Every day scientists find bizarre, new viruses from around the world. This week, a group of researchers announced the discovery of relatively massive bacteriophages, which are bacteria-infecting viruses. The giant microorganisms dwarf not only normal-sized viruses, but also have the capacity to perform complex tricks that we also see in modern medicine.
Viruses with bigger genes than bacteria
Recently scientists have come to know an extensive catolog of viruses that seem to become unusually large, bigger even than some forms of bacteria. And their mammoth dimensions are echoed by their gargantuan genetics.
For example, the influenza A virus has eight genes, which tallies up to 13 base pairs of DNA. But with this discovery, scientists have now found genes for viruses with hundreds of genes, and more than one million base pairs.
In other words, they're visible under the weakest microscopes.
Known simply as "giant viruses," these big micro-organisms are largely found in amoebas, often in places where humans don't go. But now researchers have found that similarly-large viruses exist in places that are both more "out-there," and familiar. In 2019 a team documented giant viruses living inside the guts of people in Bangladesh. In a new study, published today in Nature, the very same team has put forward evidence of even larger viruses spread around the world.
Making the DNA Soup
Scientists study and discover new bizarre viruses by analyzing DNA collected in a soup of samples acquired from the natural world. This time, they looked at samples taken from human and animal feces, fresh and marine bodies of water, slippery mud sediments, hot springs, and elsewhere. The scientists then screened for microbes that are not the phages they're looking for. Eventually, they reconstructed genomes left in the mix.
"The genomes [we found] are large, some very much larger than 'typical' phages," said study author Jill Banfield, professor of earth and planetary science at the University of California, Berkeley, to Gizmodo.
Banfield and her colleagues said they identified more than 300 different types of phages, all with DNA larger than 200,000 base pairs. The largest one was more than 735,000 base pairs, which is more than 10 times that of the average virus base-pair count.
Called "huge phages" by the team, these phages seem to have genes one normally finds in living organisms and cells, which are genes that should allow them to perform amazing tricks.
Applications for CRISPR
A multitude of the huge phages have genes that are important to a system used by bacteria to fight viruses, known to the world as CRISPR. People generally think of CRISPR as a cool new gene-editing technology, but it actually comes from the ancient immune systems of bacteria (and another single-celled organism called archaea), used to slice up the DNA of hostile viruses intent on infection and ruin. CRISPR-relevant genes like these could be made to help huge phages amplify their host's defenses, Badem Al-Shayeb said to Gizmodo, by targeting and destroying other viruses competing for the same host cell.
In a time of widespread panic about the infectious coronavirus, it's easy to forget how the study of viruses we fear the most also ultimately increases our power against them. Clearly the micro-world of huge phages are going to take the human world by storm.
For the better, let's hope.