期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：11
页码：1
DOI：10.1073/pnas.2100935118
出版社：The National Academy of Sciences of the United States of America
摘要：Heterotrophic microorganisms are fiendishly clever at degrading all shapes and sizes of organic compounds to extract the energy they need to build biomass. Every year marine phytoplankton fix ∼50 billion tons of carbon dioxide into organic matter, and every year marine heterotrophs respire nearly all of this organic matter back to carbon dioxide (1). Nearly all, but not all. With each spin of this carbon cycle, a small amount of organic matter escapes respiration and becomes sequestered in seawater, sediments, and soils. Over time, this small “leak” in the system leads to the accumulation of a vast reservoir of carbon; some 5 × 1019 kg of organic matter are thought to be sequestered in sedimentary rocks (2). This carbon sequestration has immense consequences for life on Earth, as illustrated by the change in climate we are now experiencing due in part to the transfer of a minute portion of this inventory from geologic reservoirs into the atmosphere. The question of why carbon is preserved at all has puzzled geochemists and biogeochemists for well over half a century. Why is organic matter production and consumption not coupled even more tightly? If the organic matter that ultimately accumulates in geologic reservoirs is synthesized by microbes in the first place, why cannot microbes degrade it? In soils and sediments minerals are thought to be an important part of the answer. Adsorption of organic matter onto mineral surfaces imposes a number of penalties on degradation: the extra energy cost of organic matter desorption, impediments to the movement of hydrolytic enzymes through the environment, and irreversible deactivation of enzymes by mineral surfaces, to name a few. Each of these penalties makes degradation less of an energy gain for consumers (3, 4). However, organic matter–mineral surface interactions alone cannot be the whole answer.
