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

Michael Schagerl (Korresp. Autor*in), Roey Angel, Ulrich Donabaum, Anna-Maria Gschwandner, Dagmar Wöbken

Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

Abstract

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.
OriginalspracheEnglisch
Aufsatznummer102771
Seitenumfang11
FachzeitschriftAlgal Research
Jahrgang66
Frühes Online-Datum2 Juli 2022
DOIs
PublikationsstatusVeröffentlicht - 3 Juli 2022

ÖFOS 2012

  • 106026 Ökosystemforschung
  • 106022 Mikrobiologie

Zitationsweisen