Elemental composition of single cells of various strains of marine Prochlorococcus and Synechococcus using X‐ray microanalysis

Abstract

We measured the elemental composition of single cells from six strains of marine Prochlorococcus and two strains of marine Synechococcus by X-ray microanalysis in the transmission electron microscope (TEM), which allows measurements of all major elements in cells without any fixation or staining. . Elemental composition varied widely in relation to strains and growth media. However, C : P and N : P ratios were above the Redfield ratio in all Prochlorococcus strains and one of the Synechococcus strains (WH 8103). This likely reflected the low P content of these cells. This low P requirement would be clearly advantageous in the oligotrophic conditions occupied by these organisms. The high relative carbon content, compared to what has been found for heterotrophic bacteria using similar methods, is suggested to confer a competitive advantage to photosynthetic over heterotrophic bacteria in ecosystems where both functional groups are mineral nutrient limited.

Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation

“…Using the flowcytometer we could not detect these changes. The findings on the variations in N and P quota are in agreement with the observations that the cellular composition of pico-phytoplankton is subject to substantial change, for instance due to changes in the physico-chemical environment (Bertilsson et al, 2003;Heldal et al, 2003;Veldhuis et al, 2005). However, the absolute values that we report were higher than reported in other studies.…”

“…The N and P quota in Synechococcus ranged from 1.4-1.5 Â 10 À15 mol N cell À1 and 0.06-0.11 Â 10 À15 mol P cell À1 under nutrient-replete conditions to 1.5-2.9 Â 10 À15 mol N cell À1 and 0.02-0.03 Â 10 À15 mol P cell À1 under P-limited conditions (Table 3). Similarly low N and P quota were measured in two strains of Synechococcus (Heldal et al, 2003) (Table 3). These values are typically one to two orders of magnitude lower than those reported in our study.…”

“…Two prokaryotic cyanobacteria, Prochlorococcus marinus (Chisholm et al, 1988;Partensky et al, 1999) and Synechococcus spp. (Waterbury et al, 1979(Waterbury et al, , 1986Olson et al, 1990;Li, 1998;Bertilsson et al, 2003;Heldal et al, 2003) belong to the most thoroughly investigated algal species of the pico-phytoplankton community. Only a very limited number of eukaryotic pico-phytoplankton species have been investigated in detail.…”

Cell surface acid-base properties of the cyanobacterium Synechococcus : Influences of nitrogen source, growth phase and N:P ratios

“…Relatively small differences in nutrient utilization or regional adaptation in cyanobacteria translates into biochemical responses that are reflected in variations in elemental composition of the cells. P quotas for marine cyanobacteria have been reported to vary over approximately an order of magnitude (e.g., 22-116 amol/cell; Heldal et al, 2003;Twining et al, 2010), consistent with the suggestion that cyanobacteria possess radical surface modification mechanisms to cope with nutrient limitation, such as replacement of surface phospholipids with sulfolipids (Van Mooy et al, 2006). In our study, we observed a decreased role for protein in cell surface reactivity, and increased role for carbohydrates and lipids, as media N:P ratios departed from the reference condition of 14.5.…”

Transport functions dominate the SAR11 metaproteome at low-nutrient extremes in the Sargasso Sea

“…In the Sargasso Sea, Prochlorococcus cell numbers peak during the summer at depths between 80 and 200 m, whereas Synechococcus cells reach their maximum density during spring blooms in surface waters. Synechococcus cells are slightly larger (0.62-1.56 mm 3 compared to 0.077-0.22 mm 3 for Prochlorococcus (Heldal et al, 2003)), and thus account for a higher proportion of primary producer biomass than cell numbers would suggest.…”