My research interests have varied over the years as I was fortunate to be continuously exposed to new ideas, people and ecosystems. However, I have always been interested in the ecology and evolution of natural systems. In particular, I am currently focused on how ocean viruses, as tiny but abundant biological entities, impact global biogeochemical cycles through interactions with their microbial hosts' core metabolic functions.

My research aims to leverage an experimental model-systems approach with the application of modern techniques as phenomenologically-revealing windows into 'wild' viral populations. Three research directions in my lab include:

• Cyanophages: A model for studying global-scale photosynthetic host-phage interactions in the oceans
• Roseophages: Towards a new model for studying global-scale host-phage interactions in the oceans
• The Sea of Cortez Project: Developing new tools for interrogating 'wild' viral populations

The marine cyanobacteria Prochlorococcus and Synechococcus, globally important primary producers. In spite of their small size, these cyanobacterial cells are numerically dominant over vast areas of the "desert oceans" and are significant contributors to global carbon cycling. These were some of the earliest "ecological microbes" sequenced by the DOE JGI, which led to an understanding of the genomic underpinnings that are responsible for their ecological niches in the environment (Jed Fuhrman's News and Views, research articles Rocap et al. 2003, Palenik et al 2003).

Cyanobacterial viruses (cyanophages) are abundant, contribute to host mortality, and are thought to play a role in maintaining the extensive microdiversity of the marine cyanobacteria likely through killing the winner and through the movement of genes throughout the host population. Genomic sequencing has revealed that cyanophage genomes might best be descried as a standard "coliphage" chassis for structure and DNA delivery, decorated with a suite of niche- and host-defining genes. These latter genes include photosynthesis genes, even those from the core reaction center of photosynthesis, as well as genes likely involved in carbon metabolism, phosphate stress and novel nucleotide metabolism genes. Detailed studies of the core reaction center genes suggest that they are widespread among cyanophage isolates with a seemingly predictable distribution, they are expressed during infection, and parts of the viral copies of the genes have even been transferred abck into their hosts - thus cyanophages are acting as evolutionary drivers of the core reaction centers of the numerically dominant photosystems on the planet.

The oceanic cyanophage collection I developed at MIT contains over 1000 plaque-purified strains systematically isolated using a diversity of Prochlorococcus and Synechococcus host strains and source waters. Model cyanophage strains that have been used in experimental work have been characterized to varying degrees, while the remainder phage strains remain uncharacterized but an ideal reagent for large-scale screens.

At the University of Arizona, I will be continuing cyanophage work. If you are interested in cyanophages, please inquire about available projects.

For details on cyanophages from my thesis and post-doctoral work, please see these selected publications.

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The Roseobacter group has emerged as one of the most widespread abundant bacterial populations in coastal and open ocean surface waters. Representative strains from this group offer easily culturable and genetically manipulable laboratory strains that are of global ecological importance. Of interest to my 'roseophage hunt' would be isolating phages for hosts that are capable of some of the following: (1) carbon cycling through fixation of carbon dioxide using bacteriochlorophyll or carbon monoxide using the cox genes; (2) aromatic compound degradation; (3) sulfur cycling through DMSP-degradation enzymes and genes involved in the transformation of elemental sulfur; and (4) nitrogen cycling through nitrite reductase genes.

In an effort to better interpret cyanophage ecology and evolution, as well as to further elucidate viral roles in global-scale carbon, nitrogen and sulfur cycling, I hope to establish and develop a Roseobacter host-phage system parallel to that of the ocean cyanobacteria and their phages.

This work is in collaboration with Professor Mary Ann Moran at the University of Georgia and Dr. Forest Rohwer at SDSU.

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The young field of ocean viral ecology suffers from a lack of available tools that are needed to elucidate the inner workings of the complex, interconnected viral populations in the 'wild'. With the emergence of single-particle toolkits (e.g., microfluidics, flow cytometry, 'omics'), a new window into the variability of individuals in populations offers the promise of unprecedented insight.

The Sea of Cortez offers an accessible (3-4 hours drive from Tucson) and diverse aquatic field site for studying 'wild' microbial and viral populations. This proximity to such a site provides both the opportunity for seasonal characterization of these communities, as well as naturally complex source waters for evaluation of new tools for interrogating 'wild' populations.

This work is in collaboration with Dr. Phil Hugenholtz at the DOE Joint Genome Institute.

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