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Int J Syst Evol Microbiol 57 (2007), 2762-2769; DOI  10.1099/ijs.0.64955-0
© 2007 International Union of Microbiological Societies

Methylohalomonas lacus gen. nov., sp. nov. and Methylonatrum kenyense gen. nov., sp. nov., methylotrophic gammaproteobacteria from hypersaline lakes

Dimitry Yu. Sorokin1,2, Yuri A. Trotsenko3, Nina V. Doronina3, Tatjana P. Tourova1, Erwin A. Galinski4, Tatjana V. Kolganova5 and Gerard Muyzer2

1 Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/2, 117811 Moscow, Russia
2 Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
3 G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Russia
4 Institute of Microbiology and Biotechnology, Rheinische Friedrich-Wilhelms University, Meckenheimer Allee 168, 53115 Bonn, Germany
5 Center Bioengineering, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/1, 117312 Moscow, Russia

Correspondence
Dimitry Yu. Sorokin
soroc{at}inmi.host.ru
or
D.Y.Sorokin{at}tnw.tudelft.nl


   ABSTRACT
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Aerobic enrichment at 4 M NaCl, pH 7.5, with methanol as carbon and energy source from sediments of hypersaline chloride–sulfate lakes in Kulunda Steppe (Altai, Russia) resulted in the isolation of a moderately halophilic and obligately methylotrophic bacterium, strain HMT 1T. The bacterium grew with methanol and methylamine within a pH range of 6.8–8.2 with an optimum at pH 7.5 and at NaCl concentrations of 0.5–4 M with an optimum at 2 M. In addition to methanol and methylamine, it can oxidize ethanol, formate, formaldehyde and dimethylamine. Carbon is assimilated via the serine pathway. The main compatible solute is glycine betaine. 16S rRNA gene sequence analysis placed the isolate as a new lineage in the family Ectothiorhodospiraceae (Gammaproteobacteria). It is proposed, therefore, to accommodate this bacterium within a novel genus and species, Methylohalomonas lacus gen. nov., sp. nov., with HMT 1T (=DSM 15733T =NCCB 100208T =UNIQEM U237T) as the type strain. Two strains were obtained in pure culture from sediments of soda lake Magadi in Kenya and the Kulunda Steppe (Russia) on a mineral medium at pH 10 containing 0.6 M total Na+ using methanol as a substrate. Strain AMT 1T was enriched with methanol, while strain AMT 3 originated from an enrichment culture with CO. The isolates are restricted facultative methylotrophs, capable of growth with methanol, formate and acetate as carbon and energy sources. With methanol, the strains grew within a broad salinity range from 0.3 to 3.5–4 M total Na+, with an optimum at 0.5–1 M. The pH range for growth was between 8.3 and 10.5, with an optimum at pH 9.5, which characterized the soda lake isolates as obligate haloalkaliphiles. Carbon is assimilated autotrophically via the Calvin–Benson cycle. Sequence analysis of the gene coding for the key enzyme RuBisCO demonstrated that strain AMT 1T possessed a single cbbL gene of the ‘green’ form I, clustering with members of the family Ectothiorhodospiraceae. Analysis of the 16S rRNA gene sequence showed that strains AMT 1T and AMT 3 belong to a single species that forms a separate lineage within the family Ectothiorhodospiraceae. On the basis of phenotypic and genetic data, the novel haloalkaliphilic methylotrophs are described as representing a novel genus and species, Methylonatrum kenyense gen. nov., sp. nov. (type strain AMT 1T =DSM 15732T =NCCB 100209T =UNIQEM U238T).

Abbreviations: EPS, exopolysaccharide

The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains HMT 1T, AMT 1T and AMT 3 are DQ834966, DQ789390 and EU006088, respectively. Those for the cbbL gene from AMT 1T and for the mxaF gene from HMT 1T are respectively EF152335 and EF152336.

Fatty acid compositions of isolates AMT 1T and HMT 1T and results of PCR amplifications of mxaF with four different primer sets from (halo)alkaliphilic methylotrophs are available as supplementary material with the online version of this paper.


