living things.
Most of the giant viruses (108) were from the Baltic Sea, a large brackish water body between the Scandinavian Peninsula and the rest of continental Europe, followed by the Antarctic (65).
But others were found in the Arctic, South Pacific, North Atlantic, Sargasso Sea (a specific area of the North Atlantic) and Korea's Jangmok Bay.
Overall, this suggests colder marine environments are richer reservoirs of giant viruses, many of which are likely yet to be discovered.
Cold-adapted marine giant viruses may now be threatened by climate change, further complicating the picture.
The new study, published in the journal Nature npj Viruses, offers further insight into these understudied microorganisms.
Further research could look at where giant viruses exist on land, or whether they're restricted to remote, underpopulated environments.
'This study allowed us to create a framework to improve existing tools for detecting novel viruses that could aid in our ability to monitor pollution and pathogens in our waterways,' Minch added.
WHAT IS THE DIFFERENCE BETWEEN A BACTERIA AND A VIRUS?
Viral infections, including common colds, are not treated by antibiotics, but bacterial infections, such as strep throat, can require the medications (file photo)
The biggest difference between viral and bacterial infections is the way in which they are treated.
Bacterial infections can usually be killed by antibiotics whereas the medicines to do work against viral infections.
Additionally, viruses are smaller than bacteria.
In order for a virus to multiply it must be attached to a living host, such as a human.
Bacteria thrive in a variety of environments both hot and cold.
Most bacteria are harmless, but ailments such as urinary tract infections and strep throat are caused by bacteria.
