Viruses may monitor their hosts’ environment to spread more effectively

Interestingly, a phage never produces CtrA, so why does its DNA have a binding site for the protein? While looking for an answer to this question, the researchers discovered an unheard power of the phages.

Viruses are smarter than you think

Viruses may monitor their hosts' environment to spread more effectively

A scientist examining virus samples.

CtrA is actually associated with the formation of special outgrowths in bacterial cells. These outgrowths called flagella allow the microorganism to move and perform other actions such as adhesion, reproduction, and infecting a host. The researchers suggest that the binding site in a phage DNA is actually meant for the CtrA protein that controls flagella formation in their host bacteria.

Moreover, the occurrence of CtrA binding sites is not limited to a particular phage species. They are found in numerous types of flagellotropic phages. The findings explain why and how phages decide to attack only the bacteria that have developed flagella.

During the study, the researchers studied a phage that infects caulobacterales, an order that incorporates many gram-negative bacteria species. The special characteristic of caulobacter bacteria cells is that when plenty of food is available, they produce non-motile stalked cells. However, when there is a scarcity of food, the cells develop flagella and give rise to swarmers — bacteria that can freely move.

Viruses may monitor their hosts' environment to spread more effectively

One of the bacteriophages studied by the researchers.

The phage only infects the swarmer bacteria, but how is it able to distinguish between the different members of caulobacterales? Interestingly, the researchers found that CtrA protein decided whether the bacterial cell would divide to form stalkers or swarmers. They suggest that CtrA levels in a caulobacter enable the phage to choose the right host.

“We hypothesize the phages are monitoring CtrA levels, which go up and down during the life cycle of the cells, to figure out when the swarmer cell is becoming a stalk cell and becoming a factory of swarmers, and at that point, they burst the cell, because there are going to be many swarmers nearby to infect,” one of the authors and computational biologist at University of Maryland Baltimore County, Ivan Erill told PhysX.

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