Páginas: 4 (793 palabras) Publicado: 30 de agosto de 2011
Edited by Christopher B. Field, Carnegie Institution of Washington, Stanford, CA, and approved December 5, 2005 (received for review August 29, 2005)
For centuries, biologists have studied patternsof plant and animal
diversity at continental scales. Until recently, similar studies were
impossible for microorganisms, arguably the most diverse and
abundant group of organisms on Earth. Here, wepresent a continental-
scale description of soil bacterial communities and the
environmental factors influencing their biodiversity. We collected
98 soil samples from across North and SouthAmerica and used a
ribosomal DNA-fingerprinting method to compare bacterial community
composition and diversity quantitatively across sites. Bacterial
diversity was unrelated to site temperature,latitude, and
other variables that typically predict plant and animal diversity,
and community composition was largely independent of geographic
distance. The diversity and richness of soil bacterialcommunities
differed by ecosystem type, and these differences could
largely be explained by soil pH (r20.70 and r20.58, respectively;
P < 0.0001 in both cases). Bacterial diversity was highest inneutral
soils and lower in acidic soils, with soils from the Peruvian Amazon
the most acidic and least diverse in our study. Our results suggest
that microbial biogeography is controlled primarily byedaphic
variables and differs fundamentally from the biogeography of
‘‘macro’’ organisms.
biodiversity  microbial ecology  soil bacteria  terminal-restriction
fragment length polymorphismAlthough microorganisms are perhaps the most diverse (1, 2)
and abundant (3) type of organism on Earth, the distribution
of microbial diversity at continental scales is poorly understood.
Ecologistsdescribing microbial biogeography typically
invoke Beijerinck (4) from a century ago: ‘‘Everything is everywhere,
the environment selects.’’ However, few studies have
attempted to verify this...
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