The investigator will develop a high-throughput viral-tagging method to investigate virus-host interactions in natural marine communities. In this approach, cultured or wild viruses are tagged by fluorescent labeling of their nucleic acid and allowed to adsorb to cells, thereby labeling the cells for differential sorting of viral-tagged cells by flow cytometry. Preliminary experiments using this method to detect, sort, and identify ocean microbes with attached viruses (i.e., viral-tagged cells) have been accurate and specific, showing distinct fluorescent shifts for viral-tagged target host cell populations and greatly reduced tagging of non-host cells.

This project will develop and rigorously evaluate this viral-tagging method for use with wild populations of viruses and microbes. First, additional systematic characterization of viral-tagging methodology with cultured virus-host pairs will be needed before application to wild populations. The investigator will use representatives of the three major types of marine DNA viruses with ecologically important host cell lineages to evaluate the effects of variable cell physiological states, experimental conditions, and host specificity on viral-tagging efficiency and signal. In addition, cryopreservation is critical for use of this method at remote sites. The investigator will test various cryopreservation techniques for impact on viral-tagging signatures and on downstream molecular biology. Parallel challenges face single-cell genomic researchers, making intellectual cross-fertilization desirable and likely. Finally, in experiments using cultured hosts as "hooks" to capture wild viral diversity, one must enrich for viral DNA after sorting viral-tagged cells. Based on stable isotope probing protocols, the investigator will test using cultured "bait" microbes grown on a 13C-labeled substrate to create heavy host DNA, thus allowing density-gradient separation of host from viral DNA. Light viral DNA is then linker-mediated amplified and pyrosequenced to reveal the host-specific viral metagenome.

Broader impacts: An experimentally validated viral-tagging method offers to alleviate three bottlenecks in understanding virus-microbe interactions. Specifically, the investigator anticipates that the method would allow a researcher to perform high-throughput experiments that could (1) map the in situ host range of a virus, (2) define the natural range of viruses that infect a given host, and (3) enable targeted metagenomic sequencing to further uncover the myriad ways that viruses impact microbial metabolism in the wild. Such advances would be useful across fields of viral and microbial ecology, as well as to biogeochemists and ecological modelers seeking population-scale datasets. A post-doctoral researcher will receive significant methodological training in advanced flow cytometry and molecular biological methods, as well as the opportunity to gain experience in grant and paper writing, teaching and cross-discipline and cross-cultural collaboration through collaboration with a Fulbright scholar and a systems administrator to enable high throughput data analysis pipelines to be established.

National Science Foundation (NSF)
Division of Ocean Sciences (OCE)
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David L. Garrison
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University of Arizona
United States
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