Project Significance:

Created by George Rice, Montana State University

"The way that nutrients cycle through atmospheric, terrestrial, oceanic and associated biotic reservoirs can constrain rates of biological production and help structure ecosystems on land and in the sea. On a global scale, cycling of nutrients also affects the concentration of atmospheric carbon dioxide. Because of their capacity for rapid growth, marine microorganisms are a major component of global nutrient cycles. Understanding what controls their distributions and their diverse suite of nutrient transformations is a major challenge facing contemporary biological oceanographers. What is emerging is an appreciation of the previously unknown degree of complexity within the marine microbial community.
To understand how carbon and nutrients, such as nitrogen and phosphorus, cycle through the atmosphere, land and oceans, we need a clearer picture of the underlying processes. This is particularly important in the face of increasing anthropogenic nutrient release and climate change. Marine microbes, which are responsible for approximately half of the Earth's primary production, play an enormous role in global nutrient cycling."

(Arrigo, K.R., Marine microorganisms and global nutrient cycles. Nature 437, 349-355, 15 September 2005).

 Marine microbial interactions in the upper ocean.
Schematic representation of the ocean food web. On the left is the classic pathway of carbon and energy flow through photosynthetic Eukarya, to herbivores and on to higher trophic levels. Depicted on the right is the microbial food web, which uses energy stored in the non-living, detrital carbon pool to produce microbial biomass that can re-enter the classic pathway of carbon and energy flow. Cell-associated ectoenzymes (Ecto) enable bacteria to use high-molecular-weight (HMW) DOC in addition to the more traditional low-molecular-weight (LMW) and gaseous carbon substances. Also shown in the microbial food web are viral particles and Archaea. At the present time, there is only rudimentary knowledge of the role of Archaea in the oceanic food web. Shown at the bottom of this diagram is the downward flux of particulate carbon (and energy), which is now thought to fuel most subeuphotic zone processes. The classic algae-herbivore grazer pathway (left side) is most important in this regard. Adapted from Karl, D. M. Accurate estimation of microbial loop processes and rates. Microbiol. Ecol 28, 147-150 (1994).

Figure and legend from- DeLong E.F. & Karl D.M.Genomic perspectives in microbial oceanography. Nature 437, 336-342 (2005).

The central motivator underlying the specific questions asked in this microbial observatory is our shocking ignorance about marine microbes, these fundamentally important microscopic drivers of our planet's biogeochemistry.

As our countries and citizens grapple with the complex issue of global change, we must provide the best information we can about how marine microbes respond to and control atmospheric composition, and to do that we must begin by figuring out who is there and how the communities respond to "normal" environmental perturbations.

How to get there from here: Metagenomics

Recently, the merging of cultivation-independent gene sequences with contemporary genomic approaches (such as whole-genome shotgun sequencing) is providing a more comprehensive picture of the structure and function of indigenous microbial communities. Genomic approaches for studying natural microbial assemblages have been variously dubbed environmental genomics, population genomics, metagenomics or ecogenomics. Regardless of the moniker, all these approaches involve cultivation-independent genomic analysis of DNA extracted from naturally occurring microbial biomass.

(DeLong, E.F.,Microbial community genomics in the ocean. Nature Reviews/Microbiology 3, 459-69, June 2005).

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Copyright on all images and material by Ed DeLong, 2005.