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Speaker: Dr. Nicolo Michelusi, University of Southern California, Los Angeles, CA
Title: Electron transfer and cell energetics in bacterial cables: modeling and information theoretic aspects
Abstract:
Microbial communities play a significant role in bioremediation, plant growth promotion, human and animal digestion. Understanding how bacteria communicate and react/adapt to these signals is fundamental in order to engineer bio-nano networks and devices, and to control the growth of microbial fuel cells, which are posed to be the engines of renewable energy. While bacterial communication via molecular diffusion is well known and documented in the literature, electron transfer occurring in living cells and its role in cell-cell interaction is less understood.
In the first part of this talk, a novel stochastic queuing model of single cells and bacterial cables is presented, which links electron transfer to the energetic state of the cells. The model is also extensible to larger communities, by allowing for electron transfer between neighboring cells. The parameters of the stochastic queuing model are fit to experimental data available in the literature, and it is shown that the model tightly reproduces experimental measurements. In the second part, information theoretic aspects of communication over a bacterial cable are investigated, under the assumption of full channel state information (CSI). A compact state space representation is achieved by modeling the cable as an electron queue, with state given by the number of electrons within the cable, i.e., the sum of the state of the electron pools of each cell. This model effectively captures the overall effect resulting from clogging occurring locally within the cable due to ATP saturation. Unlike molecular diffusion, it is shown that communication via electron transfer introduces a new wellness constraint in addition to the information dimension; hence, the optimal input signal balances a tension between achieving high instantaneous information rate, and inducing wellness of the cable such that cells do not die. By exploiting the coupling between information-wellness, it is proved that the optimal signaling is binary, i.e., the encoder transmits at either maximum or minimum intensity, as dictated by the physical constraints, and has smaller average intensity than that given by the myopic policy, which greedily maximizes the instantaneous information rate.
This work represents a first contribution towards the design of electron signaling schemes in complex microbial structures, e.g., bacterial cables and biofilms, where the tension between maximizing the information transfer and guaranteeing the wellness of the overall bacterial community arises, and motivates further research on the design of more practical schemes, where CSI is only partially available.
Speaker Bio:
Dr. Nicolo Michelusi received the B.Sc. degree with honors, M.Sc. degree with honors and Ph.D. degree in Electrical Engineering from University of Padova, Italy, in 2006 and 2009, and 2013 respectively. Additionally, he received a second M.Sc. degree in Telecommunication Engineering from Technical University of Denmark in 2009, under the T.I.M.E. double degree program (www.time-association.org). In 2011, he was a visiting research scholar at University of Southern California in Urbashi Mitra's group and in Fall 2012, he was a visiting research scholar at Aalborgh University, Denmark, where he worked with Prof. Petar Popovski. He is currently a postdoctoral research fellow at the Ming Hsieh Department of Electrical Engineering, University of Southern California, USA, working with Prof. Urbashi Mitra. His research interests are in the areas of wireless communications, cognitive networks, energy harvesting, distributed estimation and adaptive control for wireless networks, modeling and design of bacterial systems. He is the recipient of a scholarship from the Fondazione Ing. Aldo Gini (2010) and he was awarded the Toni Mian scholarship for the best Master's Thesis in Information Engineering from University of Padova, Italy in March 2010. In 2013, he was awarded the grant “Isabella Sassi Bonadonna” from AEIT (Italian association of electrical engineering).
