Through intensive cultivation efforts, members of our group have been isolating and characterizing eukaryotic microplankton from tropical coastal waters of Oʻahu and the oligotrophic open ocean. Many are mixotrophic flagellates that both photosynthesize and feed on other plankton. Some have developed symbiotic relationships with nitrogen-fixing bacteria, a critical adaptation that allows them to survive in nutrient-poor waters of the oligotrophic gyres. Investigation of these new strains is helping us understand the ecology and physiology of some of the most important organisms on our planet: the open ocean phytoplankton that are the foundation of the marine food web and are responsible for much of the daily oxygen production on our planet.

Everything that lives in the ocean has to contend with viral infections, including the phytoplankton. By challenging cultures of phytoplankton with viruses harvested from the ocean, we have managed to isolate a diverse suite of new algal viruses of every genome type (double- or single-stranded, DNA or RNA). This effort has led to many surprises, including the discovery of a giant virus with an astonishing array of genes for sugar metabolism, the first observation of fermentation genes in a virus, and the discovery of new algal viruses whose closest relatives infect plants or animals.

Microbes are constantly growing in our waterways, soils and oceans, but their numbers are kept in check by microscopic grazers that eat them and viruses that infect and lyse them. Viruses donʻt always simply kill the cells they infect, however, as bacteria and archaea have defense mechanisms that allow them to fight off some infections. In other cases, a virus and a cell will enter into a mutually beneficial symbiotic relationship in which the viral genome stays within the host cell expressing genes that provide the host with advantages over its competitors. Viruses can also transfer DNA from one cell they have infected into another, thereby creating genetic variation on which natural selection will act. We are isolating and characterizing microbes and their viruses to better understand the many different ways that viruses contribute to the ecology and evolution of microorganisms.

Life permeates the ocean from the sea surface to the seafloor sediments...and beyond! Below the layer of sediment on the seafloor lies the ocean basement, a basaltic rock foundation. Deep seawater enters the ocean basement through cracks and fissures and percolates through, eventually returning to the deep ocean via vents and seeps. This basement aquifer is an enormous and underexplored habitat for marine microbial life. To better understand the ecological and evolutionary pressures on microbial life in this habitat, we have been sampling basement fluids from hundreds of meters deep into the rock via specially designed well heads called CORKS. We have been documenting the abundance and diversity of viruses deep in the ocean basement using microscopy and metagenomic analyses.

Bacteria are a critical part of all aquatic ecosystems and master recyclers. They decompose organic matter from dead or dying organisms and return nutrients to the water for phytoplankton to use again. Some of the naturally occurring bacteria in coastal waters, however, are also capable of causing opportunistic infections in humans. Some bacteria in the genus Vibrio, for example, thrive in warm brackish waters, but, if exposed to an open wound or ingested, are capable of replicating in humans. Hawaiʻi, likely because of its year-round warm weather, has the highest per capita incidence of vibrio infections from recreational water exposure in the United States. To better understand and predict the risks from infection by Vibrio vulnificus, one of the more serious pathogens, we have been isolating, characterizing, and modeling the ecology of strains of this bacterium in the coastal waters of Oʻahu. We are also isolating viruses that infect and kill Vibrio vulnificus, which may prove useful for treating infections in humans.