to the website of Stephen Giovannoni's laboratory
in the Department of Microbiology at Oregon State University


Dr. Stephen Giovannoni has long been fascinated by ocean ecology. This fascination led to a scientific career pursuing the ecological role of bacterioplankton in the ocean's surface. Initially, the laboratory identified the major prokaryotic groups inhabiting this niche and, more recently, has cultivated individual species to explore the cellular adaptations that allow these organisms to affect biogeochemical cycles, especially carbon cycling.

Steve Giovannoni's laboratory is located at Oregon State University, a state supported institution with over 15,000 undergraduates. It is one of six universities in the nation to be designated a land, sea, and space grant institution. Oregon State University is awarded over $150 million annually for research, ranking it among an elite group of research universities nationally. Dr. Giovannoni teaches graduate and undergraduate courses, as well as providing undergraduate research training opportunities.

Research Directions


Bacterioplankton (planktonic marine bacteria) are among the most numerically abundant organisms on earth, yet, before 1990, they had not been identified. To solve this problem, we used 16S ribosomal RNA genes as genetic markers to map the diversity of uncultivated prokaryotes from natural plankton populations. This investigation involved gene cloning, DNA sequencing, and applications of molecular evolution theory and methods.

Our work led to the discovery of many groups of marine bacteria, the most well known of which is the SAR11 clade, which has become the main focus of our research.

Our research plan integrates field data from study sites on the Oregon Coast and the Western Sargasso Sea with "omic" approaches and pure culture experimentation, to understand how SAR11 genomes evolved, how they adapted to the ambient low nutrient conditions in the oceans, and how they interact with the immense oceanic dissolved organic carbon pool. SAR11 and other important bacterioplankton clades have global biogeochemical significance, but they are also fascinating because they appear to have been molded by unusual evolutionary circumstances that favor simplicity and efficiency. From this perspective, these cells might be viewed as the nearly optimal solutions to the problem of replicating in an ecosystem where nutrient concentrations hover near the extreme limits at which transport systems can function efficiently.


We continue to isolate key marine microorganisms into culture because many important properties of cells cannot be inferred from genome sequence alone and because complete genome sequences from cultured cells play an important role in the analysis of metagenomic data.

Our work is supported by the Gordon and Betty Moore Foundation, the National Science Foundation (grant no. 0237713), the Oregon Sea Grant, and the Murdock Charitable trust. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.