R. Turk results 23
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Temperature‐dependent growth and activity in a globally distributed nitrogen‐fixing haptophyteNARA Subscribed
Dinitrogen (N 2 )‐fixing microorganisms play a crucial role in supplying nitrogen (N) to the oceans by converting atmospheric N 2 into bioavailable N. N 2 fixation was thought to be limited to warm oligotrophic ocean waters, but the association between the N 2 ‐fixing UCYN‐A cyanobacterium and specific haptophytes, including Braarudosphaera bigelowii and relatives, has been found in diverse ocean environments, including warm s...
Machine Learning–Based Identification of Target Groups for Thrombectomy in Acute StrokeNARA Subscribed
Whether endovascular thrombectomy (EVT) improves functional outcome in patients with large-vessel occlusion (LVO) stroke that do not comply with inclusion criteria of randomized controlled trials (RCTs) but that are considered for EVT in clinical practice is uncertain. We aimed to systematically identify patients with LVO stroke underrepresented in RCTs who might benefit from EVT. Following the premises that (i) patients witho...
Dinitrogen (N 2 ) fixation is carried out by specialized microbes, called diazotrophs, and is a major source of nitrogen supporting primary production in oligotrophic oceans. One of the best-characterized diazotroph habitats is the North Pacific Subtropical Gyre (NPSG), where warm, chronically N-limited surface waters promote year-round N 2 fixation. At Station ALOHA (A Long-Term Oligotrophic Habitat Assessment) in the NPSG, N...
Light and depth dependency of nitrogen fixation by the non‐photosynthetic, symbiotic cyanobacterium UCYN‐ANARA Subscribed
Summary The symbiotic cyanobacterium UCYN‐A is one of the most globally abundant marine dinitrogen (N 2 )‐fixers, but cultures have not been available and its biology and ecology are poorly understood. We used cultivation‐independent approaches to investigate how UCYN‐A single‐cell N 2 fixation rates (NFRs) and nifH gene expression vary as a function of depth and photoperiod. Twelve‐hour day/night incubations showed that UCYN‐...
Latitudinal constraints on the abundance and activity of the cyanobacterium UCYN‐A and other marine diazotrophs in the North PacificNARA Subscribed
The number of marine environments known to harbor dinitrogen (N 2 )‐fixing (diazotrophic) microorganisms is increasing, prompting a reassessment of the biogeography of marine diazotrophs and N 2 fixation rates (NFRs). Here, we investigate the diversity, abundance, and activity of diazotrophic microorganisms in the North Pacific Subtropical Gyre (NPSG), a diazotrophic habitat, and the North Pacific Transition Zone (NPTZ), a reg...
Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific OceanNARA Subscribed
Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world's oceans. Differential preferences for specific N substrates may be important in controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate ( ), ammo...
Rates of dinitrogen fixation and the abundance of diazotrophs in North American coastal waters between Cape Hatteras and Georges BankNARA Subscribed
We coupled dinitrogen (N 2 ) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid‐Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N 2 fixation were as high as 49.8 nmol N L −1 d −1 and areal rates as high as 837.9 µmol N m −2 d −1 in our study area. Our results suggest that N...
Dimethyl sulphide and methanethiol formation in microbial mats: potential pathways for biogenic signaturesNARA Subscribed
Summary Mechanisms of dimethyl sulphide (DMS) and methanethiol (MT) production and consumption were determined in moderately hypersaline mats, Guerrero Negro, Mexico. Biological pathways regulated the net flux of DMS and MT as revealed by increases in flux resulting from decreased salinity, increased temperature and the removal of oxygen. Dimethylsulphoniopropionate (DMSP) was not present in these microbial mats and DMS and MT...
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