Limnospira fusiformis harbors dinitrogenase reductase (nifH)-like genes, but does not show N2 fixation activity

0559447 - BC 2023 RIV NL eng J - Journal Article
Schagerl, M. - Angel, Roey - Donabaum, U. - Gschwandner, A. M. - Woebken, D.
Limnospira fusiformis harbors dinitrogenase reductase (nifH)-like genes, but does not show N2 fixation activity.
Algal Research-Biomass Biofuels and Bioproducts. Roč. 66, July (2022), č. článku 102771. ISSN 2211-9264. E-ISSN 2211-9264
Institutional support: RVO:60077344
Keywords : diazotrophic * growth * non-heterocytous * saline-alkaline * Spirulina
OECD category: Microbiology
Impact factor: 5.1, year: 2022
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S2211926422001424?via%3Dihub

East African soda lakes (EASLs), some of them world-renowned for their large flocks of flamingos, range amongst the most productive aquatic ecosystems worldwide. The non-heterocytous filamentous cyanobacterium Limnospira fusiformis (formerly Arthrospira fusiformis or Spirulina platensis), forming almost unialgal blooms, is supposed to be a key driver in those ecosystems and is gaining increasing attention because of its nutritional value. Compared to phosphorus and carbon availability, these lakes show reduced nitrogen supply. We studied the possibility of molecular nitrogen (N2) fixation in Limnospira, as contradictory statements have been published, and some closely related taxa were confirmed as N2 fixers (diazotrophs). We cultivated nine isolates originating from various EASLs under nitrate-rich and nitrate-depleted conditions. We detected dinitrogenase reductase (nifH)-like genes in all strains, however, the genes grouped within nifH cluster IV that mostly contains nitrogenases not functioning in N2 fixation. Accordingly, incubations with 15N2 gas did not support N2 fixation activity of the investigated strains. Under laboratory conditions, all strains faded during nitrate-depleted growth after approximately three weeks. Both phycocyanin and chlorophyll-a dropped to a threshold, and chlorophyll fluorescence indicated a severe problem with nitrogen supply. In summary, our data indicate that the investigated Limnospira fusiformis strains are not capable of N2 fixation.
Permanent Link: https://hdl.handle.net/11104/0336744