Natronobacillus azotifigens gen. nov., sp. nov., an anaerobic diazotrophic haloalkaliphile from soda-rich habitats |
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Authors: | I D Sorokin E V Zadorina I K Kravchenko E S Boulygina T P Tourova D Y Sorokin |
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Institution: | (1) Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/2, 117312 Moscow, Russia;(2) Bioengineering Centrum RAS, Prospect 60-let Octyabrya 7/2, 117312 Moscow, Russia;(3) Department of Biotechnology, Delft University of Technology, Delft, The Netherlands |
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Abstract: | Gram-positive bacteria capable of nitrogen fixation were obtained in microoxic enrichments from soda soils in south-western
Siberia, north-eastern Mongolia, and the Lybian desert (Egypt). The same organisms were obtained in anoxic enrichments with
glucose from soda lake sediments in the Kulunda Steppe (Altai, Russia) using nitrogen-free alkaline medium of pH 10. The isolates
were represented by thin motile rods forming terminal round endospores. They are strictly fermentative saccharolytic anaerobes
but tolerate high oxygen concentrations, probably due to a high catalase activity. All of the strains are obligately alkaliphilic
and highly salt-tolerant natronophiles (chloride-independent sodaphiles). Growth was possible within a pH range from 7.5 to
10.6, with an optimum at 9.5–10, and within a salt range from 0.2 to 4 M Na+, with an optimum at 0.5–1.5 M for the different strains. The nitrogenase activity in the whole cells also had an alkaline
pH optimum but was much more sensitive to high salt concentrations compared to the growing cells. The isolates formed a compact
genetic group with a high level of DNA similarity. Phylogenetic analysis based on 16S-rRNA gene sequences placed the isolates
into Bacillus rRNA group 1 as a separate lineage with Amphibacillus tropicus as the nearest relative. In all isolates the key functional nitrogenase gene nifH was detected. A new genus and species, Natronobacillus azotifigens gen. nov., sp. nov., is proposed to accommodate the novel diazotrophic haloalkaliphiles.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
The GenBank accession numbers for the 16S rRNA gene of the novel strains are EU143681-EU143690 and EU850814-EU850816; for
the nifH gene the accession numbers are EU542601, EU563380-EU563386 and EU850817-EU850819. |
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Keywords: | Nitrogen fixation Soda soils Soda lakes Haloalkaliphilic nifH gene Bacillus rRNA group 1 |
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