Chapter 7
Lithotrophic (“Stone-Eating”) Microbes
Provide the Foundation for Deep
Subsurface Ecosystems
Thomas L. Kieft
Abstract Those of us who are microbiologists have no trouble thinking of microbes
as the most important and indeed the most fascinating of all organisms. They’re the
center of our world. They’re more numerous (~10
30 individuals) than any other
organisms on Earth ([Whitman WB, Coleman DC, Wiebe WJ, Proc Natl Acad Sci
USA 95:6578-6583, 1998]; [Kallmeyer J, Pockalny R, Adhikari RR, Smith DC, D’
Hondt, Proc Natl Acad Sci USA 109:16213-16216, 2012]), and they’re vastly more
diverse than the (some say) more charismatic macroorganisms (Locey KJ, Lennon
JT, Proc Natl Acad Sci USA 113:5970-5975, 2016). Anthropocentric types may be
surprised to learn that a human adult holobiome (a holistic view of a person as a
consortium) is comprised of a trillion or more human cells and that an even greater
number of microbes are living in and on each of us, providing myriad biochemical
and protective advantages. They outnumber us on almost any scale and in every
environment, whether we’re looking at a gram of soil, a ml of seawater, our own
bodies, or the entire biosphere. However, among all the possible environments for
considering the supremacy of microbes, my own favorite and my choice for demonstrating that microbes are indeed the “foundation stone” is the deep terrestrial
subsurface, i.e., very deep groundwater, the deepest, least investigated, and largest
biome on Earth.
7.1 Foundation
We can start with “foundation” as a descriptor. One meaning of this term is the
beginning or origin. The first life on Earth was unquestionable microbial, but where
did this life arise? Multiple candidate environments have been posited, e.g.,
Darwin’s “warm little pond,” Yellowstone-like thermal springs, and deep-sea hydrothermal vents but also the terrestrial deep subsurface (Trevors 2002). The subterranean world has a number of attractive features for origin of life theories: it has water
T. L. Kieft (*)
Biology Department, New Mexico Institute of Mining and Technology, Socorro, NM, USA
e-mail: thomas.kieft@nmt.edu
© Springer Nature Switzerland AG 2021
C. J. Hurst (ed.), Microbes: The Foundation Stone of the Biosphere, Advances in
Environmental Microbiology 8, https://doi.org/10.1007/978-3-030-63512-1_7
131
Lithotrophic (“Stone-Eating”) Microbes
Provide the Foundation for Deep
Subsurface Ecosystems
Thomas L. Kieft
Abstract Those of us who are microbiologists have no trouble thinking of microbes
as the most important and indeed the most fascinating of all organisms. They’re the
center of our world. They’re more numerous (~10
30 individuals) than any other
organisms on Earth ([Whitman WB, Coleman DC, Wiebe WJ, Proc Natl Acad Sci
USA 95:6578-6583, 1998]; [Kallmeyer J, Pockalny R, Adhikari RR, Smith DC, D’
Hondt, Proc Natl Acad Sci USA 109:16213-16216, 2012]), and they’re vastly more
diverse than the (some say) more charismatic macroorganisms (Locey KJ, Lennon
JT, Proc Natl Acad Sci USA 113:5970-5975, 2016). Anthropocentric types may be
surprised to learn that a human adult holobiome (a holistic view of a person as a
consortium) is comprised of a trillion or more human cells and that an even greater
number of microbes are living in and on each of us, providing myriad biochemical
and protective advantages. They outnumber us on almost any scale and in every
environment, whether we’re looking at a gram of soil, a ml of seawater, our own
bodies, or the entire biosphere. However, among all the possible environments for
considering the supremacy of microbes, my own favorite and my choice for demonstrating that microbes are indeed the “foundation stone” is the deep terrestrial
subsurface, i.e., very deep groundwater, the deepest, least investigated, and largest
biome on Earth.
7.1 Foundation
We can start with “foundation” as a descriptor. One meaning of this term is the
beginning or origin. The first life on Earth was unquestionable microbial, but where
did this life arise? Multiple candidate environments have been posited, e.g.,
Darwin’s “warm little pond,” Yellowstone-like thermal springs, and deep-sea hydrothermal vents but also the terrestrial deep subsurface (Trevors 2002). The subterranean world has a number of attractive features for origin of life theories: it has water
T. L. Kieft (*)
Biology Department, New Mexico Institute of Mining and Technology, Socorro, NM, USA
e-mail: thomas.kieft@nmt.edu
© Springer Nature Switzerland AG 2021
C. J. Hurst (ed.), Microbes: The Foundation Stone of the Biosphere, Advances in
Environmental Microbiology 8, https://doi.org/10.1007/978-3-030-63512-1_7
131