Scientists find evidence of virus-eating microorganisms
New York: Scientists have found the first compelling evidence that two groups of ecologically important marine microorganisms could be eating viruses -- catching their "prey" and engulfing them, an advance that may lead to a better understanding of the flow of organic matter in the oceans.
The findings, published in the journal Frontiers in Microbiology, go against the currently predominant views of the role of both viruses and these groups of single-celled organisms called protists in the marine food webs.
"Our data show that many protist cells contain DNA of a wide variety of non-infectious viruses but not bacteria, strong evidence that they are feeding on viruses rather than on bacteria," said study corresponding author Ramunas Stepanauskas, Director of the Single Cell Genomics Center at Bigelow Laboratory for Ocean Sciences in the US.
The scientists explained that the predominant model of the role of viruses in the marine ecosystem is that of the "viral shunt," where microbes infected with viruses lose a substantial fraction of their chemicals back to the pool of dissolved organic matter.
However, the current study noted that the viral shunt could be complemented by a link in the marine microbial food web which may constitute a "sink of viral particles in the ocean."
According to the researchers, this finding "has implications for the flow of carbon through the microbial food web."
In the study, Stepanauskas and his colleagues sampled surface seawater from the Northwestern Atlantic in the Gulf of Maine in the US in July 2009, and the Mediterranean off Catalonia, Spain in January and July 2016.
They used modern single-cell genomics tools to sequence the total DNA from 1,698 individual protists in the water, and found evidence of protists with or without associated DNA.
The researchers explained that the associated DNA could be from symbiotic organisms, ingested prey, or viruses or bacteria sticking to the protists' exterior.
While the technique is very sensitive, the scientists said it doesn't directly show the type of relationship between a protist and its associates.
The scientists found a range of protists including groups called alveolates, stramenopiles, chlorophytes, cercozoans, picozoans, and choanozoans.
They said 19 per cent of the genome from the single cell organisms taken from the Gulf of Maine and 48 per cent of those from the Mediterranean were associated with bacterial DNA, suggesting that these protists had eaten bacteria.
But they added that viral sequences were more common, making up 51 per cent of the protists' genome from the Gulf of Maine and 35 per cent of those from the Mediterranean, with a frequency of one to 52 virus types per protist.
According to the researchers, most of these were from viruses known to infect bacteria -- presumably representing parasites of the protists' bacterial prey.
But they said choanozoans and picozoans, which only occurred in the Gulf of Maine sample, were different since these groups, neither of which have chloroplasts, are poorly known.
The scientists noted that the choanozoans are of great evolutionary interest as the closest living relatives of animals and fungi.
The tiny single-celled organisms were first discovered twenty years ago, and until now, their food sources were a puzzle, as their feeding apparatus is too small for bacteria, but ample for viruses, the researchers said.
In the current research, they found that every single one of the choanozoan and picozoan genomes were associated with viral sequences from bacteria-eating viruses called phages, but mostly without any bacterial DNA.
The same genome sequences were found across a great diversity of species, the study noted.
"It is very unlikely that these viruses are capable of infecting all the protists in which they were found," said Julia Brown, a co-author of the study at the Bigelow Laboratory for Ocean Sciences.
Based on these findings, the scientists concluded that choanozoans and picozoans "probably routinely eat viruses."
"Viruses are rich in phosphorus and nitrogen, and could potentially be a good supplement to a carbon-rich diet that might include cellular prey or carbon-rich marine colloids," Brown said.
The scientists believe the removal of viruses from the water may reduce the number of viruses available to infect other organisms, while also shuttling the organic carbon within virus particles higher up the food chain.
"Future research might consider whether protists that consume viruses accumulate DNA sequences from their viral prey within their own genomes, or consider how they might protect themselves from infection," Brown said.
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Inappropriate for MLAs seeking free IPL tickets, says D.K. Suresh
Bengaluru: Bengaluru Milk Union Ltd President D.K. Suresh on Monday said it is inappropriate for MLAs to seek free IPL tickets, adding that those interested in watching matches should pay for them personally.
Speaking to reporters near his residence in Sadashivanagar, he said, “IPL is a commercial tournament and does not represent the country. It is not right for public representatives to focus too much on such matters.”
Referring to the recent controversy during the RCB celebrations, he said, “let us find out who benefited the most from the statements made during the incident.” He also pointed out that BJP MLAs had received IPL tickets as well.
Responding to discussions about relocating the Chinnaswamy Stadium, Suresh said the government has already approved the construction of a new stadium at a location he had proposed.
“I had suggested building a stadium in Surya City and submitted a proposal for it. Bengaluru needs four stadiums in four directions to cater to its growing population and encourage youth participation in sports,” he said.
He noted that apart from Kanteerava Stadium, KSCA, and the Football Stadium, there are limited facilities in the city.
“When I was a Lok Sabha member, I had proposed allocating 100 acres in my constituency at Surya City. The land was later earmarked and the plan approved,” he added.
Suresh said he has discussed the project with Minister Zameer Ahmed Khan, Rajiv Gandhi Housing Corporation Chairman Shivalingegowda, and Anekal MLA Shivanna.
“The Cabinet has now approved the project, and a stadium will be developed on around 50–60 acres,” he said.
He further added that he has requested the Deputy Chief Minister to build another stadium at Shivarama Karanth Layout through the BDA, where 40 acres have been allocated. Plans are also being discussed to develop a well-equipped stadium in Bidadi.
Commending state government's recent bilingual policy move, Suresh said forcing children to learn three languages could affect their comprehension.
“It is a good decision to make two languages compulsory. Learning a third language should be left to the choice of students and parents,” he said.
Responding to criticism from BJP leaders, he said their tendency is to oppose every decision of the government.
“To please their central leadership, they take a pro-Hindi stance. Instead, they should advocate for the adoption of Kannada in all states,” he said.
When asked about the earlier three-language policy under Congress, he said, “the situation is different now. Today, the focus should be on quality learning. Kannada should remain the primary language, while students and parents can choose an additional language.”
