PROGRAMMED-CELL-DEATH

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Trichodesmium trichome showing DNA stained in blue

Programmed cell death (PCD) is an irreversible, genetically controlled form of cell suicide that is essential to promote and maintain genetic stability and is critical for the regulation of cellular and tissue homeostasis in metazoans. PCD has been observed in a variety of unicellular organisms including prokaryotic bloom-forming cyanobacteria, chlorophytes, dinoflagellates, diatoms, and coccolithophores. Trichodesmium also displays autocatalytic PCD in response to stressors such as oxidation, high irradiance, and Fe-depletion.
In the oceans Trichodesmium forms extensive blooms in nutrient-poor tropical and subtropical regions. These massive blooms generally collapse several days after forming, but the cellular mechanism responsible along with the magnitude of associated C and N export, are as yet unknown. Our work from laboratory simulations demonstrate that extremely rapid development and abrupt, PCD-induced demise (within 2-3 d) of Trichodesmium blooms lead to greatly elevated excretions of transparent exopolymers and a massive downward pulse of particulate organic matter. Our results mechanistically link autocatalytic PCD and bloom collapse to quantitative C and N export fluxes and suggest that PCD may impact biological pump efficiency in the oceans.

Past Students

Past students and Post doctoral Fellows

–       Liel Magnezi, Msc 2018, Trichodesmium bloom formation

–       Dan Miller, PhD 2018, Assessing the physiological and compositional                                               response of coastal microbial populations to increased pCO2 and to                                eutrophication

–        Natasha Belkin, PhD 2016, Impacts of seawater desalination discharges on                   coastal bacterial and phytoplanktonic communities

–        Reut Sorek Abramovich, PhD. Post-doc fellow, 2015 Toxins in Trichodesmium- —

–        Adi Levi, PhD 2015, Applying innovative nano-technology approaches to                       reduce biofilm development on membrane and surfaces in the desalination                     industry

–        Eyal Rahav, PhD 2013, Controls on dinitrogen fixation in the eastern                                                                             Mediterranean

–        Edo Bar Zeev, PhD 2012, TEP and biofilm formation

                                    MSc 2007, Nitrogen fixation in aquatic symbiotic associations

–        Itamar Avishai, MSc 2012, Programmed cell death in Trichodesmium

–        Sara Ohaion, MSc 2012, Molecular diagnostics of controls on N2 fixation

–        Ben Brinberg, MSc 2013, Microbial ecology of subterranean estuaries of                         Mediterranean coastline

–        Tali Yogev, PhD 2009, Nitrogen fixation in the eastern Mediterranean

–        Orly Levitan, PhD 2010, Impacts of CO2 on aquatic dinitrogen fixation

                                 MSc 2005, Influence of CO2 on aquatic nitrogen fixation

 –       Eric Ben David, Post-doc fellow 2010, Programmed cell death in Trichodesmium

–        Tamar Bsor-Rachamim, PhD 2010, Nutrient recycling by zooplankton in                        Lake  Kinneret

–        Max Rubin, MSc 2009, Fe uptake in Trichodesmium

–        Sammy Frenk, MSc 2008, Ammonium supply for optimal growth of juvenile                    and mature thalli of Porphyra rosengurtii (Rhodophyta)

–        Gad Rosenberg, MSc 2007, Programmed cell death in Trichodesmium

–        Dovi Kelman, Post-doc fellow 2007, Natural products from Trichodesmium

–        Chen Sherman, MSc 2006, Effect of varying pH on Trichodesmium