Constraining the oxygen requirements for modern microbial eukaryote diversity.

Eukaryotes originated prior to the establishment of modern marine oxygen (O) levels. According to the body fossil and lipid biomarker records, modern (crown) microbial eukaryote lineages began diversifying in the ocean no later than ~800 Ma. While it has long been predicted that increasing atmospheric O levels facilitated the early diversification of microbial eukaryotes, the O levels needed to permit this diversification remain unconstrained.

Testate amoebae (Arcellinida, Amoebozoa) community diversity in New England bogs and fens assessed through lineage-specific amplicon sequencing.

Testate amoebae (order Arcellinida) are abundant in freshwater ecosystems, including low pH bogs and fens. Within these environments, Arcellinida are considered top predators in microbial food webs and their tests are useful bioindicators of paleoclimatic changes and anthropogenic pollutants. Accurate species identifications and characterizations of diversity are important for studies of paleoclimate, microbial ecology, and environmental change; however, morphological species definitions mask cryptic diversity, which is a common phenomenon among microbial eukaryotes.

Single-cell transcriptomics supports presence of cryptic species and reveals low levels of population genetic diversity in two testate amoebae morphospecies with large population sizes.

The enormous population sizes and wide biogeographical distribution of many microbial eukaryotes set the expectation of high levels of intraspecific genetic variation. However, studies investigating protist populations remain scarce, mostly due to limited 'omics data. Instead, most genetics studies of microeukaryotes have thus far relied on single loci, which can be misleading and do not easily allow for detection of recombination, a hallmark of sexual reproduction.

Parasitic infections by Group II Syndiniales target selected dinoflagellate host populations within diverse protist assemblages in a model coastal pond.

Protists are integral to marine food webs and biogeochemical cycles; however, there is a paucity of data describing specific ecological niches for some of the most abundant taxa in marker gene libraries. Syndiniales are one such group, often representing the majority of sequence reads recovered from picoplankton samples across the global ocean. However, the prevalence and impacts of syndinian parasitism in marine environments remain unclear.

Environmental factors shaping bacterial, archaeal and fungal community structure in hydrothermal sediments of Guaymas Basin, Gulf of California.

The flanking regions of Guaymas Basin, a young marginal rift basin located in the Gulf of California, are covered with thick sediment layers that are hydrothermally altered due to magmatic intrusions. To explore environmental controls on microbial community structure in this complex environment, we analyzed site- and depth-related patterns of microbial community composition (bacteria, archaea, and fungi) in hydrothermally influenced sediments with different thermal conditions, geochemical regimes, and extent of microbial mats. We compared communities in hot hydrothermal sediments (75-100°C at ~40 cm depth) covered by orange-pigmented Beggiatoaceae mats in the Cathedral Hill area, temperate sediments (25-30°C at ~40 cm depth) covered by yellow sulfur precipitates and filamentous sulfur oxidizers at the Aceto Balsamico location, hot sediments (>115°C at ~40 cm depth) with orange-pigmented mats surrounded by yellow and white mats at the Marker 14 location, and background, non-hydrothermal sediments (3.

Meta-omics highlights the diversity, activity and adaptations of fungi in deep oceanic crust.

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 and adaptations of fungal communities in the deep oceanic crust from ~10 to 780 mbsf by combining metabarcoding analyses with mid/high-throughput culturing approaches.

Microbial Community Structure and Associations During a Marine Dinoflagellate Bloom.

Interactions between microorganisms and algae during bloom events significantly impacts their physiology, alters ambient chemistry, and shapes ecosystem diversity. The potential role these interactions have in bloom development and decline are also of particular interest given the ecosystem impacts of algal blooms. We hypothesized that microbial community structure and succession is linked to specific bloom stages, and reflects complex interactions among taxa comprising the phycosphere environment.

Insights into the loss factors of phytoplankton blooms: The role of cell mortality in the decline of two inshore blooms.

While considerable effort has been devoted to understanding the factors regulating the development of phytoplankton blooms, the mechanisms leading to bloom decline and termination have received less attention. Grazing and sedimentation have been invoked as the main routes for the loss of phytoplankton biomass, and more recently, viral lysis, parasitism and programmed cell death (PCD) have been recognized as additional removal factors. Despite the importance of bloom declines to phytoplankton dynamics, the incidence and significance of various loss factors in regulating phytoplankton populations have not been widely characterized in natural blooms.

LSU rDNA based RFLP assays for the routine identification of Gambierdiscus species.

The Gambierdiscus genus is a group of benthic dinoflagellates commonly associated with ciguatera fish poisoning (CFP), which is generally found in tropical or sub-tropical regions around the world. Morphologically similar species within the genus can vary in toxicity; however, species identifications are difficult or sometimes impossible using light microscopy. DNA sequencing of ribosomal RNA genes (rDNA) is thus often used to identify and describe Gambierdiscus species and ribotypes, but the expense and time can be prohibitive for routine culture screening and/or large-scale monitoring programs.

Rapid growth and concerted sexual transitions by a bloom of the harmful dinoflagellate (Dinophyceae).

Transitions between life cycle stages by the harmful dinoflagellate are critical for the initiation and termination of its blooms. To quantify these transitions in a single population, an Imaging FlowCytobot (IFCB), was deployed in Salt Pond (Eastham, Massachusetts), a small, tidally flushed kettle pond that hosts near annual, localized blooms. Machine-based image classifiers differentiating life cycle stages were developed and results were compared to manually corrected IFCB samples, manual microscopy-based estimates of abundance, previously published data describing prevalence of the parasite , and a continuous culture of infected with .

CHARACTERIZATION OF 17 NEW MICROSATELLITE MARKERS FOR THE DINOFLAGELLATE (DINOPHYCEAE), A HARMFUL ALGAL BLOOM SPECIES.

is the toxic marine dinoflagellate responsible for "red tide" events in temperate and sub-arctic waters worldwide. In the Gulf of Maine (GOM) and Bay of Fundy in the Northwest Atlantic, blooms of recur annually, and are associated with major health and ecosystem impacts. In this region, microsatellite markers have been used to investigate genetic structure and gene flow; however, the loci currently available for this species were isolated from populations from Japan and the North Sea, and only a subset are suitable for the analysis of populations in the Northwest Atlantic.