Students interested in joining my lab for graduate studies can apply to the MIT-WHOI Joint Program in Oceanography. I encourage all prospective students to seek independent funding, such as the NSF Graduate Research Fellowship Program.
Undergraduate Summer Student Research
Undergraduates interested in conducting summer research projects at WHOI can apply to the WHOI Summer Student Fellowship Program or the Woods Hole Partnership Educational Program.
Past Summer Student Fellows
Project Abstract: Mesodinium rubrum is a marine photosynthetic ciliate that is observed globally in neritic and estuarine habitats and is known to sequester plastids, mitochondria, and nuclei from cryptophyte algae. Using psychrophilic strains of M. rubrum and their prey Geminigera cryophilia isolated from McMurdo Sound, Antarctica, we measured protein expression, pigment content, and quantum efficiency of PSII (Fv/Fm) of steady-state cultures grown at 10 and 20 µE m-2 s-1. Additionally, we measured the Fv/Fm of stressed cultures acclimated to <10 and 20 µE m-2 s-1 then transferred to highlight (HL) conditions (~90-120 µE m-2 s-1) at 0 h, 18 h, 42 h, and 66 h. When grown at 20µE m-2 s-1, M. rubrum displayed a 2-fold increase in expression of PSII proteins (LHCI, and PsbA) when compared to G. cryophila. While this was the case for PS II proteins, there was no difference in the levels of PS I protein (PsaC) expressed at either light level. However, M. rubrum showed a dramatic, 6 fold increase in the expression of RbcL at both light levels when compared to G. cryophila grown under the same conditions. Differential protein expression suggests that M. rubrum is affected by small increases in light levels and may be increasing production of PS II reaction complexes as a photoacclimation mechanism, while increasing the expression of RbcL to offset the inefficiency of RUBISCO at low temperatures. These results indicate that M. rubrum exhibits a high level of control over sequestered plastids. Both M. rubrum and G. cryophila cells transferred from <10 µE m-2 s-1 to HL showed an rapid decline in Fv/Fm from 0 to 42h, then an increase in Fv/Fm at 66h. M. rubrum and G. cryophila cells transferred from 20 µE m-2 s-1 to HL showed fluctuations in Fv/Fm, first increasing at 18 h, then decreasing to low levels at 42h, and then finally recovering to baseline, steady state levels by 66h. These results indicate that by 66h, the cells may have begun to photoacclimate to HL conditions, and have begun to recover PSII health, further supporting the ability of M. rubrum to utilize and regulate acquired plastids.
Project Abstract: Warm water, reef building coral and their photosynthetic endosymbiont, Symbiodinium spp., exist in a unique relationship that presents each partner with distinct stresses not faced by individual marine organisms. Primary examples of this are the dramatic coral bleaching events witnessed in the last several decades correlated with increases in ocean temperature, whereby corals expel their symbionts, potentially leading to fatality of the host and destruction of coral habitat. Although the molecular mechanism leading to these breakdowns of communication are not well understood, work thus far has highlighted oxidative stress as a distinct characteristic of the stress response in both the symbiont and its host. The present study sought specifically to characterize the role of reactive oxygen species (ROS) and nitric oxide (NO), a well-conserved signaling and oxidative molecule common to life of all levels of complexity, in modulating the responses of Symbiodinium spp. to acute and long term heat stress. Here we show a functional role for NO in the sensitization and ultimate destruction of the alga in response to heat stress, while undermining the idea that ROS themselves can act as functional molecules to initiate metabolic dysfunction and death. Furthermore, differences between genetically similar heat-sensitive and heat-tolerant strains’ responses to the loss or gain of NO in the presence of heat-stress and under normal conditions points to possible differences in regulation of intracellular NO, which may be an underlying cause for their different phenotypes.
Zaitsev, E and MD Johnson (2011) Investigating the role of nitric oxide, oxidative stress, and temperature in Symbiodinium spp. ASLO, San Juan, PR