Marine Microbial Chemical Ecology

Microorganisms are the engines that both drive Earth’s biogeochemical cycles and control health and disease states in macroorganisms. They are the ultimate ecosystem engineers, whether that ecosystem is a coral reef, a rice plant, or the human gut. Microbes (viruses, archaea, bacteria, and protists) thrive within complex communities and communicate via dissolved chemical cues. Thus, microbial ecology is chemical ecology. Our research seeks to understand the diverse chemical cues that drive interactions among marine microbes and their environment. Current projects include investigations into allelopathic interactions among marine cyanobacteria, identification of chemical cues released by virus-infected phytoplankton, and quantifying chemotactic responses of diverse bacteria and protists to exometabolites released by virocells at different stages of infection. Credit: Micheal Stehnach, Guasto Lab.


Virocells

Virocells, or virus-infected cells, are an often-overlooked component of microbial communities. It is estimated that approximately one third of marine microbes are virus-infected, existing in early stages of lytic viral infection or as lysogens (cells containing a lysogenic virus). Viruses have an incredible capacity to reprogram host metabolism during infection, rendering virocells biochemically and phenotypically distinct from their uninfected counterparts. Our research uses a combination of systems biology tools (genomics, transcriptomics, proteomics, and stable isotope assisted metabolomics) coupled with biochemical and photophysiological measurements and live-cell video microscopy to quantify molecular mechanisms and phenotypic manifestation of viral metabolic reprogramming, as well as virocell interactions with other marine microbes. Current projects include investigations into marine Synechococcus virocell metabolic reprogramming and interactions with heterotrophic bacteria and protist predators, virocell pigment biosynthesis and photosynthesis, and the role of virocells in cross-trophic carbon and nitrogen flux in marine plankton communities. Credit: PNNL (CC BY-NC-SA 2.0)


Cyanobacterial Biofilms

The term “open ocean” often brings to mind visions of vast expanses of water devoid of surfaces and structure. However, microorganisms exist at very different spatial scales than humans, and from a microbial perspective, even the open ocean may provide plentiful opportunities to find and form micron-sized structures. Biofilms are bacterial assemblages in which cells adhere to a surface or to each other, and are often encased within a self-protecting matrix comprised of polysaccharides, lipids, proteins, extracellular DNA, and viruses. Within pelagic environments microbes attach to other cells, to multicellular zooplankton, to non-living material, and to sinking particles that function as rich and diverse microbial habitats. Deciphering the mechanisms that control free-floating biofilm formation and subsequent sinking through epi- and mesopelagic environments is critical to understanding global ocean carbon cycling. Our research in this area is currently focused on identifying the molecular mechanisms of marine cyanobacterial biofilm formation and viral impacts on biofilm formation and longevity.