Lysis vs lysogeny: phages tap into quorum-sensing as control mechanism

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A bacteriophage, VP882, can listen in to bacterial communications and use this information to decide whether to initiate a lytic or lysogenic lifecycle, according to new research from Bonnie Bassler and Juston Silpe (Princeton University, NJ, USA).

Bassler explained: “The idea that a virus is detecting a molecule that bacteria use for communication – that is brand-new.”

Bacteriophages have the choice of two lifecycles upon infecting bacteria – lytic or lysogenic. The lytic option has an inherent risk, as if no other hosts are nearby “then the virus and all its kin just died,” explained Bassler.

However, the team discovered that bacteriophage VP882 has found a way to reduce this risk; by identifying quorum-sensing between bacteria the phage ups the chances that there are more new hosts nearby. For such different organisms to be able to detect and interpret each other’s signals is exciting, as Bassler commented: “Justin’s work shows that these quorum-sensing molecules are conveying information across kingdom boundaries.”

“He just started a brand-new field, the idea that there’s only one example of this cross-domain communication made no sense to us. Justin discovered the first case, and then, with his discovery in hand, he went looking more deeply and he found a whole set of viruses that harbor similar capabilities. They may not all be listening in to this quorum-sensing information, but it is clear that these viruses can listen in to their hosts’ information and then use that information to kill them.”

VP882 was discovered after Silpe found a new quorum-sensing gene in V. cholera and decided to search genome databases for that gene. In addition to being present in some related strians the database also reported that one virus, VP882, had this quorum-sensing gene.

Once VP882 was identified to have this ability, Silpe began to reengineer the virus to respond to other sensory inputs, so the phage killed on demand. The researchers have carried out three proof-of-concept tests on cholera, salmonella and E. coli demonstrating VP882’s ability to target these pathogens.

This is the first phage discovered that senses bacterial communication and uses this to inform whether it’s optimal to kill its host, in addition, VP882 has a broad host range making it a promising therapeutic tool.

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Sources: Silpe J, Bassler B. A host-produced quorum-sensing autoinducer controls a phage lysis-lysogeny decision. Cell. (2018); www.eurekalert.org/emb_releases/2018-12/pu-bte113018.php

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