The use of NH4+ rather than NO3- affects cell stoichiometry, C allocation, photosynthesis and growth in the cyanobacterium Synechococcus sp UTEX LB 2380, only when energy is limiting

0473758 - MBÚ 2018 RIV US eng J - Journal Article
Ruan, Z. - Giordano, Mario
The use of NH4+ rather than NO3- affects cell stoichiometry, C allocation, photosynthesis and growth in the cyanobacterium Synechococcus sp UTEX LB 2380, only when energy is limiting.
Plant Cell and Environment. Roč. 40, č. 2 (2017), s. 227-236. ISSN 0140-7791. E-ISSN 1365-3040
Institutional support: RVO:61388971
Keywords : carbon allocation * cyanobacteria * elemental stoichiometry
OECD category: Microbiology
Impact factor: 5.415, year: 2017

The assimilation of N-NO3- requires more energy than that of N-NH4+. This becomes relevant when energy is limiting and may impinge differently on cell energy budget depending on depth, time of the day and season. We hypothesize that N-limited and energy-limited cells of the oceanic cyanobacterium Synechococcus sp. differ in their response to the N source with respect to growth, elemental stoichiometry and carbon allocation. Under N limitation, cells retained almost absolute homeostasis of elemental and organic composition, and the use of NH4+ did not stimulate growth. When energy was limiting, however, Synechococcus grew faster in NH4+ than in NO3- and had higher C (20%), N (38%) and S (30%) cell quotas. Furthermore, more C was allocated to protein, whereas the carbohydrate and lipid pool size did not change appreciably. Energy limitation also led to a higher photosynthetic rate relative to N limitation. We interpret these results as an indication that, under energy limitation, the use of the least expensive N source allowed a spillover of the energy saved from N assimilation to the assimilation of other nutrients. The change in elemental stoichiometry influenced C allocation, inducing an increase in cell protein, which resulted in a stimulation of photosynthesis and growth.
Permanent Link: http://hdl.handle.net/11104/0270897