New study finds that the virus may have "eyes and ears" for us.

New research led by Columbia University, published in Frontiers in Microbiology, shows that viruses are using information from the environment to "decide" when to remain stable within the host body, when to multiply and explode, killing host cells
.

Ivan Erill, a professor of biological sciences and senior author of the new paper, said that the ability of viruses to perceive their environment, including the elements produced by their hosts, adds another layer of complexity
to virus-host interactions.

Not a coincidence

The new research has focused on bacteriophages — viruses that infect bacteria, often referred to simply as "bacteriophages
.

Even more surprising, Erill and the paper's first author, Elia Mascolo, a doctoral student in Erill's lab, found through detailed genomic analysis that these binding sites are not present only in a single phage, or even in a single group of
phages.

The ability to monitor CtrA levels "has been invented many times during evolution by different bacteriophages infected with different bacteria," Erill said
.

Time is everything

Another problem with this story is that the CtrA binding site in the first bacteriophage discovered by the team was infected with a special group of bacteria
called Caulobacterales.

Because bacteriophages can only infect cluster cells, when there are many cluster cells available for infection, only bursting out of the host is in their best interest
.

So, "we assume that phages are monitoring CtrA levels, which fluctuate up and down over the life cycle of the cell to determine when swarm cells become stalk cells and become colony factories," Erill said, "At that time, they rupture the cells because there will be many colonies nearby that need to be infected
.

Unfortunately, the method of proving this hypothesis is labor-intensive and extremely difficult, so it's not part of this latest paper — though Eryl and his colleagues hope to solve the problem in the
future.

"Everything we know about bacteriophages, and every evolutionary strategy they have developed, has been shown to translate into viruses
that infect plants and animals," he said.

There are other documented examples of phages monitoring the environment in interesting ways, but none include so many different bacteriophages using the same strategy to fight so many bacterial hosts
.

The new study is "the first broad demonstration that bacteriophages can listen for what's happening inside cells, in this case, from the perspective of cell development," Erill said
.

New treatment pathways

The study's key conclusion is that "viruses use cellular information to make decisions," Erill said, "and if it happens in bacteria, it will almost certainly happen in plants and animals as well, because if it's a meaningful evolutionary strategy, evolution will find out and exploit it
.

For example, to optimize its survival and replication strategies, an animal virus might want to know what kind of tissue it is in, or how strongly
the host responds to its infection.

"If you're developing an antiviral drug and you know the virus is listening for a particular signal, then maybe you can trick the virus
," Erill said.

essay

The transcriptional regulator CtrA controls gene expression in Alphaproteobacteria phages: Evidence for a lytic deferment pathway