Lan and Tu: "Information Processing in Bacteria"

Lan, Ganhui, & Yuhai Tu. “Information processing in bacteria: memory, computation, and statistical physics: a key issues review.”  Reports on Progress in Physics. US National Library of Medicine, National Institutes of Health.  2016 May, Volume 79, Number 5, 79(5):052601. doi: 10.1088/0034-4885/79/5/052601. Epub 2016. Accessed 10 Dec 2016. <>

In order to survive, biological systems adapt as organisms store memory to inform decisions that will help organisms survive: 

"Biological systems need to sense and process information from their environment in order to make decisions vital for their survival and growth. Like a computer, a cell not only needs to take the input information, it also has the ability to store information (memory) and to use the memory together with the input to compute an output (decision) that will enhance its survival and/or growth. In this review, we use the simple E. coli chemotaxis signaling system as an example to demonstrate the ability of a cell to maintain an accurate memory and to compute. In a loose sense, the E. coli chemotaxis pathway can be considered as a probabilistic Turing machine" (Lan n.pag). 

Information theory suggests that data from biological networks data reveals an information architecture that can provide insights into how parts of the network correlate and relate to network performance: 

“Due to the inherent noise in biological systems, the measured input-output dependence is often noisy. These noisy data can be analysed by using powerful tools and concepts from information theory such as mutual information, channel capacity, and maximum entropy hypothesis. This information theory approach has been successfully used to reveal the underlying correlations between key components of the biological networks, to set bounds for the network performance, and to understand possible network architecture in generating the observed correlations" (Lan n.pag). 

From Section 3, "The thermodynamic cost of maintaining an accurate memory":

"Adaptation is a fundamental function of living systems. For E. coli, it encodes a working memory, which is crucial for gradient sensing in chemotaxis. However, despite its well-known benefits, the cost of accurate adaptation in a noisy environment (both internal and external) has been elusive. It was not clear how much, if any, energy needs to be consumed for a given level of adaptation accuracy; and what is the thermodynamic limit of such dissipative living system?" (Lan n.pag).
"In general, we argue that considering biological systems as information processing machines may provide one unifying perspective in studying dynamics of biochemical networks, their physical limits, and the underlying design principles" (Lan n.pag).


Katie Ancheta