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

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.

Unexpected Abundance and Diversity of Phototrophs in Mats from Morphologically Variable Microbialites in Great Salt Lake, Utah

“…Based on protein annotations, the GSL Euhalothece population is also likely capable of fermenting pyruvate into formate, lactate, and acetate and can convert dinitrogen (N 2 ) to ammonia via molybdenum (Mo)-dependent nitrogenase. This characteristic is consistent with recent reports of N 2 fixation in this genus (35) and indicates that Euhalothece likely supplies both fixed carbon and nitrogen for secondary consumers in GSL. As such, Euhalothece likely represents a keystone species in the GSL mat community and the broader ecosystem (23,36).…”

Isachenkonia alkalipeptolytica gen. nov. sp. nov., a new anaerobic, alkaliphilic proteolytic bacterium capable of reducing Fe(III) and sulfur

“…Recent microbiological studies of Kulunda steppe soda lakes have led to the isolation of several new taxa of alkaliphilic prokaryotes [18–27] and to the characterization of various microbial processes taking place in these habitats [28–39]. In particular, it was shown that the dead biomass of the primary producers could serve as a source of proteins and peptides for numerous proteolytic bacteria, including members of the phylum Firmicutes Proteinivorax tanatarense [40, 41] and Proteinivorax hydrogeniformans [42] or Candidatus ‘Cyclonatronum proteinivorum’ of the phylum Balneolaeota [43].…”

Haloalkalitolerant Fungi from Sediments of the Big Tambukan Saline Lake (Northern Caucasus): Diversity and Antimicrobial Potential

“…High salt concentrations and alkaline pH values in natural habitats yield the emergence of specific communities of prokaryotic and eukaryotic organisms, with a pronounced dominance of a small number of adapted species [1][2][3][4][5][6]. Every part of the community plays its own role and is strongly connected to the other parts [7][8][9].…”