The human large bowel ("gut") is colonized by an extremely dense
population of bacteria, collectively termed the microbiota or "gut
Recent research indicates that the microbiota is important for human
health and nutrition and has been linked with auto-immune diseases,
cancer and obesity. The function and composition of the microbiota is
dependent on the ability of individual micro-organisms to acquire
nutrients such as starch and other dietary polysaccharides in the highly
competitive environment of the human large bowel.
‘The first three-dimensional atomic structure of substrate binding protein (SusCD) complexes has been determined by researchers. They have also established how the nutrients are transported into the bacterial cell.’
This process of nutrient acquisition is carried out by protein
machines embedded in the bacterial cell envelope. In many microbiota
members, this machine is a two-component complex consisting of a
substrate binding protein (termed SusD) and a channel-forming transport
protein (termed SusC).
The researchers, led by Professor Bert van den Berg
and Dr. David Bolam from the Institute of Cell and Molecular
Biosciences at Newcastle University and with support from collaborators
at Jacobs University Bremen, report that they have
purified and determined the first three-dimensional atomic structures of
SusCD complexes by X-ray crystallography and have established how the
nutrients are transported into the bacterial cell.
The SusCD complexes function like a pedal bin, with SusD forming the
lid on the SusC bin. In the absence of substrate, the lid can open.
After substrate capture, the lid closes and the substrate moves into the
bin for transport into the cell.
The study provides fundamental insights into the functioning of the
microbiota and understanding the human-gut flora symbiosis. Results such
as these are a timely and necessary complement to most current
microbiota research, which is largely focused on answering systems
biology questions such as "who is there and when?".
By linking mechanistic and systems biology, the study could also
provide insights to manipulate the composition of the microbiota via
interference with critical nutrient uptake processes.