Iron and Prochlorococcus
Thompson, Anne Williford
MetadataShow full item record
KeywordPhotosynthesis; Iron; Metabolism; Knorr (Ship : 1970-) Cruise KN182-5; Knorr (Ship : 1970-) Cruise KN182-9
Iron availability and primary productivity in the oceans are intricately linked through photosynthesis. At the global scale we understand how iron addition induces phytoplankton blooms through meso-scale iron-addition experiments. At the atomic scale, we can describe the length and type of bonds that connect iron atoms to components of photosystem I, the most efficient light-harvesting complex in nature. Yet, we know little of how iron influences microbial diversity and distribution in the open ocean. In this study, we assess the influence of iron on the ecology of the numerically abundant marine cyanobacterium, Prochlorococcus. With its minimal genome and ubiquity in the global ocean, Prochlorococcus represents a model system in which to study the dynamics of the link between iron and primary productivity. To this end, we tested the iron physiology of two closely-related Prochlorococcus ecotypes. MED4 is adapted to high-light environments while MIT9313 lives best in low-light conditions. We determined that MIT9313 is capable of surviving at low iron concentrations that completely inhibit MED4. Furthermore, concentrations of Fe’ that inhibit growth in culture are sufficient to support Prochlorococcus growth in the field, which raises questions about the species of iron available to Prochlorococcus. We then examined the molecular basis for the ability of MIT9313 to grow at lower iron concentrations than MED4 by assessing whole-genome transcription in response to changes in iron availability in the two ecotypes. Genes that were differentially expressed fell into two categories: those that are shared by all (Prochlorococcus core genome) and those that are not (non-core genome). Only three genes shared between MED4 and MIT9313 were iron-responsive in both strains. We then tested the iron physiology of picocyanobacteria in the field and found that Synechococcus is iron-stressed in samples where Prochlorococcus is not. Finally, we propose a method to measure how iron stress in Prochlorococcus changes over natural gradients of iron in the oligotrophic ocean by quantifying transcription of the iron-stress induced gene, isiB. Taken together, our studies demonstrate that iron metabolism influences the ecology of Prochlorococcus both by contributing to its diversity and distinguishing it from other marine cyanobacteria.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2009
Showing items related by title, author, creator and subject.
Acoustic and oceanographic observations and configuration information for the WHOI moorings from the SW06 experiment Newhall, Arthur E.; Duda, Timothy F.; von der Heydt, Keith; Irish, James D.; Kemp, John N.; Lerner, Steven A.; Liberatore, Stephen P.; Lin, Ying-Tsong; Lynch, James F.; Maffei, Andrew R.; Morozov, Andrey K.; Shmelev, Alexey A.; Sellers, Cynthia J.; Witzell, Warren E. (Woods Hole Oceanographic Institution, 2007-05)This document describes data, sensors, and other useful information pertaining to the moorings that were deployed from the R/V Knorr from July 24th to August 4th, 2006 in support of the SW06 experiment. The SW06 experiment ...
The ecology of colonial radiolarians : their colony morphology, trophic interactions and associations, behavior, distribution, and the photosynthesis of their symbionts Swanberg, Neil Ralph (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1979-08)Colonial radiolarians (Spumellaria) are among the most common and abundant large zooplankton, but they have been little studied by modern biologists. Colonies were found on 98% of epipelagic diving stations in the period ...
Cheney, Jerry (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1982-08)Zooplankton samples were collected with the MOCNESS (Multiple Opening/ Closing Net and Environmental Sensing System) on six cruises in the western North Atlantic Ocean during the period from August 1975 to November 1977 ...