The
human large bowel ("gut") is colonised by an extremely dense
population of bacteria, collectively termed the microbiota or "gut
flora."
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.
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
team at Newcastle University today 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.
For
further details, see:
Posted by Dr. Tim Sandle
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