By: Bhawana Jain

Published on: February 6, 2017

Article Source: Texas A&M AgriLife Communications

Abstract: We humans make numerous decisions every day. But a team of scientists has discovered that the tiniest organisms like viruses also make decisions. In their research, the scientists found that the lambda phage decides what actions to take in its host, the E.coli bacterium. Hence, understanding the decision making process of these creatures could help us find out better treatments for few diseases.

Complete article:

Decision making is something which we do every day. But we’re not alone. Even the tiniest organisms like viruses also make certain decisions at times and decides what actions to take in their host, scientists have discovered recently. According to their research, understanding how viruses takes these decisions could lead us to better treatments for some diseases. The study was published on Feb. 6 in the journal Nature Communications.

In the study, Dr. Lanying Zeng and her team at Texas A&M AgriLife Research discovered how the lambda phage decides what actions to take in its host, the E. coli bacterium.

A lambda phage, also referred as a bacteriophage is a virus that attacks and replicates within a bacterial species like E. coli. Phages were first discovered over 100 years ago, but no one ever thought that even such tiniest organisms could make decisions. In a recent research, scientists at Texas A&M AgriLife Communications started to study how they can be used to attack disease-causing bacteria, especially strains which have become highly resistant to antibiotics. The research could open new ways for treating specific bacterial maladies.

The lambda phage is a virus that prefers to destroy E. coli bacteria, so it is a prime target for researchers. In tracking that target, Jimmy Trinh, a Zeng’s graduate student, developed a four-color fluorescence reporter system to track it at the single-virus level. This was combined with computational models devised by Dr. Gábor Balázsi, a biomedical engineer and collaborator at Stony Brook University in Stony Brook, New York, “to unravel both the interactions between phages and how individual phages determine” the fate of a cell.

To their surprise, what they found was not unlike the decision-making process of humans. Sometimes the lambda phage was found cooperating with others while at times competing.

“Instead of just the cell making a decision, we found the phage DNAs themselves also make decisions,” Zeng said.

Through the process they developed, the scientists were able to determine that timing played a role in decision-making.

Zeng explained that some phages can have two cycles of reproduction: lytic and lysogenic.

In the lytic cycle, viruses make full copies of themseves inside of a cell, say an E. coli cell. When the phage-infected bacterial cell becomes full of the replicating viruses, it bursts open and is destroyed. In the lysogenic cycle, the phage’s DNA recombines with the host’s genome, say a bacterium and both continue to reproduce as one. In short, lysis involves competition while lysogeny involves cooperation, she said.

So, understanding how and when a phage decides to “go lytic” on the pathogen is a key to using phages to destroy bacteria, Zeng said.

“Say you have two lambda phages that infect one cell,” she said. “Each phage DNA within the cell is capable of making a decision. We want to know how they make a decision, whether one is more dominant than the other, whether they have any interactions and compete to see who will win, or whether they compromise.”

“They may even coexist for some time and then finally choose one decision,” she said. “But the phage is making a subcellular decision — and that is very important. There could be a lot of implications.”

The four-color fluorescence reporter system helped the researchers visualize that many factors contribute to the decision and that “from the evolutionary point of view, the phages want to optimize their own fitness or survival,” she said. “So that is why they choose either lytic or lysogenic to maximize or optimize their survival.”The team identified some of the factors that led to competition and others that led to cooperation.

Zeng said because phage therapy is a growing field for seeking ways to treat bacteria, the results of this study will help other scientists advance their research.

“This is a paradigm for bacteriophages,” she said. “When we understand the mechanism of the decision more, that can lead to more applications and better characterization of other systems.”

Journal Reference:

Jimmy T. Trinh, Tamás Székely, Qiuyan Shao, Gábor Balázsi, Lanying Zeng. Cell fate decisions emerge as phages cooperate or compete inside their hostNature Communications, 2017; 8: 14341 DOI: 10.1038/ncomms14341