In Synechococcus sp. competition for energy between assimilation and acquisition of C and those of N only occurs when growth is light limited

Zuoxi Ruan, John A. Raven, Mario Giordano (Lead / Corresponding author)

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The carbon-concentrating mechanisms (CCMs) of cyanobacteria counteract the low CO2 affinity and CO2:O2 selectivities of the Rubisco of these photolithotrophs and the relatively low oceanic CO2 availability. CCMs have a significant energy cost; if light is limiting, the use of N sources whose assimilation demands less energy could permit a greater investment of energy into CCMs and inorganic C (Ci) assimilation. To test this, we cultured Synechococcus sp. UTEX LB 2380 under either N or energy limitation, in the presence of NO3- or NH4+. When growth was energy-limited, NH4+-grown cells had a 1.2-fold higher growth rate, 1.3-fold higher dissolved inorganic carbon (DIC)-saturated photosynthetic rate, 19% higher linear electron transfer, 80% higher photosynthetic 1/K1/2(DIC), 2.0-fold greater slope of the linear part of the photosynthesis versus DIC curve, 3.5-fold larger intracellular Ci pool, and 2.3-fold higher Zn quota than NO3--grown cells. When energy was not limiting growth, there were not differences between NH4+- and NO3--grown cells, except for higher linear electron transfer and larger intracellular Ci pool.We conclude that, when energy limits growth, cells that use the cheaper N source divert energy from N assimilation to C acquisition and assimilation; this does not happen when energy is not limiting.

Original languageEnglish
Pages (from-to)3829-3839
Number of pages11
JournalJournal of Experimental Botany
Volume68
Issue number14
Early online date28 Mar 2017
DOIs
Publication statusPublished - 1 Jun 2017

Keywords

  • Ammonium
  • CO2 concentrating mechanisms (CCMs)
  • Cyanobacteria
  • Internal carbon pool
  • Nitrate

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