Quantifying Oxygen Management and Temperature and Light Dependencies of Nitrogen Fixation by Crocosphaera watsonii

0520329 - MBÚ 2020 RIV US eng J - Journal Article
Inomura, K. - Deutsch, C. - Wilson, S.T. - Masuda, Takako - Lawrenz, Evelyn - Bučinská, Lenka - Sobotka, Roman - Gauglitz, J.M. - Saito, M.A. - Prášil, Ondřej - Follows, M.J.
Quantifying Oxygen Management and Temperature and Light Dependencies of Nitrogen Fixation by Crocosphaera watsonii.
Science Signaling. Roč. 4, č. 6 (2019), č. článku e00531-19. ISSN 1945-0877. E-ISSN 1937-9145
R&D Projects: GA MŠMT(CZ) LO1416; GA ČR GA16-15467S
Institutional support: RVO:61388971
Keywords : Crocosphaera * carbon * cell flux model
OECD category: Microbiology
Impact factor: 6.467, year: 2019
Method of publishing: Limited access
https://msphere.asm.org/content/4/6/e00531-19

Crocosphaera is a major dinitrogen (N-2)-fixing microorganism, providing bioavailable nitrogen (N) to marine ecosystems. The N-2-fixing enzyme nitrogenase is deactivated by oxygen (O-2), which is abundant in marine environments. Using a cellular scale model of Crocosphaera sp. and laboratory data, we quantify the role of three O-2 management strategies by Crocosphaera sp. size adjustment, reduced O-2 diffusivity, and respiratory protection. Our model predicts that Crocosphaera cells increase their size under high O-2. Using transmission electron microscopy, we show that starch granules and thylakoid membranes are located near the cytoplasmic membranes, forming a barrier for O-2. The model indicates a critical role for respiration in protecting the rate of N-2 fixation. Moreover, the rise in respiration rates and the decline in ambient O-2 with temperature strengthen this mechanism in warmer water, providing a physiological rationale for the observed niche of Crocosphaera at temperatures exceeding 20 degrees C. Our new measurements of the sensitivity to light intensity show that the rate of N-2 fixation reaches saturation at a lower light intensity (similar to 100 mu mol m(-2) s(-1)) than photosynthesis and that both are similarly inhibited by light intensities of >500 mu mol m(-2) s(-1). This suggests an explanation for the maximum population of Crocosphaera occurring slightly below the ocean surface.

IMPORTANCE Crocosphaera is one of the major N-2-fixing microorganisms in the open ocean. On a global scale, the process of N-2 fixation is important in balancing the N budget, but the factors governing the rate of N-2 fixation remain poorly resolved. Here, we combine a mechanistic model and both previous and present laboratory studies of Crocosphaera to quantify how chemical factors such as C, N, Fe, and O-2 and physical factors such as temperature and light affect N-2 fixation.
Permanent Link: http://hdl.handle.net/11104/0305018