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Heterotrophic denitrification at extremely high salt and pH by haloalkaliphilic Gammaproteobacteria from hypersaline soda lakes

Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/2, 117811 Moscow, Russia.
Extremophiles (Impact Factor: 2.31). 06/2008; 12(5):619-25. DOI: 10.1007/s00792-008-0166-6
Source: PubMed


In this paper we describe denitrification at extremely high salt and pH in sediments from hypersaline alkaline soda lakes and soda soils. Experiments with sediment slurries demonstrated the presence of acetate-utilizing denitrifying populations active at in situ conditions. Anaerobic enrichment cultures at pH 10 and 4 M total Na+ with acetate as electron donor and nitrate, nitrite and N2O as electron acceptors resulted in the dominance of Gammaproteobacteria belonging to the genus Halomonas. Both mixed and pure culture studies identified nitrite and N2O reduction as rate-limiting steps in the denitrification process at extremely haloalkaline conditions.

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    • "In this case, no accumulation of nitrites was measured. This suggests that the optimum pH of the nitrite reductase of Hd is located around 11 in the chemical conditions of the experiment, similarly to the findings of Shapovalova et al. (2008) for Halomonas strain AGD3. The absence of nitrate and/or nitrite in the outlet of the bioreactor prevents further growth of Hd in the exposure chamber and explains why acetate concentration did not change after the passage through the exposure chamber. "
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    • "It is unfortunate that all these reported halophilic species only grew and actively denitrified under aerobic conditions. Because of the low concentrations of dissolved oxygen in industrial wastewaters, these reported aerobic halophilic species were not suitable for application in treatment of industrial wastewater (Shapovalova et al., 2008). The objective of this research was to isolate and characterize new halophilic denitrifying bacteria with better potential for saline industrial wastewater treatment . "
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    • "Chemoheterotophic aerobes thriving in soda lakes are well represented by archaea, as well as Gram-negative and Gram-positive bacteria. Haloalkaliphilic members of the family Halomonadaceae (e.g., Halomonas magadiensis , H. kenyensis , H. mongoliensis ) have been isolated from soda lakes around the world, being an important part of the easily culturable aerobic chemoheterotrophic communities thriving in these ecosystems (Duckworth et al., 1996Duckworth et al., , 2000 Boltyanskaya et al., 2007 ; Shapovalova et al., 2008 ) . Other haloalkalitolerant and haloalkaliphilic Halomonas spp. "
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