Abstract
Stable development of a heterotrophic bacterial satellite with a peculiar cell morphology has been observed in several enrichment cultures of haloalkaliphilic benthic filamentous cyanobacteria from a hypersaline soda lake in Kulunda Steppe (Altai, Russia). The organism was isolated in pure culture (strain Omega) using sonicated cyanobacterial cells as substrate and it was identified as a deep phylogenetic lineage within the recently proposed phylum Balneolaeota. It is an obligately aerobic heterotroph utilizing proteins and peptides for growth. The cell morphology significantly varied from semicircles to long filaments depending on the growth conditions. The cultures are red-orange colored due to a presence of carotenoids. The isolate is an obligate alkaliphile with a pH range for growth from 8.5 to 10.5 (optimum at 9.5–10) and moderately salt-tolerant with a range from 0.3 to 3 M total Na+ (optimum at 1 M). The genome analysis of strain Omega demonstrated a presence of gene, encoding a proteorhodopsin forming a separate branch in the sodium-translocating proteorhodopsin family. Experiments with washed cells of Omega confirmed light-dependent sodium export. A possible physiological role of the sodium proteorhodopsin in strain Omega is discussed. Phylogenomic analysis demostrated that strain Omega forms an deep, independent branch of a new genus and family level within a recently established phylum Balneolaeota.
Highlights
Soda lakes are a specific variety of salt lakes which brines are dominated by sodium carbonates resulting in molar alkalinity in solution and a stable pH around 10
We describe phenotypic and genomic properties of a moderately salt-tolerant alkaliphilic aerobic protein-utilizing bacterium which developed in a stable co-culture with soda lake benthic filamentous cyanobacteria
Microscopic examination of the pink layer showed a domination of a bacterium with peculiar cell morphology in the form of semicircles with only a few other rod-shaped bacteria (Figure 1a)
Summary
Soda lakes are a specific variety of salt lakes which brines are dominated by sodium carbonates resulting in molar alkalinity in solution and a stable pH around 10. Despite double extreme conditions of high salt-high pH, soda lakes, in general, are highly productive (Melack, 1981, 1988; Kompantseva et al, 2009) harboring diverse haloalkaliphilic communities dominated by Cyclonatronum proteinivorum gen. Haloalkaliphilic oxygenic cyanobacteria are the dominant primary producers in soda lakes. The evidences on their diversity are not abundant, . Nov., was shown to utilize the cell proteins produced by a soda lake benthic cyanobacterium Geitlerinema sp. For hypersaline conditions, three natronoarchaeal species have been shown to produce haloalkali-stable proteases at salt-saturated conditions and high pH by members of the genera Natronococcus, Natrialba, and Natronolimnobius (Studdert et al, 2001; Selim et al, 2014; Derntl et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
