No iron in Lyme

Iron sequestration is one way that human cells limit bacterial growth. In the 2 June issue of Science, Posey and Gherardini show that the Lyme disease pathogen, Borrelia burgdorferi, has responded by eliminating most genes that encode iron-requiring proteins, and substituting manganese for iron in the few metalloproteins that are left (Science 2000, 288:1651-1653). This is possible because the bacterium is an obligate parasite that lacks the enzymes for most biosynthetic pathways. As a result the bacterium grows happily with fewer than 10 atoms of iron present per cell.