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Contemporaneous N(2) Fixation and Oxygenic Photosynthesis in the Nonheterocystous Mat-Forming Cyanobacterium Lyngbya Aestuarii

Contemporaneous N(2) Fixation and Oxygenic Photosynthesis in the Nonheterocystous Mat-Forming Cyanobacterium Lyngbya Aestuarii

H W Paerl, L E Prufert, W W Ambrose

Appl Environ Microbiol. 1991 Nov;57(11):3086-92.

PMID: 16348576

Abstract:

The nonheterocystous filamentous cyanobacterial genus Lyngbya is a widespread and frequently dominant component of marine microbial mats. It is suspected of contributing to relatively high rates of N(2) fixation associated with mats. The ability to contemporaneously conduct O(2)-sensitive N(2) fixation and oxygenic photosynthesis was investigated in Lyngbya aestuarii isolates from a North Carolina intertidal mat. Short-term (<4-h) additions of the photosystem II (O(2) evolution) inhibitor 3(3,4-dichlorophenyl)-1,1-dimethylurea stimulated light-mediated N(2) fixation (nitrogenase activity), indicating potential inhibition of N(2) fixation by O(2) production. However, some degree of light-mediated N(2) fixation in the absence of 3(3,4-dichlorophenyl)-1,1-dimethylurea was observed. Electron microscopic immunocytochemical localization of nitrogenase, coupled to microautoradiographic studies of CO(2) fixation and cellular deposition of the tetrazolium salt 2,4,5-triphenyltetrazolium chloride, revealed that (i) nitrogenase was widely distributed throughout individual filaments during illuminated and dark periods, (ii) CO(2) fixation was most active in intercalary regions, and (iii) daylight 2,4,5-triphenyltetrazolium chloride reduction (formazan deposition) was most intense in terminal regions. Results suggest lateral partitioning of photosynthesis and N(2) fixation during illumination, with N(2) fixation being confined to terminal regions. During darkness, a larger share of the filament appears capable of N(2) fixation.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP531522	1,3,5-Triphenyltetrazolium formazan		531-52-2	Price

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