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Regulation of nitrogen metabolism in the marine diazotroph Trichodesmium IMS101 under varying temperatures and atmospheric CO 2 concentrations
Author(s) -
Levitan Orly,
Brown Christopher M.,
Sudhaus Stefanie,
Campbell Douglas,
LaRoche Julie,
BermanFrank Ilana
Publication year - 2010
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2010.02195.x
Subject(s) - biology , trichodesmium , nitrogenase , diazotroph , photosynthesis , glutamine synthetase , nitrogen fixation , cyanobacteria , nitrogen , nitrogen cycle , rubisco , nitrogen assimilation , respiration , carbon fixation , botany , enzyme , biochemistry , glutamine , bacteria , chemistry , amino acid , organic chemistry , genetics
Summary We examined the influence of forecasted changes in global temperatures and p CO 2 on N 2 fixation and assimilation in the ecologically important cyanobacterium Trichodesmium spp. Changes of mRNA transcripts ( nifH, glnA, hetR, psbA, psaB ), protein (nitrogenase, glutamine synthetase) pools and enzymatic activity (nitrogenase) were measured under varying p CO 2 and temperatures. High p CO 2 shifted transcript patterns of all genes, resulting in a more synchronized diel expression. Under the same conditions, we did not observe any significant changes in the protein pools or in total cellular allocations of carbon and nitrogen (i.e. C : N ratio remained stable). Independently of temperature, high p CO 2 (900 µatm) elevated N 2 fixation rates. Levels of the key enzymes, nitrogenase and glutamine synthetase that mediate nitrogen assimilation did not increase, implying that the high p CO 2 allowed higher reaction turnover rates through these key enzymes. Moreover, increased temperatures and high p CO 2 resulted in higher C : P ratios. The plasticity in phosphorous stoichiometry combined with higher enzymatic efficiencies lead to higher growth rates. In cyanobacteria photosynthesis, carbon uptake, respiration, N 2 fixation and nitrogen assimilation share cellular components. We propose that shifted cellular resource and energy allocation among those components will enable Trichodesmium grown at elevated temperatures and p CO 2 to extend its niche in the future ocean, through both tolerance of a broader temperature range and higher P plasticity.