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Hypersaline inland lakes occur as two major types: chloride–sulfate lakes, with a neutral to slightly alkaline pH (6–8.5), and soda lakes, where the presence of free carbonate/bicarbonate can reach molar concentrations, resulting in the accumulation of highly alkaline brines with a pH from 9.5 to 11. Both lake types are populated almost entirely by prokaryotes belonging to specialized (halo)alkaliphilic ecotypes. Most of these lakes are highly productive, with nitrogen-fixing (halo)alkaliphilic cyanobacteria as dominant primary producers. Various types of (halo)alkaliphilic anaerobic prokaryotes, including fermentative bacteria, methanogens and sulfate-reducing bacteria, are responsible for the complete degradation of organic matter, resulting in the formation of sulfide and methane as final products (Oren, 2002Go; Zavarzin et al., 1999Go). Methanotrophic and methylotrophic bacteria utilize the C1 compounds produced from anaerobic degradation of organic matter, thus closing the carbon cycle. Furthermore, in hypersaline habitats, the total flux of methylated compounds is enhanced by their formation as a degradation product from osmolytes, such as glycine betaine and dimethyl sulfoniopropionate. Also, haloalkaliphilic methanotrophic bacteria are known to excrete substantial amounts of C1 intermediates during methane oxidation (Trotsenko & Khmelenina, 2002aGo, bGo). Measurements with 14C1 compounds have demonstrated low but detectable rates of degradation in sediments of hypersaline lakes, indicating the presence of methano- and methylotrophic bacteria active under high salt conditions (Oremland et al., 1982Go; Sokolov & Trotsenko, 1995Go; Namsaraev et al., 1999Go; Joye et al., 1999Go; Sorokin et al., 2004Go). Nevertheless, the (halo)alkaliphilic methano- and methylotrophic bacteria isolated so far in pure culture from saline lakes all belong to a low-salt-tolerant type (Trotsenko & Khmelenina, 2002aGo, bGo; Heyer et al., 2005Go; Doronina et al., 2000Go, 2001Go, 2003aGo, bGo). The only exception is a halophilic methanotroph, Methylohalobius crimeensis 10KiT, capable of growth with up to 15 % NaCl (Heyer et al., 2005Go).

In this paper, we describe the isolation and properties of two novel species of methylotrophic gammaproteobacteria from hypersaline lakes capable of growth with C1 compounds up to salt-saturating conditions.

The Kulunda Steppe (Altai, Russia) harbours numerous salt lakes with a total salt content from 10 to 38 % and a pH of 7.0–8.5, with Na+, Mg2+, Cl– and Formula as the dominant ions in the brines. Samples of the top 10 cm of sediment with overlying brine water from ten lakes were mixed and used as an inoculum to enrich for halophilic methylotrophic bacteria. A sediment sample from the hypersaline soda lake Magadi (Kenya), pH 10.5 and total salt content of 22 %, was used to enrich for haloalkaliphilic methylotrophs.

The mineral base medium used for enrichment of halophilic methylotrophs included 4 M NaCl, 10 mM K2HPO4 and 5 mM (NH4)2SO4, final pH 7.2. The mineral base for haloalkaliphiles contained sodium carbonate/bicarbonate buffer, pH 10, containing 0.6–4 M total Na+, 0.1 M NaCl, 10 mM K2HPO4 and 5 mM KNO3. After sterilization, the media were supplemented with 1 mM MgSO4 . 7H2O, 1 ml trace metal solution l–1 (Pfennig & Lippert, 1966Go), 100 µg vitamin B12 l–1 and 10 mM NaHCO3. Methanol (25 mM) served as the electron donor and carbon source. In an enrichment with CO as the only carbon and energy source from Kulunda Steppe lakes, methanol was replaced with 5 % CO in the gas phase (10 mM). After several consecutive additions of CO, the culture was transferred into medium with methanol. The incubation temperature was 30 °C. The isolation strategy included several 1 : 100 transfers to stabilize the cultures, serial dilutions and plating onto solid medium prepared by mixing at 50 °C of equal volumes of the liquid mineral base medium, indicated above, and 4 % (w/v) Noble agar (Difco). The plates were incubated in closed jars at 5 % O2. Autotrophic growth with hydrogen as electron donor was studied at optimal pH and salt using 100 ml serum bottles with 20 ml medium under an atmosphere of 50 % air and 50 % H2. To test for anaerobic growth with methanol (25 mM) and nitrate (20 mM), 80 ml medium was used in 100 ml serum bottles with argon in the gas phase.

