Address for correspondence: Robert H. White, Department of Biochemistry (0308), Virginia Polytechnic Institute and State University, Blacksburg, VA 24061. Voice: +1-(540) 231-6605; fax: +1-(540) 231-9070. rhwhite{at}vt.edu
The development of an oxygenated atmosphere on earth resulted
in the polarization of life into two major groups, those that
could live in the presence of oxygen and those that could not—the
aerobes and the anaerobes. The evolution of aerobes from the
earliest anaerobic prokaryotes resulted in a variety of metabolic
adaptations. Many of these adaptations center on the need to
sustain oxygen-sensitive reactions and cofactors to function
in the new oxygen-containing atmosphere. Still other metabolic
pathways that were not sensitive to oxygen also diverged. This
is likely due to the physical separation of the organisms, based
on their ability to live in the presence of oxygen, which allowed
for the independent evolution of the pathways. Through the study
of metabolic pathways in anaerobes and comparison to the more
established pathways from aerobes, insight into metabolic evolution
can be gained. This, in turn, can allow for extra- polation
to those metabolic pathways occurring in the
Last
Universal
Common
Ancestor (LUCA). Some of the unique and uncanonical metabolic
pathways that have been identified in the archaea with emphasis
on the biochemistry of an obligate anaerobic methanogen,
Methanocaldococcus jannaschii are reviewed.
