They discovered that Z-genomes are actually much more widespread than previously thought. Zhao and her team analyzed sequences of the phages with the Z-genome and compared them to other organisms.

'People believed that this Z-genome was so rare,' Suwen Zhao, an assistant professor in the school of life science and technology at ShanghaiTech University and the senior author of one of the studies, said. They also found that this enzyme specifically excludes the A-nucleotide and always adds the Z instead.įor decades, the Z-genome was only known to exist in one species of cyanobacteria. The third group identified the enzyme responsible for assembling new DNA molecules from the parent DNA molecule: a DNA polymerase known as DpoZ. Other proteins then modify it so that it can be incorporated into DNA. Once the cyanophage injects its DNA into bacteria to replicate itself, a series of transformations take place: Those two proteins make a precursor Z-molecule and then convert the Z precursor molecule into the Z-nucleotide. The first two groups found two major proteins known as PurZ and PurB that are involved in making the Z-nucleotide. Factory ZĪll three research groups, using a variety of genomic techniques, identified a part of the pathway that leads to the Z-genome in bacteriophages. Now, two research groups in France and one in China have discovered another piece of the puzzle: how this Z-nucleotide ends up in the genomes of bacteriophages - viruses that invade bacteria and use its machinery to replicate. In the late 1980s, researchers found that this Z nucleotide actually gave the virus some advantages: it was more stable at higher temperatures, it helped one strand of DNA bind more accurately to the second strand of DNA after replication (DNA is double-stranded), and Z-DNA could resist certain proteins present in bacteria that would normally destroy viral DNA. In other words, a genetic alphabet that typically consists of ATCG in most organisms on our planet was ZTCG in these viruses.įor decades, this was a head-scratching discovery - as weird as spelling apples “zpples” - and little was known about how this one-letter substitution may have impacted the virus. In 1977, a group of scientists in Russia first discovered that a cyanophage, or a virus that invades a group of bacteria known as cyanobacteria, had substituted all of its As for the chemical 2-aminoadenine (Z).

Z-Virus by M.D. Khamil