Stripped Down to the Bare Essentials

Abstract

EVOLUTION Coupling the belief that early forms of life arose under inhospitable conditions (high temperatures and low oxygen) to the reasonable assumption that simpler organisms are more ancient than complex ones would place Methanopyrus kandleri near the base not only of the “black smoker” chimneys in the deep ocean but also of the archaeal tree. Nevertheless, having sequenced the genome of this organism, which is capable of growing on H2 and CO2 at temperatures above 100°C, Slesarev et al. conclude just the opposite. A substantial fraction of the M. kandleri proteins can also be found in two other archaeal methanogens, and this trio consistently forms a cluster in trees of archaeal species when analyzed on the basis of genes and operons. Unlike its relations, however, M. kandleri shares only a small percentage of its proteome with bacteria, which the authors suggest may reflect having had fewer opportunities for lateral transfer in its extreme environment, and its present impoverished state (in terms of gene number and signal transduction pathways) appears to be a consequence of life as a minimalist.— GJC Proc. Natl. Acad. Sci. U.S.A. 99 , 4644 (2002).