molecules in fungus Sodiomyces tronii [114]), although eukaryotic biodiversity at
the alkaline pH is noticeably less than at near-neutral pH. Historically, alkaliphilic
eukaryotes from soda lakes have been studied in the most detail. Comprehensive
reviews of particular eukaryotes inhabiting African soda lakes (diatoms, green algae,
protozoa, invertebrates, fish, etc.) the reader can find in a valuable book edited by
Michael Schagerl [115], while eukaryotes from the other soda or alkaline lakes were
also the matter of exploring, e.g., picophytoplankton diversity in the Transylvanian
Basin (Romania) [116], fungi in the Mono Lake (USA) area [117], diatoms in Lake
Van [118], and assessment of the overall eukaryotic diversity in the three US
alkaline lakes plus a biofilm from the chimney at the Lost City hydrothermal vent
with a pH 11 [119]. The latter contemporary study has been fulfilled by the method
of massively parallel pyrotag sequencing targeting the V9 hypervariable region of
the 18S rRNA gene and aimed to compare eukaryotic communities living at acidic
(pH < 3) and alkaline (pH > 9) environments. It has been found that the number of
OTUs for alkaline lakes exceeds that for acid habitats, although the DNA derived
from allochthonous sources or environmental DNA (inactive or dead cells) may
contribute. It has been found that the most cosmopolitan OTU was a diatom
(Fragillariophyceae) that occurred both acidic and alkaline samples. Among the
shared alkaline OTUs were Frontonia and Lacrymaria (ciliates), Protaspa
(a cercozoan), a maxillopod metazoan OTU, a tracheophyte OTU and various
opisthokont OTUs including fungi. A unicellular chlorophyte Picocystis was expectedly found in the Mono Lake sample because this alga accounts for up to 50% of the
primary production there as it has been shown earlier [120].
In the 1980–1990s of the twentieth century, an interest of microbiologists to
alkaliphiles sparked the researchers to search for alkaliphilic fungi. Although the
ability of fungi to grow at pH 10 has been known for a long time [121], only a
targeted search for alkaliphilic fungi gave the first results in the beginning of the
1990s [122, 123]. The definition of alkaliphilicity at mycologists is slightly different
from that adopted by microbiologists. An earlier definition designated fungus which
could grow at pH up to 10, but not below pH 5–6, as alkaliphilic and those grew at
pH 10 and below pH 5–6 are regarded as alkalitolerant [122]. In a later definition, it
was proposed that fungal species be considered alkaliphilic provided their optimum
growth lies at pH above 8 and the acidic pH limit constraint 4–5 [124]. Among fungi
there are no species that would not grow at pH 7, so there are no fungal obligate
alkaliphiles in the “bacteriological sense.” The importance of using an alkaline
medium for the search for alkaliphilic fungi was already emphasized in the first
papers [122, 125]. However, the past decades of research have shown that the
diversity of, namely, alkaliphilic fungi by now, is not so large compared to
alkaliphilic bacteria, and the majority of species/genera of fungi/yeasts isolated at
pH 10 are often to be alkalitolerant [125–128].
This trend was recently confirmed in an extensive study, including morphological
and metagenomic analysis, on the search for alkaliphilic fungi from alkaline soils of
varying degrees of salinity sampled from Russia, Mongolia, Kazakhstan, Kenya,
Tanzania, and Armenia [124]. Among over 100 isolated strains assigning to various
taxons, only strains belonging to two genera, Sodiomyces and Thielavia, were turned
Isolation and Cultivation of Alkaliphiles
67
the alkaline pH is noticeably less than at near-neutral pH. Historically, alkaliphilic
eukaryotes from soda lakes have been studied in the most detail. Comprehensive
reviews of particular eukaryotes inhabiting African soda lakes (diatoms, green algae,
protozoa, invertebrates, fish, etc.) the reader can find in a valuable book edited by
Michael Schagerl [115], while eukaryotes from the other soda or alkaline lakes were
also the matter of exploring, e.g., picophytoplankton diversity in the Transylvanian
Basin (Romania) [116], fungi in the Mono Lake (USA) area [117], diatoms in Lake
Van [118], and assessment of the overall eukaryotic diversity in the three US
alkaline lakes plus a biofilm from the chimney at the Lost City hydrothermal vent
with a pH 11 [119]. The latter contemporary study has been fulfilled by the method
of massively parallel pyrotag sequencing targeting the V9 hypervariable region of
the 18S rRNA gene and aimed to compare eukaryotic communities living at acidic
(pH < 3) and alkaline (pH > 9) environments. It has been found that the number of
OTUs for alkaline lakes exceeds that for acid habitats, although the DNA derived
from allochthonous sources or environmental DNA (inactive or dead cells) may
contribute. It has been found that the most cosmopolitan OTU was a diatom
(Fragillariophyceae) that occurred both acidic and alkaline samples. Among the
shared alkaline OTUs were Frontonia and Lacrymaria (ciliates), Protaspa
(a cercozoan), a maxillopod metazoan OTU, a tracheophyte OTU and various
opisthokont OTUs including fungi. A unicellular chlorophyte Picocystis was expectedly found in the Mono Lake sample because this alga accounts for up to 50% of the
primary production there as it has been shown earlier [120].
In the 1980–1990s of the twentieth century, an interest of microbiologists to
alkaliphiles sparked the researchers to search for alkaliphilic fungi. Although the
ability of fungi to grow at pH 10 has been known for a long time [121], only a
targeted search for alkaliphilic fungi gave the first results in the beginning of the
1990s [122, 123]. The definition of alkaliphilicity at mycologists is slightly different
from that adopted by microbiologists. An earlier definition designated fungus which
could grow at pH up to 10, but not below pH 5–6, as alkaliphilic and those grew at
pH 10 and below pH 5–6 are regarded as alkalitolerant [122]. In a later definition, it
was proposed that fungal species be considered alkaliphilic provided their optimum
growth lies at pH above 8 and the acidic pH limit constraint 4–5 [124]. Among fungi
there are no species that would not grow at pH 7, so there are no fungal obligate
alkaliphiles in the “bacteriological sense.” The importance of using an alkaline
medium for the search for alkaliphilic fungi was already emphasized in the first
papers [122, 125]. However, the past decades of research have shown that the
diversity of, namely, alkaliphilic fungi by now, is not so large compared to
alkaliphilic bacteria, and the majority of species/genera of fungi/yeasts isolated at
pH 10 are often to be alkalitolerant [125–128].
This trend was recently confirmed in an extensive study, including morphological
and metagenomic analysis, on the search for alkaliphilic fungi from alkaline soils of
varying degrees of salinity sampled from Russia, Mongolia, Kazakhstan, Kenya,
Tanzania, and Armenia [124]. Among over 100 isolated strains assigning to various
taxons, only strains belonging to two genera, Sodiomyces and Thielavia, were turned
Isolation and Cultivation of Alkaliphiles
67