Chisholm
Sallie W.
Chisholm
Sallie W.
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DatasetProchlorococcus cell concentrations during the BiG-RAPA expedition (Cruise MV1015) in the Peru Current and Eastern South Pacific Subtropical Gyre between November and December of 2010(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2023-01-30) Berube, Paul ; Berta-Thompson, Jessica ; Coe, Allison ; Chisholm, Sallie W.These data include Prochlorococcus cell concentrations (total cell densities by flow cytometry and cell densities for specific ecotypes/clades determined by quantitative PCR). Samples were collected during the C-MORE Biogeochemical Gradients Role in Arranging Planktonic Assemblages (BiG-RAPA) expedition (Cruise MV1015) in the Peru Current and Eastern South Pacific Subtropical Gyre between dates 2010-11-19 and 2010-12-10 along a zonal transect from the northern coast of Chile to the island of Rapa Nui. Prochlorococcus is an important primary producer in the oligotrophic South Pacific Gyre and these data facilitate studies examining Prochlorococcus' ecology. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/886299
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ArticlePhosphonate production by marine microbes: exploring new sources and potential function(National Academy of Sciences, 2022-03-07) Acker, Marianne ; Hogle, Shane L. ; Berube, Paul M. ; Hackl, Thomas ; Coe, Allison ; Stepanauskas, Ramunas ; Chisholm, Sallie W. ; Repeta, Daniel J.Phosphonates are organophosphorus metabolites with a characteristic C-P bond. They are ubiquitous in the marine environment, their degradation broadly supports ecosystem productivity, and they are key components of the marine phosphorus (P) cycle. However, the microbial producers that sustain the large oceanic inventory of phosphonates as well as the physiological and ecological roles of phosphonates are enigmatic. Here, we show that phosphonate synthesis genes are rare but widely distributed among diverse bacteria and archaea, including Prochlorococcus and SAR11, the two major groups of bacteria in the ocean. In addition, we show that Prochlorococcus can allocate over 40% of its total cellular P-quota toward phosphonate production. However, we find no evidence that Prochlorococcus uses phosphonates for surplus P storage, and nearly all producer genomes lack the genes necessary to degrade and assimilate phosphonates. Instead, we postulate that phosphonates are associated with cell-surface glycoproteins, suggesting that phosphonates mediate ecological interactions between the cell and its surrounding environment. Our findings indicate that the oligotrophic surface ocean phosphonate pool is sustained by a relatively small fraction of the bacterioplankton cells allocating a significant portion of their P quotas toward secondary metabolism and away from growth and reproduction.
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ArticleProchlorococcus extracellular vesicles: molecular composition and adsorption to diverse microbes(Society for Applied Microbiology, 2021-11-12) Biller, Steven J. ; Lundeen, Rachel A. ; Hmelo, Laura R. ; Becker, Kevin W. ; Arellano, Aldo A. ; Dooley, Keven ; Heal, Katherine R. ; Carlson, Laura Truxal ; Van Mooy, Benjamin A. S. ; Ingalls, Anitra ; Chisholm, Sallie W.Extracellular vesicles are small (~50–200 nm diameter) membrane-bound structures released by cells from all domains of life. While vesicles are abundant in the oceans, their functions, both for cells themselves and the emergent ecosystem, remain a mystery. To better characterize these particles – a prerequisite for determining function – we analysed the lipid, protein, and metabolite content of vesicles produced by the marine cyanobacterium Prochlorococcus. We show that Prochlorococcus exports a diverse array of cellular compounds into the surrounding seawater enclosed within discrete vesicles. Vesicles produced by two different strains contain some materials in common, but also display numerous strain-specific differences, reflecting functional complexity within vesicle populations. The vesicles contain active enzymes, indicating that they can mediate extracellular biogeochemical reactions in the ocean. We further demonstrate that vesicles from Prochlorococcus and other bacteria associate with diverse microbes including the most abundant marine bacterium, Pelagibacter. Together, our data point toward hypotheses concerning the functional roles of vesicles in marine ecosystems including, but not limited to, possibly mediating energy and nutrient transfers, catalysing extracellular biochemical reactions, and mitigating toxicity of reactive oxygen species.
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ArticleChitin utilization by marine picocyanobacteria and the evolution of a planktonic lifestyle(National Academy of Sciences, 2023-05-16) Capovilla, Giovanna ; Braakman, Rogier ; Fournier, Gregory P. ; Hackl, Thomas ; Schwartzman, Julia ; Lu, Xinda ; Yelton, Alexis ; Longnecker, Krista ; Soule, Melissa C. Kido ; Thomas, Elaina ; Swarr, Gretchen ; Mongera, Alessandro ; Payette, Jack G. ; Castro, Kurt G. ; Waldbauer, Jacob R. ; Kujawinski, Elizabeth B. ; Cordero, Otto X. ; Chisholm, Sallie W.Marine picocyanobacteria Prochlorococcus and Synechococcus, the most abundant photosynthetic cells in the oceans, are generally thought to have a primarily single-celled and free-living lifestyle. However, while studying the ability of picocyanobacteria to supplement photosynthetic carbon fixation with the use of exogenous organic carbon, we found the widespread occurrence of genes for breaking down chitin, an abundant source of organic carbon that exists primarily as particles. We show that cells that encode a chitin degradation pathway display chitin degradation activity, attach to chitin particles, and show enhanced growth under low light conditions when exposed to chitosan, a partially deacetylated soluble form of chitin. Marine chitin is largely derived from arthropods, which underwent major diversifications 520 to 535 Mya, close to when marine picocyanobacteria are inferred to have appeared in the ocean. Phylogenetic analyses confirm that the chitin utilization trait was acquired at the root of marine picocyanobacteria. Together this leads us to postulate that attachment to chitin particles allowed benthic cyanobacteria to emulate their mat-based lifestyle in the water column, initiating their expansion into the open ocean, seeding the rise of modern marine ecosystems. Subsequently, transitioning to a constitutive planktonic life without chitin associations led to cellular and genomic streamlining along a major early branch within Prochlorococcus. Our work highlights how the emergence of associations between organisms from different trophic levels, and their coevolution, creates opportunities for colonizing new environments. In this view, the rise of ecological complexity and the expansion of the biosphere are deeply intertwined processes.