Growth was monitored by measuring the OD600 and by cell protein analysis with the Lowry method. Respiration rates of washed cells were measured in mineral buffers corresponding to the growth medium composition without nitrogen sources using a Biological oxygen monitor (Yellow Spring Inc.). Activity of the key methylotrophic enzymes in cell-free extracts and the composition of membrane lipids and fatty acids were analysed as described previously (Doronina et al., 1995Go, 2003aGo). The composition of compatible solutes in the halophilic isolate HMT 1T was analysed by an HPLC/13C-NMR method according to Galinski & Herzog (1990)Go. Phase-contrast photomicrographs were obtained using a Zeiss Axioplan Imaging 2 microscope. For electron microscopy, cells were fixed with glutaraldehyde (final, 3 % v/v) and positively contrasted with 1 % (w/v) uranyl acetate. For thin sectioning, the cells were fixed in 1 % (w/v) OsO4 solution containing 0.5–1.0 M NaCl, dehydrated, embedded in resin and stained with uranyl acetate and lead citrate after sectioning. The isolation of DNA and subsequent determination of the G+C content and DNA–DNA hybridization were performed by the thermal denaturation/reassociation technique (Marmur, 1961Go; De Ley et al., 1970Go).

For molecular analysis, genomic DNA was extracted from cells using the UltraClean Soil DNA extraction kit (Mo Bio Laboratories), following the manufacturer's instructions. Nearly complete 16S rRNA genes were amplified by PCR from pure cultures using bacterial primers GM3F and GM4R (Schäfer & Muyzer, 2001Go). To amplify the cbbL gene, coding for the RuBisCO large subunit, a specially designed primer pair and protocol was employed (Spiridonova et al., 2004Go). Amplification of the mxaF gene, coding for methanol dehydrogenase, was performed with four different primer sets (McDonald & Murrell, 1997Go; Dedysh et al., 2005Go). The sequences obtained in this study were first compared to sequences stored in GenBank using the BLAST algorithm (http://www.ncbi.nlm.nih.gov/BLAST). The nucleotide and inferred amino acid sequences were aligned with sequences from GenBank using CLUSTAL W. Phylogenetic trees were reconstructed using the TREECONW (Van de Peer & De Wachter, 1994Go) and PHYLIP 3.5c (Felsenstein, 1993Go) program packages with four different algorithms: neighbour-joining, maximum-parsimony, distance matrix and maximum-likelihood.

The enrichment with methanol at 4 M NaCl using a mixture of sediment samples from hypersaline Siberian lakes resulted in the domination of rod-shaped bacteria, which were further purified by serial dilutions and eventually isolated in pure culture from a single colony on plates containing 2 M NaCl and methanol as strain HMT 1T. Among the enrichments from Lake Magadi at pH 10 with methanol as substrate, positive results were obtained only at low salt (0.6–1.0 M total Na+, but not at 3–4 M), resulting in isolation of strain AMT 1T. Another haloalkaliphilic methylotroph, strain AMT 3, was obtained from an enrichment inoculated with a mixed sediment sample from Kulunda Steppe hypersaline soda lakes where CO served as the only substrate. AMT 3 was a minor satellite component of that enrichment, but it became dominant after transfer into the medium with methanol.

Cells of all three isolates were short, non-motile rods with a Gram-negative type of cell wall (Fig. 1Go). Cells of strain HMT 1T were covered with an exopolysaccharide (EPS)-like substance.


Figure 1
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  		Fig. 1. Cell morphology of haloalkaliphilic strain AMT 1T (a, c) and halophilic strain HMT 1T (b, d) from hypersaline lakes. (a, b) Phase-contrast photomicrographs; (c, d) thin sections. Bars, 10 µm (a, b) and 1 µm (c, d).

