Exopolymer production as a function of cell permeability and death in a diatom (Thalassiosira weissflogii) and a cyanobacterium (Synechococcus elongatus)

Abstract

Exopolymer particles are found throughout the ocean and play a significant biogeochemical role in carbon cycling. Transparent exopolymer particles (TEP) are composed of acid polysaccharides, and Coomassie staining particles (CSP) are proteins. TEPs have been extensively studied in the ocean, while CSP have been largely overlooked. The objective of this research was to determine the role of stress and cell permeability in the formation of TEP and CSP. The diatom Thalassiosira weissflogii and cyanobacterium Synechococcus elongatus were grown in batch cultures and exposed to hydrogen peroxide (0, 10, and 100 μM) as an environmental stressor. There was no correlation between TEP and CSP concentrations, indicating that they are different populations of particles rather than different chemical components of the same particles. CSP concentrations were not affected by hydrogen peroxide concentration and did not correlate with indicators of stress and cell death. In contrast, TEP concentrations in both taxa were correlated with a decrease in the effective quantum yield of photosystem II, increased activity of caspase-like enzymes, and an increase in the proportion of the population with permeable cell membranes, indicating that TEP production was associated with the process of cell death. These data show that different environmental factors and physiological processes affected the production of TEP and CSP by phytoplankton. TEP and CSP are separate populations of exopolymer particles with potentially different biogeochemical roles in the ocean.

Dynamics of transparent exopolymer particle production and aggregation during viral infection of the coccolithophore, Emiliania huxleyi

“…This suggests that, in the absence of EhV207 infection, E. huxleyi-derived metabolites other than TEP contributed towards aggregation. Proteinaceous CSPs, can also facilitate the formation of aggregates and 'marine snow' (Long and Azam, 1996;Cisternas-Novoa et al, 2015;Thornton and Chen, 2017). Quantification of the average blue to average red ratio (blue:red) of large aggregates ( Fig.…”

Multicellular Features of Phytoplankton

“…Recently, proteins were characterized as an additional structural component involved in phytoplankton aggregation (Thornton and Chen, 2017). Interestingly, TEP generation increases under stress conditions, however production of matrix proteins does not (Thornton and Chen, 2017). These observations suggest that the production of the two polymers is differentially regulated, demonstrating the insufficiently studied complexity of phytoplankton aggregates.…”

“…The algal aggregates are held together by at least two structural components: extracellular DNA (Figure 2) and Transparent Exopolymer Particles (TEP) (Figure 2). Recently, proteins were characterized as an additional structural component involved in phytoplankton aggregation (Thornton and Chen, 2017). Interestingly, TEP generation increases under stress conditions, however production of matrix proteins does not (Thornton and Chen, 2017).…”

Coomassie Stainable Particles (CSP): Protein Containing Exopolymer Particles in the Ocean

“…Numerical data were obtained directly from papers and supplementary material, or indirectly from figures that were analyzed using inverse graphing software (Engauge Digitizer 10.3). Data from the Thornton lab (Thornton et al, 2016;Thornton and Chen, 2017) were obtained from original spreadsheets. Most data were individual data points, though in some cases means and standard deviations were obtained.…”

“…Manipulative experiments have been used as a tool to determine what factors affect CSP production. These experiments fall into two categories; manipulative experiments using natural biological communities grown under approximations of in situ conditions in micro-or mesocosms (Prieto et al, 2002;Radić et al, 2006;Galgani et al, 2014;Engel et al, 2015a), and laboratory experiments with defined cultures of microorganisms (Bhaskar et al, 2005;Grossart et al, 2006;Endres et al, 2013;Galgani and Engel, 2013b;Thornton, 2014;Thornton and Chen, 2017). Experiments in micro-and mesocosms have been simulations of different ocean acidification conditions (Galgani et al, 2014) or manipulations of nutrient ratios and availability (Radić et al, 2006;Engel et al, 2015a).…”