Kimberly Halsey

Phytoplankton Physiological Ecology

Category: Publications

Moore et al. 2017 published in PLoS One

Our newest lab paper was published today. This manuscript describes two important discoveries in diatom lifecycles.

PLoS ONE 12(7): e0181098. https://doi.org/10.1371/journal.pone.0181098

1.) Thalassiosira pseudonana IS a sexual diatom species

2.) Ammonium induces sex in T. pseudonana and at least two other centric diatoms.

To prove these discoveries, Eric Moore with help from Briana Bullington carried out a number of carefully controlled culturing experiments, imaged all of the cell morphologies in the lifecycle, and identified >1,200 genes that were differentially expressed under conditions of ammonium induced cell differentiation. Some of these genes are involved in meiosis, flagellar synthesis, and sex differentiation.

Thanks to all of our co-authors, Alex Weisberg, Jeff Chang, and Yuan Jiang for their help with gene expression analysis and statistical testing.

Diatom sex

Nobody had ever seen the model centric diatom, Thalassiosira pseudonana, undergo sexual reproduction. Grad student, Eric Moore, documented the sexual stages and showed upregulation of genes involved in meiosis and flagellar synthesis. Moreover, he figured out what triggers these diatoms and other centric diatoms to shift into the sexual cycle resulting in cell enlargement. Read about it here on BioRxiv.

doi: https://doi.org/10.1101/144667

Plankton actively cycle volatile organic carbon

Our most recent paper on VOC cycling in the surface ocean was just published in Limnology and Oceanography. Phytoplankton produce different profiles of VOCs depending on species and some bacterioplankton, including the ubiquitous and abundant SAR11 bacteria consume these compounds. We designed new incubation chambers and attached these chambers to a PTR-MS to make real time measurements of VOC production and consumption . This work was a collaborative effort with atmospheric physicists at NOAA. Halsey et al. 2017 doi: 10.1002/lno.10596

New paper on light limitation

Our newest paper on photosynthetic energy use was accepted yesterday in Photosynthesis Research. Former graduate student Nerissa Fisher (MS 2015) discovered that under very low light availability, diatoms shift their metabolism in favor of very short ATP generating pathways that circumvent carbon intermediates. These results suggest that this type of pathway gating facilitates the remarkably high efficiencies with which diatoms convert light energy into biomass, especially in low light (Fisher and Halsey, 2016). The paper can be found here:

Mechanisms that increase the growth efficiency of diatoms in low light

New paper on VOC production by SAR11

A new paper from the Giovannoni lab was published this week in Nature Microbiology on the unexpected discovery that SAR11 bacteria produce methane thiol and DMS from DMSP metabolism. Our role on this paper was to  measure real time production of these compounds using PTR-MS. Overall, the research described in this paper combined culturing, biochemistry, genomics, proteomics, and atmospheric chemistry to reveal the remarkable activities of this tiny, abundant, and remarkably impactful bacterium.

Sun et al. 2016_Nat_Microbiol.

 

Halsey and Jones, 2015

ARMS fig 1Our 2015 paper, Phytoplankton Strategies for Photosynthetic Energy Allocation in Annual Review of Marine Science.

 

© 2017 Kimberly Halsey

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