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Microbial thiocyanate utilization under highly alkaline conditions.
D Y Sorokin1, T P Tourova, A M Lysenko
1Institute of Microbiology RAS, 117811 Moscow, Russia.
Applied and Environmental Microbiology
|February 7, 2001
Summary
Alkaliphilic bacteria in soda lakes can utilize thiocyanate (CNS-) as a nitrogen or energy source. A novel "cyanate pathway" was identified, buffering ammonia toxicity in these extreme environments.
Area of Science:
- Microbiology
- Environmental Science
- Biochemistry
Background:
- Alkaline environments, such as soda lakes, harbor unique microbial communities adapted to high pH.
- Thiocyanate (CNS-) is an inorganic compound that can serve as a nutrient source for certain microorganisms.
- Understanding microbial metabolism in extreme environments is crucial for biogeochemical cycling and biotechnology.
Purpose of the Study:
- To isolate and characterize alkaliphilic bacteria capable of utilizing thiocyanate at pH 10.
- To investigate the metabolic pathways involved in thiocyanate degradation by these bacteria.
- To determine the phylogenetic relationships of these novel microorganisms.
Main Methods:
- Enrichment and isolation of bacteria from soda lake sediments and soils.
- Cultivation under highly alkaline conditions (pH 10) using thiocyanate as a substrate.
- Biochemical assays to determine metabolic capabilities (e.g., carbon source utilization, sulfur oxidation).
- Genetic and phylogenetic analyses (e.g., DNA homology, 16S rRNA gene sequencing).
Main Results:
- Three distinct groups of alkaliphilic bacteria utilizing thiocyanate were identified: obligate heterotrophs, obligate autotrophic sulfur-oxidizers using thiocyanate as a nitrogen source, and obligate autotrophs using thiocyanate as an energy source.
- Phylogenetic analysis placed heterotrophs within the Halomonas group and autotrophs within the Thioalkalivibrio genus (gamma-Proteobacteria).
- A novel "cyanate pathway" was demonstrated in thiocyanate-degrading bacteria, involving cyanase activity and cyanate accumulation, which likely acts as an ammonia buffer.
Conclusions:
- Alkaliphilic bacteria in soda lakes possess diverse metabolic strategies for utilizing thiocyanate.
- The identified "cyanate pathway" is a significant adaptation for survival in high-ammonia environments.
- These findings expand our understanding of microbial life and biogeochemical processes in extreme alkaline ecosystems.