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Published on: January 17, 2018
Prokaryotes: the unseen majority
W B Whitman1, D C Coleman, W J Wiebe
1Department of Microbiology, University of Georgia, Athens GA 30602, USA. whitman@uga.cc.uga.edu
Summary
Prokaryotes significantly impact global carbon cycles, holding substantial cellular carbon and nutrients. Their vast numbers and rapid turnover highlight their crucial role in Earth
Area of Science:
- Microbiology
- Biogeochemistry
- Environmental Science
Background:
- Prokaryotes represent a vast and underappreciated component of Earth's biomass.
- Estimates suggest prokaryotic carbon constitutes 60-100% of plant carbon, nearly doubling global living organism carbon estimates.
- Prokaryotes are major reservoirs of essential nutrients like nitrogen (N) and phosphorus (P).
Purpose of the Study:
- To estimate the global abundance and biomass of prokaryotes.
- To assess the contribution of prokaryotes to global carbon, nitrogen, and phosphorus cycles.
- To determine the distribution and turnover rates of prokaryotes across different Earth environments.
Main Methods:
- Compilation and analysis of existing data on prokaryote cell numbers and biomass.
- Estimation of prokaryotic carbon, nitrogen, and phosphorus content.
- Calculation of prokaryote distribution in various habitats (ocean, soil, subsurface) and estimation of turnover times.
Main Results:
- Global prokaryote estimates: 4-6 x 10^30 cells, 350-550 Pg C, 85-130 Pg N, 9-14 Pg P.
- Prokaryotic carbon nearly doubles estimates of total living biomass carbon.
- Prokaryotes are the largest nutrient pools, with rapid turnover in oceans and soil, but slow in subsurface environments.
Conclusions:
- Prokaryotes are a dominant force in global biogeochemical cycles.
- Incorporating prokaryotic biomass into global models is essential for accurate Earth system assessments.
- The immense population size and rapid growth of prokaryotes drive significant genetic diversity and ecosystem functions.
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