 
Strain HMT 1T belonged to the obligate methylotrophs, utilizing only methanol and methylamine as growth substrates. In contrast, the soda lake isolates, in addition to utilizing methanol (AMT 1T, AMT 3) and formate (AMT 3), also grew on acetate and ethanol and therefore can be considered as restricted methylotrophs. According to its pH and salt response, the salt lake isolate HMT 1T is a neutrophilic, extremely salt-tolerant moderate halophile. To our knowledge, it represents the first halophilic, methylotrophic bacterium capable of growth with C1 compounds up to 4 M NaCl. The soda lake isolates are typical haloalkaliphiles, with a relatively narrow alkaline pH range for growth and an optimum at pH 10. Although isolated at low salt, in pure culture, strains AMT 1T and AMT 3 grew with methanol and acetate in saturated soda brines (3.5–4 M total Na+). This makes these strains unique among the haloalkaliphilic methylotrophs obtained from soda lakes so far. It needs to be mentioned, however, that, for all isolates, the growth rate at 3.5–4 M Na+ was only 5–10 % of the maximum (µmax with methanol 0.045 and 0.02–0.035 h–1 for halophilic strain HMT 1T and haloalkaliphilic strains AMT 1T and AMT 3, respectively), and the growth yield decreased by a factor of 2–2.5. This indicates highly stressed growth conditions. Autotrophic growth was not observed either with hydrogen or thiosulfate as electron donor, and anaerobic growth was not observed with nitrate. Respiration activity tests using washed cells demonstrated that, apart from methanol and its oxidation products (i.e. formate and formaldehyde), all three isolates can also oxidize ethanol. Furthermore, cells of HMT 1T induced methyl- and dimethylamine-oxidizing capacity when grown with methylamine, while still keeping the potential to oxidize methanol. On the other hand, growth of strains AMT 1T and AMT 3 with acetate led to repression of the methanol dehydrogenase system and induction of acetate-dependent respiration, while retaining high activities of formaldehyde oxidation (Table 1Go). The maximum rate of methanol-dependent respiration activity for halophilic strain HMT 1T was observed at pH 8 and 2 M NaCl and at pH 10 and 0.5–0.75 M total Na+ for the haloalkaliphilic strains AMT 1T and AMT 3.


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  		Table 1. Respiration activity of washed cells of (halo)alkaliphilic methylotrophic isolates

Cells were incubated under the same conditions of pH and salt composition with the C1 compound shown. Strains AMT 1T and AMT 3 were grown at pH 10 and 0.6 M Na+, while strain HMT 1T was grown at pH 7.5 and 2 M NaCl. Values are nmol O2 (mg protein)–1 min–1.

 
Measurements of the activity of key enzymes of C1 metabolism (Table 2Go) identified the presence of methanol-catabolizing dehydrogenases in strains HMT 1T and AMT 1T. However, their carbon assimilation pathways were different. In halophilic strain HMT 1T, the key enzymes of the serine pathway (hydroxypyruvate reductase and serine-glyoxylate aminotransferase) were detected. In contrast, the haloalkaliphilic strain AMT 1T is an autotroph, with the Calvin–Benson cycle and RuBisCO and phosphoribulokinase as the key enzymes.


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  		Table 2. Enzyme activities in cell-free extracts of methylotrophic extremophilic bacteria

The growth substrate was methanol. Cells were incubated under the same conditions of pH and salt as in the growth media. Activities are given as nmol (mg protein)–1 min–1. Strain AMT 1T was grown at pH 10 and 0.6 M Na+ and strain HMT 1T was grown at pH 7.5 and 2 M NaCl. GSH, Reduced glutathione; PMS, phenazine methosulfate.

 
Lipid analysis revealed the presence of cardiolipin, phosphatidylethanolamine and phosphatidylserine as the major membrane phospholipids in strains HMT 1T and AMT 1T. However, the cellular fatty acid compositions were very different in the two strains (Supplementary Table S1, available in IJSEM Online). The fatty acid profile in the haloalkaliphilic methylotroph AMT 1T was very similar to that of the low-salt-tolerant, alkaliphilic, sulfur-oxidizing autotroph Thioalkalimicrobium aerophilum, isolated from the same habitats (Banciu et al., 2005Go), with an absolute dominance of C18 : 1{omega}7. In the neutrophilic halophile HMT 1T, saturated species were dominant, with C16 : 0 as a predominant component and cyc C17 : 0 and 10-methyl C16 : 0 as secondary dominant components. While the former is quite common for halophiles (Vargas et al., 2005Go), the abundance of cyc C17 : 0 and complete absence of C18 : 1 species is certainly unusual. As for the third abundant species, 10-methyl C16 : 0, our recent work with two new groups of extremely halophilic, sulfur-oxidizing gammaproteobacteria obtained from the same habitats (Sorokin et al., 2006Go) identified it as a dominant fatty acid in their polar membrane lipids. Analysis of organic compatible solute composition accumulated by the cells of halophilic strain HMT 1T grown with methanol at 2 M NaCl demonstrated the presence of glycine betaine as the dominant species, constituting approximately 17 % of the total cell mass. This solute and its specific content are typical for high-salt-tolerant (halo)alkaliphilic gammaproteobacteria (Galinski & Trüper, 1994Go).

