samples showed low BLAST identities (<95%) suggesting that these soils may
harbor unique, novel taxa.
Two diazotrophic haloalkaliphiles, Natronobacillus azotifigens from solonchak
soil in the Kulunda Steppe in Russia [64] and Anaerobacillus alkalidiazotrophicus
(former Bacillus alkalidiazotrophicus) from northeastern Mongolia solonchak samples [65] have been isolated by Sorokin. The authors concluded that both nitrogenfixing organisms, together with B. arseniciselenatis and Paenibacillus spp., form a
separate cluster on the tree of the nifH gene, and, thus, there is more to the ability of
the Gram-positive bacteria (other than clostridia) to fix nitrogen that is currently
recognized. Later, Sorokin and coworkers have been conducting more detailed study
on the solonchak samples [66]. Although it concerned only aerobic cultivated
hydrolytic species, the work performed made possible to assess the rich potential
of solonchak soils as a source of new extremophilic microorganisms. Using samples
of solonchak soils with pH > 9 brought from eight regions of the Earth, it was shown
that these soils are inhabited mainly by the two largest groups of bacteria belonging
to the phyla Actinobacteria and Firmicutes. The Actinobacteria were mostly
represented by two genera Nocardiopsis and Streptomyces, and the Firmicutes was
expectedly represented by genus Bacillus. Of course, this study was not exhaustive,
but the trend is obvious, and other genera belonging to these two phyla will
eventually be isolated from saline soda soils.
Transitional formations between saline-alkaline soils and soda lakes (so-called
salt pans) have an alkaline pH and can also serve as a source of alkaliphilic
microorganisms. Examples are Jeotgalibacillus alkaliphilus (tolerates up to 24%
(w/v) NaCl) isolated from the salt pan near seashore in India [67], Alkalibacillus
almallahensis from an inland solar saltern in Spain [68], Nesterenkonia pannonica
[69], Nitrincola alkalilacustris, and Nitrincola schmidtii [70] from the salt pan
located in Kiskunság National Park in Hungary.
2.4 A Near-Bottom Alkaline Sites
A small-scale natural alkaline environment has been found in ikaite (CaCO 3 Á6H 2 O)
tufa columns which harbor the bottom of the Ikka Fjord in southwest Greenland.
Ikaite columns are formed when alkaline freshwater springs rich in sodium carbonates meet the cold, calcium-rich seawater, which leads to an immediate oversaturation
of calcium and carbonate ions and a subsequent growth of the column. The interior is
filled with a cold (4
C), alkaline (pH 10.4), and low salinity (0.9%) spring water
floating through the column, and this peculiar environment harbors a large diversity
of bacterial species [71, 72]. The 16S rRNA gene sequences from 67 cultured isolates
and 109 clone library phylotypes showed similarity to phylotypes of 6 bacterial phyla
where Alphaproteobacteria and Gammaproteobacteria dominated, and 22 of the
67 ikaite isolates showed less than 97% sequence similarity to sequences from known
species. The place seems promising in terms of the search and isolation of new
alkaliphiles as producers of a diversity of enzymes, and researchers succeeded in
62
V. V. Kevbrin
harbor unique, novel taxa.
Two diazotrophic haloalkaliphiles, Natronobacillus azotifigens from solonchak
soil in the Kulunda Steppe in Russia [64] and Anaerobacillus alkalidiazotrophicus
(former Bacillus alkalidiazotrophicus) from northeastern Mongolia solonchak samples [65] have been isolated by Sorokin. The authors concluded that both nitrogenfixing organisms, together with B. arseniciselenatis and Paenibacillus spp., form a
separate cluster on the tree of the nifH gene, and, thus, there is more to the ability of
the Gram-positive bacteria (other than clostridia) to fix nitrogen that is currently
recognized. Later, Sorokin and coworkers have been conducting more detailed study
on the solonchak samples [66]. Although it concerned only aerobic cultivated
hydrolytic species, the work performed made possible to assess the rich potential
of solonchak soils as a source of new extremophilic microorganisms. Using samples
of solonchak soils with pH > 9 brought from eight regions of the Earth, it was shown
that these soils are inhabited mainly by the two largest groups of bacteria belonging
to the phyla Actinobacteria and Firmicutes. The Actinobacteria were mostly
represented by two genera Nocardiopsis and Streptomyces, and the Firmicutes was
expectedly represented by genus Bacillus. Of course, this study was not exhaustive,
but the trend is obvious, and other genera belonging to these two phyla will
eventually be isolated from saline soda soils.
Transitional formations between saline-alkaline soils and soda lakes (so-called
salt pans) have an alkaline pH and can also serve as a source of alkaliphilic
microorganisms. Examples are Jeotgalibacillus alkaliphilus (tolerates up to 24%
(w/v) NaCl) isolated from the salt pan near seashore in India [67], Alkalibacillus
almallahensis from an inland solar saltern in Spain [68], Nesterenkonia pannonica
[69], Nitrincola alkalilacustris, and Nitrincola schmidtii [70] from the salt pan
located in Kiskunság National Park in Hungary.
2.4 A Near-Bottom Alkaline Sites
A small-scale natural alkaline environment has been found in ikaite (CaCO 3 Á6H 2 O)
tufa columns which harbor the bottom of the Ikka Fjord in southwest Greenland.
Ikaite columns are formed when alkaline freshwater springs rich in sodium carbonates meet the cold, calcium-rich seawater, which leads to an immediate oversaturation
of calcium and carbonate ions and a subsequent growth of the column. The interior is
filled with a cold (4
C), alkaline (pH 10.4), and low salinity (0.9%) spring water
floating through the column, and this peculiar environment harbors a large diversity
of bacterial species [71, 72]. The 16S rRNA gene sequences from 67 cultured isolates
and 109 clone library phylotypes showed similarity to phylotypes of 6 bacterial phyla
where Alphaproteobacteria and Gammaproteobacteria dominated, and 22 of the
67 ikaite isolates showed less than 97% sequence similarity to sequences from known
species. The place seems promising in terms of the search and isolation of new
alkaliphiles as producers of a diversity of enzymes, and researchers succeeded in
62
V. V. Kevbrin