Neutrons for Science and Industry

Thin film physics in bacterial biofilms and chocolate

by Dr Simon Titmuss (University of Edinburgh)

HS 3 (Physics Department)

HS 3

Physics Department


Bacteria and chocolate are two seemingly disparate systems. 

A link is provided by the presence of thin lipid films in the two systems and our use of neutron/x-ray scattering and reflectivity techniques to probe these thin films.

Chocolate is a dense suspension of solids, mainly sucrose, in a continuous triglyceride fat phase of cocoa butter, containing lecithin, which is mostly phospholipid, and in some cases the polymeric surfactant polyglycerolpolyricinoleate (PGPR). These surfactants reduce the yield stress and viscosity of molten chocolate, which is important in chocolate manufacture. I will discuss the methodology that we have used to investigate the structural basis for the observed rheology. 

Bacterial biofilms are surface-attached colonies of bacteria that can exert deleterious effects  on health and  industrial applications.  I will discuss two of the interfaces found in bacterial biofilms. 

The air/water interface of a B. Subtilis biofilm is decorated by the surface-active protein BslA, which forms a molecular rain coat, rendering the biofilm surface water repellent. We have used x-ray and neutron reflectivity to follow the self-assembly of this molecular rain coat. 

Zooming in further, cytoplasmic bacterial cell membranes are decorated by various protein ion channels, including MscL (mechanosensitive ion channel of large conductance). These mechanosensitive ion channels act as safety valves to protect cells against osmotic shock. I will describe our efforts to develop experimental methodologies to probe the gating of these ion channels in model bacterial membranes using neutron reflectivity and scattering.

I emphasize that at no point have we mixed bacteria and chocolate.

Organized by

Dr. Alexandros Koutsioumpas
Dr. Markos Skoulatos