Heterotrophic Archaea dominate sedimentary subsurface ecosystems off Peru.
Studies of deeply buried, sedimentary microbial communities and associated biogeochemical processes during Ocean Drilling Program Leg 201 showed elevated prokaryotic cell numbers in sediment layers where methane is consumed anaerobically at the expense of sulfate. Here, we show that extractable archaeal rRNA, selecting only for active community members in these ecosystems, is dominated by sequences of uncultivated Archaea affiliated with the Marine Benthic Group B and the Miscellaneous Crenarchaeotal Group, whereas known methanotrophic Archaea are not detectable. Carbon flow reconstructions based on stable isotopic compositions of whole archaeal cells, intact archaeal membrane lipids, and other sedimentary carbon pools indicate that these Archaea assimilate sedimentary organic compounds other than methane even though methanotrophy accounts for a major fraction of carbon cycled in these ecosystems. Oxidation of methane by members of Marine Benthic Group B and the Miscellaneous Crenarchaeotal Group without assimilation of methane-carbon provides a plausible explanation. Maintenance energies of these subsurface communities appear to be orders of magnitude lower than minimum values known from laboratory observations, and ecosystem-level carbon budgets suggest that community turnover times are on the order of 100-2,000 years. Our study provides clues about the metabolic functionality of two cosmopolitan groups of uncultured Archaea.
Biddle
Jennifer F
JF
Pennsylvania State Astrobiology Research Center, Pennsylvania State University, University Park, PA 16802, USA.
Lipp
Julius S
JS
Lever
Mark A
MA
Lloyd
Karen G
KG
Sørensen
Ketil B
KB
Anderson
Rika
R
Fredricks
Helen F
HF
Elvert
Marcus
M
Kelly
Timothy J
TJ
Schrag
Daniel P
DP
Sogin
Mitchell L
ML
Brenchley
Jean E
JE
Teske
Andreas
A
House
Christopher H
CH
Hinrichs
Kai-Uwe
KU
D000693:Anaerobiosis; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D017753:Ecosystem; D004734:Energy Metabolism; D019015:Geologic Sediments / Q000382:microbiology*; D008055:Lipids / Q000737:chemistry / Q000302:isolation & purification; D008386:Marine Biology; D008969:Molecular Sequence Data; D010568:Peru; D010802:Phylogeny; D019642:RNA, Archaeal / Q000235:genetics / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000302:isolation & purification
D008055:Lipids; D019642:RNA, Archaeal; D012336:RNA, Ribosomal, 16S; D002244:Carbon