Certain benthic foraminifera thrive in marine sediments with low or undetectable oxygen. Potential survival avenues used by these supposedly aerobic protists include fermentation and anaerobic respiration, although details on their adaptive mechanisms remain elusive. To better understand the metabolic versatility of foraminifera, we studied two benthic species that thrive in oxygen-depleted marine sediments. Here we detail, vi...

Summary Developing transfection protocols for marine protists is an emerging field that will allow the functional characterization of protist genes and their roles in organism responses to the environment. We developed a CRISPR/Cas9 editing protocol for Bodo saltans , a free‐living kinetoplastid with tolerance to both marine and freshwater conditions and a close non‐parasitic relative of trypanosomatids. Our results show that...

Ocean chemistry is changing as a result of human activities. Atmospheric carbon dioxide (CO 2 ) concentrations are increasing, causing an increase in oceanic p CO 2 that drives a decrease in oceanic pH, a process called ocean acidification (OA). Higher CO 2 concentrations are also linked to rising global temperatures that can result in more stratified surface waters, reducing the exchange between surface and deep waters; this...

Coastal ecosystems are impacted by excessive nutrient inputs that cause degradation of water quality and impairments of ecosystem functioning. Regulatory and management efforts to enhance nutrient export from coastal ecosystems include sustainable oyster aquaculture that removes nitrogen in the form of oyster biomass and increases particulate export to underlying sediments where increased organic material may enhance microbial...

Summary The lithified oceanic crust, lower crust gabbros in particular, has remained largely unexplored by microbiologists. Recently, evidence for heterogeneously distributed viable and transcriptionally active autotrophic and heterotrophic microbial populations within low‐biomass communities was found down to 750 m below the seafloor at the Atlantis Bank Gabbro Massif, Indian Ocean. Here, we report on the diversity, activity...

Summary Diatom blooms are important features of productive marine ecosystems and are known to support higher trophic levels. However, when stressed or wounded, diatoms can produce oxylipin molecules known to inhibit the reproduction and development of copepods and decrease microzooplankton growth rates. Using oxylipin chemical treatments, lipidomic analysis and functional genomic approaches, we provide evidence that nitric oxi...

Mixotrophic oligotrich ciliates use plastids sequestered from algal prey to acquire energy and metabolic products from photosynthesis. We isolated mixotrophic oligotrichs from coastal waters off Massachusetts (MA) and California (CA), as well as from two freshwater ponds in MA, and identified associated plastid 23S rRNA genes. Ciliates were identified using a combination of microscopy and 18S rRNA phylogeny, and included Laboe...

Summary Studies on the microbial communities of deep subsurface sediments have indicated the presence of Bacteria and Archaea throughout the sediment column. Microbial eukaryotes could also be present in deep‐sea subsurface sediments; either bacterivorous protists or eukaryotes capable of assimilating buried organic carbon. DNA‐ and RNA‐based clone library analyses are used here to examine the microbial eukaryotic diversity an...