    It wasn't until 2001 that this 1862 mystery was finally
solved. Seventeen-year-old Bill Martin was visiting Shiloh with
his family, where he heard about the strange glow. His mother,
microbiologist at the USDA Agricultural Research Service, had
studied luminescent bacteria, and Martin wondered if similar
bacteria might have been at work. With his friend Jon Curtis,
Martin researched Photorhabdus luminescens, a type of bacteria
that lives in the guts of parasitic nematodes. When nematodes
vomit up the glowing bacteria, P. luminescens kills the other
microbes living in the nematoad's host.  Normally, P.
luminescens couldn't live in the human body since it dies at
human body temperature. But Martin and Curtis, studying the
historical records and the conditions in Shiloh, realized that
the nighttime temperatures were low enough for the soldiers to
develop hypothermia, allowing the bacteria to thrive in their
bodies, kill off competing bacteria, and perhaps save the lives
of their human hosts.  For solving thi