The G+C contents in the genomic DNA of strains AMT 1T, AMT 3 and HMT 1T were 59.6, 59.0 and 62.9 mol% (Tm), respectively. Phylogenetic analysis based on sequencing of the 16S rRNA gene placed the extremophilic methylotrophs into the family Ectothiorhodospiraceae. According to this analysis, the AMT strains clearly belonged to the same species (99.7 % sequence similarity). The group was loosely associated with sequences from non-phototrophic members of the Ectothiorhodospiraceae, such as the Alkalispirillum–Alkalilimnicola group, Aquisalina and Arhodomonas aquaeolei (Fig. 2Go). The nearest culturable relative of the halophilic strain HMT 1T is the haloalkaliphilic sulfur-oxidizing bacterium Thioalkalispira microaerophila ALEN 1T, isolated from a soda lake (Sorokin et al., 2002Go). It must be noted that HMT 1T represents the first example of a methylotroph with the serine pathway of carbon assimilation within the Gammaproteobacteria. In both cases, the level of 16S rRNA gene sequence similarity with the nearest relatives was below 95 %.


Figure 2
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  		Fig. 2. Neighbour-joining tree based on 16S rRNA gene sequences showing the phylogenetic affiliations of (halo)alkaliphilic methylotrophic isolates from hypersaline lakes within the Gammaproteobacteria. Bar, 5 % sequence variation. Bootstrap values indicated at nodes are presented only when they exceed 70 %.

 
Since both the alkaliphilic and halophilic isolates formed deep lineages with uncertain branching, key functional genes cbbL (RuBisCO) for the alkaliphilic strain AMT 1T and mxaF (methanol dehydrogenase) for both groups were also analysed. A single cbbL gene of the ‘green-like’ form I RuBisCO was detected in AMT 1T. Phylogenetic analysis placed the sequence within the Thioalkalivibrio cluster in the Ectothiorhodospiraceae, consistent with the 16S rRNA gene phylogeny (Fig. 3aGo). The mxaF gene was easily detectable in the halophilic isolate HMT 1T, but all attempts to amplify the gene from the AMT strains, using four different primer sets, failed (Supplementary Fig. S1). This might indicate that the enzyme in this autotrophic methylotroph is different from the classical methanol dehydrogenase. Phylogenetic analysis of the partial mxaF sequence from HMT 1T placed it between beta- and gammaproteobacterial methylotrophs as a separate branch, which confirmed its separate position among known methylotrophs (Fig. 3bGo).


Figure 3
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  		Fig. 3. Phylogenetic positions of methylotrophic isolates based on translated amino acid analysis of functional genes. (a) Position of haloalkaliphilic isolate AMT 1T based on cbbL gene sequence analysis (large subunit of RuBisCO); (b) position of halophilic strain HMT 1T based on sequence analysis of the mxaF gene (methanol dehydrogenase). Tree topologies and evolutionary distances are given by the neighbour-joining method with Poisson corrections. Numbers at nodes indicate percentage bootstrap values from 1000 replications. Bars, 10 % (a) and 5 % (b) sequence variation.

 
On the basis of phenotypic and genetic properties, the novel (halo)alkaliphilic methylotrophic gammaproteobacteria isolated from hypersaline lakes are proposed to be assigned into two new genera and species. For the halophilic neutrophilic strain HMT 1T, the name Methylohalomonas lacus gen. nov., sp. nov. is proposed, and the name Methylonatrum kenyense gen. nov., sp. nov. is proposed for the haloalkaliphilic strains AMT 1T and AMT 3. Their essential properties in comparison with known (halo)alkaliphilic methylotrophs are presented in Table 3Go.


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  		Table 3. Comparative properties of (halo)alkaliphilic methylotrophic bacteria from salt lakes

Strains: 1, HMT 1T (data from this study); 2, AMT 1T and AMT3 (this study); 3, Methylophaga alcalica M39T (Doronina et al., 2003aGo); 4, ‘Methylophaga natronica’ Bur 2 (Doronina et al., 2003bGo); 5, ‘Ancylobacter natronum’ Bur 3 (Doronina et al., 2001Go); 6, Methylarcula terricola h37T (Doronina et al., 2000Go). RuMP, Ribulose monophosphate pathway; ND, no data available.

