Active bicarbonate uptake in diatoms

Princeton University, Princeton, New Jersey, United States
Nature (Impact Factor: 41.46). 11/1997; 390(6657):243-244. DOI: 10.1038/36765
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    • "In most cases, there is entry of both CO 2 and HCO 3 – in CCMs (Korb et al., 1997; Tortell et al., 1997; Burkhardt et al., 2001; Giordano et al., 2005; Rost et al., 2006a,b, 2007; Tortell et al., 2008) and, in a few cases (see above) only CO 2 enters in algae with CCMs. Isolated, metabolically active chloroplasts of some green algae with CCMs show CO 2 and HCO 3 – uptake into the chloroplasts as well as into whole cells (Amoroso et al., 1998, van Hunnik et al., 2002, Giordano et al., 2005, and references therein). "
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    ABSTRACT: It is difficult to distinguish influx and efflux of inorganic C in photosynthesizing tissues; this article examines what is known and where there are gaps in knowledge. Irreversible decarboxylases produce CO2, and CO2 is the substrate/product of enzymes that act as carboxylases and decarboxylases. Some irreversible carboxylases use CO2; others use HCO3 (-). The relative role of permeation through the lipid bilayer versus movement through CO2-selective membrane proteins in the downhill, non-energized, movement of CO2 is not clear. Passive permeation explains most CO2 entry, including terrestrial and aquatic organisms with C3 physiology and biochemistry, terrestrial C4 plants and all crassulacean acid metabolism (CAM) plants, as well as being part of some mechanisms of HCO3 (-) use in CO2 concentrating mechanism (CCM) function, although further work is needed to test the mechanism in some cases. However, there is some evidence of active CO2 influx at the plasmalemma of algae. HCO3 (-) active influx at the plasmalemma underlies all cyanobacterial and some algal CCMs. HCO3 (-) can also enter some algal chloroplasts, probably as part of a CCM. The high intracellular CO2 and HCO3 (-) pools consequent upon CCMs result in leakage involving CO2, and occasionally HCO3 (-). Leakage from cyanobacterial and microalgal CCMs involves up to half, but sometimes more, of the gross inorganic C entering in the CCM; leakage from terrestrial C4 plants is lower in most environments. Little is known of leakage from other organisms with CCMs, though given the leakage better-examined organisms, leakage occurs and increases the energetic cost of net carbon assimilation.
    Journal of Experimental Botany 10/2015; DOI:10.1093/jxb/erv451 · 5.53 Impact Factor
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    • "During photosynthesis, organic carbon matter is formed from both HCO − 3 and CO 2 (aq) (Tortell et al., 1997) using both active and indirect transportation mechanisms (Sültemeyer et al., 1993) and C 3 and C 4 photosynthetic pathways (Reinfelder et al., 2000). Marine studies including those from the Bering Sea and North Pacific Ocean have demonstrated that the majority of diatom carbon originates from HCO − 3 via direct transportation (Tortell and Morel, 2002; Cassar et al., 2004; Martin and Tortell, 2006; Tortell et al., 2006, 2008). "
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    ABSTRACT: In comparison to other sectors of the marine system, the palaeoceanography of the subarctic North Pacific Ocean is poorly constrained. New diatom isotope records of δ13C, δ18O, δ30Si (δ13Cdiatom, δ18Odiatom, δ30Sidiatom), are presented alongside existing geochemical and isotope records to document changes in photic zone conditions, including nutrient supply and the efficiency of the soft-tissue biological pump, between Marine Isotope Stage (MIS) 4 and MIS 5e. Peaks in opal productivity in MIS 5b/c and MIS 5e are both associated with the breakdown of the regional halocline stratification and increased nutrient supply to the photic zone. Whereas the MIS 5e peak is associated with low rates of nutrient utilisation, the MIS 5b/c peak is associated with significantly higher rates of nutrient utilisation. Both peaks, together with other smaller increases in productivity in MIS 4 and 5a culminate with a~significant increase in freshwater input which strengthens/re-establishes the halocline and limits further upwelling of sub-surface waters to the photic zone. Whilst δ30Sidiatom and previously published records of diatom δ15N (δ15Ndiatom) (Brunelle et al., 2007, 2010) show similar trends until the latter half of MIS 5a, the records become anti-correlated after this juncture and into MIS 4, suggesting a possible change in photic zone state such as may occur with a shift to iron or silicon limitation.
    Climate of the Past 01/2015; 11(1):15-25. DOI:10.5194/cp-11-15-2015 · 3.38 Impact Factor
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    • "In addition, we do not consider this mechanism very likely, as most diatoms have been found to be able to Mar Ecol Prog Ser 273: 1–15, 2004 utilise HCO 3 – as carbon source in one way or another (e.g. Nimer et al. 1997, Tortell et al. 1997, Hobson et al. 2001). A third potential explanation for the effect of pH on DA production could be that pH-mediated changes in speciation of metals affect the production of DA due to increased toxicity or reduced bioavailability of the metal. "
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    ABSTRACT: The effect of elevated pH on growth and on production of the neurotoxin domoic acid was studied in selected diatoms belonging to the genera Pseudo-nitzschia and Nitzschia. Growth of most of the 11 species studied stopped at pH values of 8.7 to 9.1. However, for P. delicatissima and N. navis-varingica the pH limit for growth was higher, 9.3 and 9.7 to 9.8, respectively. A compilation of all available data on the pH limits for growth of marine planktonic diatoms suggests that species from ponds and rock pools all have higher limits than coastal and oceanic species. Taking only coastal and oceanic species into account, the data suggest that smaller species have a higher upper pH limit for growth than larger species. Elevated pH induced production of domoic acid in P, multiseries in amounts comparable to those detected previously under silicate and phosphate limitation. As Pseudo-nitzschia species are found in high concentrations in nutrient- enriched areas, high pH and hence induction of the production of domoic acid would be expected during blooms. These results may help to understand when and why Pseudo-nitzschia species produce domoic acid in the field.
    Marine Ecology Progress Series 06/2004; 273:1-15. DOI:10.3354/meps273001 · 2.62 Impact Factor
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