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Research

Arnosti Lab

Microbial Biogeochemistry

   

Our lab focuses on three key topics:

  1. Microbially-driven carbon cycling in the ocean.

  2. The relationship between chemical structure and reactivity of organic matter.

  3. The relationships between microbial community composition and function, including factors that control distinct microbial mechanisms of carbon cycling. (See also Arnosti et al. 2018 and Reintjes et al. 2019 for the distinction between selfish, sharing, and scavenging bacteria.)

 

We use chemical and microbiological methods to investigate the chemical structure and reactivity of high molecular weight organic matter, and the role of microbial communities in organic matter degradation in sediments, seawater, and rivers.

Our work fits into the larger framework of carbon cycling on a global scale: heterotrophic microbes play key roles in the transformations, decomposition, and recycling of marine organic carbon, and are believed to be active in nearly all known marine environments, ranging from surface waters to sea ice to anoxic sediments, hydrothermal systems, and the deep biosphere.        

 

Three major unknowns of microbially-driven carbon cycling:

  1. The nature of the extracellular enzymes used to initiate carbon cycling.

  2. The identity of the microbes.

  3. The 3D structure of the substrate.

 

Most organic matter in marine systems is initially produced as macromolecules (proteins, polysaccharides, lipid complexes, nucleic acids) whose production and structure are reasonably well understood. The processes by which these macromolecules are transformed and (for the most part) ultimately remineralized to CO2 by marine microbes, however, are largely unknown. The identities and specific activities of the vast majority of microorganisms that catalyze these processes are only beginning to be discovered. Our goal therefore is to understand these transformations, and to identify key organisms and processes involved.

We conduct laboratory studies to investigate specific carbon degradation processes, and we develop new methods to study specific aspects of carbon cycling. We then apply these methods in the field to investigate  carbon cycling under a wide range of conditions. Much of our work is carried out in collaboration with colleagues at UNC (Teske lab) as well as with colleagues at other institutions in the U.S. and abroad.