 
Description of Methylohalomonas gen. nov.
Methylohalomonas [Me.thy'lo.ha.lo.mo'nas. N.Gr. n. methyl (from Gr. n. methu wine and Gr. n. hulê wood) the methyl radical; Gr. n. hals, halos salt; Gr. fem. n. monas a unit, monad; N.L. fem. n. Methylohalomonas salt (-tolerant), methyl-group-utilizing monad].

Cells are Gram-negative rods. Obligately methylotrophic. Utilize C1 compounds as carbon and energy sources using the serine cycle for carbon assimilation. Halophilic and neutrophilic. C16 : 0, cyc C17 : 0 and 10-methyl C16 : 0 are the dominant cellular fatty acids. The genus belongs to the Gammaproteobacteria. Known habitat is hypersaline chloride–sulfate lakes. Methylohalomonas lacus is the type species.

Description of Methylohalomonas lacus sp. nov.
Methylohalomonas lacus (la'cus. L. gen. n. lacus of a lake).

Displays the following properties in addition to those described for the genus. Cells are non-motile (0.5–0.6x1–3 µm), occurring singly or in short chains, and covered with a layer of EPS-like material. Strictly aerobic, utilizing methanol and methylamine as carbon and energy sources. With methanol, grows at pH 6.5–8.2 (optimum pH 7.5). Extremely salt-tolerant, moderate halophile with a NaCl range for growth between 0.5 and 4 M and an optimum at 2 M. Unable to grow autotrophically with H2 or thiosulfate as the energy source. Ammonium serves as a nitrogen source. The G+C content in the DNA of the type strain is 59.6 mol%.

The type strain, HMT 1T (=DSM 15733T =NCCB 100208T =UNIQEM U237T), was isolated from hypersaline inland lakes in south-western Siberia (Altai, Russia).

Description of Methylonatrum gen. nov.
Methylonatrum [Me.thy'lo.na.trum. N.Gr. n. methyl (from Gr. n. methu wine and Gr. n. hulê wood) the methyl radical; N.Gr. n. natron arbitrarily derived from the Arabic n. natrun or natron soda; N.L. neut. n. Methylonatrum methyl-group-utilizing, soda (-loving bacterium)].

Cells are Gram-negative, short rods. Obligately aerobic, restricted methylotrophs. Autotrophic Calvin–Benson cycle is used for carbon assimilation during methylotrophic growth. Moderately salt-tolerant and obligately alkaliphilic. C18 : 1{omega}7 is the dominant cellular fatty acid. The genus belongs to the Gammaproteobacteria. Known habitat is soda lakes. Methylonatrum kenyense is the type species.

Description of Methylonatrum kenyense sp. nov.
Methylonatrum kenyense (ken.yen'se. N.L. neut. adj. kenyense pertaining to Kenya, where the type strain was isolated).

Displays the following properties in addition to those described for the genus. Cells are short, coccoid, non-motile rods (0.5–0.7x1–1.2 µm), occurring singly or in pairs. Utilizes methanol, formate, ethanol and acetate as carbon and energy sources. With methanol, grows at pH 8.3–10.5 (optimum pH 10). Extremely salt-tolerant, growing at salt contents between 0.3 and 4 M total Na+ with an optimum at 0.5–1.0 M. Can not grow autotrophically with H2 or thiosulfate as the energy source. Utilizes ammonium and nitrate as nitrogen sources. G+C content in the DNA is 62–62.9 mol%.

The type strain, AMT 1T (=DSM 15732T =NCCB 100209T =UNIQEM U238T), was isolated from the soda lake Magadi in Kenya. The closely related strain AMT 3 (=NCCB 100206) originated from soda lakes in the Kulunda Steppe (Altai, Russia).


   ACKNOWLEDGEMENTS
 
This work was supported by NWO-RFBR (047.011.2004.010) and RFBR (07-04-00153, 05-04-48058 and 05-04-4864) and by the Program on Molecular and Cell Biology RAS. We are grateful to M. Stein for compatible solute analysis.


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