|Like a world of its own, this sphere represents
all the known chemical reactions in the E. coli bacterium. The colorful
circles on the surface symbolize sets of densely interconnected reactions.
The lines between the circles show additional connecting reactions. The
shapes inside the circles are landmark molecules, like capital cities on
a map, that either act as hubs for many groups of reactions, are highly
conserved among species, or both. Molecules that connect far-flung reactions
on the sphere are much more conserved during evolution than molecules that
connect reactions within a single circle. This statistical cartography could
reveal insights about other complex systems, such as protein interactions
and gene regulation networks. Courtesy of Luis A. Nunes Amaral, a chemical
and biological engineer at Northwestern University. Featured in the August 16, 2005, issue of Biomedical Beat.
High res. image (2.2 MB TIFF)