How much does information cost ?

Adviser: Yigal Meir

Student: יובל דהן

Abstract

This study investigates the behavior of bacteria and bacteriophages.
Bacteriophage, also called phages, are viruses that infect bacteria and archaea.
The infection process can occur in two different ways . In the first one, the phage injects its genetic material into the bacteria, and creates new virus particles, which are liberated by lysis (dissolution) of the cell. This process defined as lysis.
In the second process, the phage's genetic material enters the bacteria and behaves as a bacterial gene, and being replicated at each bacterial division, and transmitted to each of the bacterium progenies, which called lysogens. any new bacterium, which carries the virus's gene, has the capable of producing viruses. This process defined as lysogenic process.
It has been recently discovered , that while infecting, the virus can "choose" the infection process, namely, lysis or lysogen, according to its environment. During infection, a small molecule is released into the medium, and once it accumulates, it is affecting the lysis/lysogen decision of future generations phages. These molecules are being referred as arbitrium peptide.
This project describes a system model with a set of ODEs. In the model each phage will have a strategy, that defined by the probability of the phage's infection process to be lysogenic, below a given threshold of the peptides, and above it.
By using this model, we derived the optimal strategy, that maximize the phage lysogen amount.
Next, we found the price that phages are willing to pay for having the ability to read that information. that is, although reading that information allows the phage to adjust itself to the surrounding, it also has a negative impact. We estimated when that ability is no longer worthwhile.

1. A. Lwoff, “The life cycle of a virus”, Scientific American, Vol. 190(3), (1954), pp. 34-37.

2. Z. Erez, I. Steinberger-Levy, M. Shamir, et al. “Communication between viruses guides lysis-lysogeny decisions”. Nature, Vol. 541(7638), (2017), pp. 488-493.
Advertised on Jan. 7, 2021
Abstract added on Jan. 9, 2021
Abstract approved on Jan. 9, 2021 by Kovetz, Ely (kovetz)