QLS Guest Seminar - Friday 30 September 2016

[Quantitative Life Sciences]

QUANTITATIVE LIFE SCIENCES GUEST SEMINAR

Friday, 30 September 2016 at 15:00

ICTP, Central Area, 2nd floor, old SISSA building

Speaker: Subrata Dev - S.N. Bose National Centre for Basic Sciences, India

Title: " Optimal conditions of external medium and intracellular 
environment for efficient chemotactic performance in E. coli"

Abstract:
Chemotaxis is the directed motion of organisms in response to the 
chemical gradient. When
E. coli bacterium is placed in a medium with a concentration gradient of 
nutrient, it moves up the
gradient and accumulates in regions with higher nutrient concentration. 
The efficient chemotactic
performance is characterised by the ability to find the favorable region 
quickly and to localize in the
favorable region at large times. We investigate how this efficiency 
depends on the external
environment and the internal biochemical pathway of the E.coli cell. 
When the cell is in a medium
where the nutrient is diffusing and the form of nutrient profile is 
Gaussian, we find that there exists an
optimal width of the profile for which the search time becomes minimum. 
In the case when the nutrient
diffusion and cell movement occurs over comparable time-scales, there 
exists an optimum value of the
nutrient diffusivity for which the search time becomes minimum. The 
simulation results in a phenotype
model agree well with our analytical calculations in a related 
coarse-grained model where the
bacterium behaves like a random walker with position dependent drift 
velocity and diffusion
coefficient. In a single cell chemotaxis the internal biochemical 
pathway involves noise due to the
fluctuations present in the number of different molecules taking part in 
the reactions. This noise plays a
very crucial role on the chemotactic performance of E. coli bacterium. 
We find that in the long time
limit the localization and the uptake, i.e. the total nutrient 
intercepted along its trajectories, becomes
maximum for an optimum value of the noise strength. We discuss a simple 
mechanism to explain this
effect.

Web: http://indico.ictp.it/event/8023/

-- 
Erica Sarnataro
Group Secretary
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
e-mail:qls at ictp.it