The patterns of nitrogen fixation in haloalkaliphilic phototrophic communities of Kulunda Steppe soda lakes (Altai, Russia)

Olga S. Samylina, Zorigto B. Namsaraev, Natalia V. Slobodova, Vladimir V. Zelenev, Gennadii V. Borisenko, Dimitry Y. Sorokin

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Abstract

Nitrogen fixation (NF) of phototrophic communities was studied in a number of soda lakes with a wide range of salinity (25-400 g/l) located in Kulunda Steppe (Altai, Russia) during several summer seasons (2011-2016). The phototrophic communities were represented by the algal-bacterial Ctenocladus communities or cyanobacterial biofilms dominated by heterocystous and non-heterocystous cyanobacteria and purple sulfur bacteria Ectothiorhodospira sp. (up to 210 g/l) and endoevaporitic Euhalothece communities dominated by the extremely salt-tolerant unicellular cyanobacterium Euhalothece sp. and Ectothiorhodospira sp. (above 350 g/l). Salinity was the major factor influencing the composition and NF potential of the phototrophic communities. The communities dominated by vegetative heterocystous cyanobacteria exhibited light-independent NF at total salinity up to 60 g/l. The communities dominated by non-heterocystous cyanobacteria exhibited light-dependent NF in a range of 55-100 g/l, but it was significantly suppressed at 100 g/l. At 160-200 g/l the dark heterotrophic NF was a prevailing process if communities didn't contain Euhalothece sp. At salt-saturating ranges above 350 g/l, light-dependent NF associated with the Euhalothece communities was detected. A statistically significant positive correlation between the NF and diurnal light intensity was found in all samples of communities dominated by non-heterocystous cyanobacteria in contrast to communities dominated by heterocystous cyanobacteria with insignificant correlation coefficients.

Original languageEnglish
Article numberfiz174
Number of pages13
JournalFEMS Microbiology Ecology
Volume95
Issue number11
DOIs
Publication statusPublished - 2019

Keywords

  • Ctenocladus
  • circadian rhythm
  • non-heterocystous cyanobacteria
  • phototrophic nitrogen fixation
  • soda lakes

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