3 Alkaliphiles
Alkaliphiles are one of the most important groups of extremophiles which are adapted
to thrive in high pH environments that are often lethal to other forms of life. These
organisms grow optimally at or above pH 9, and the most extreme strains can grow
lavishly as high as at pH 13.5 [4]. Alkaliphiles are believed to be the earliest life forms
on earth which originated billions of years ago in deep-ocean alkaline hydrothermal
vent systems [51, 52]. Today, alkaliphiles thrive in many geographical locations
across the planet, both in natural and manmade alkaline environments. Alkaline
soda lakes, soda deserts, and saline soda soils are the most important ecological niches
from which the largest number of alkaliphiles is isolated. Other natural habitats in
which alkaliphiles flourish include the alkaline serpentine lakes, oceanic bodies, ikaite
tufa columns, and alkaline hydrothermal vents. There are also a range of highly
alkaline anthropogenic driven environments such as drainages, lakes, and ponds
associated, among others, with steel, soda, and bauxite processing sites. Moreover,
alkaliphiles have also been isolated from neutral environments [53]. The isolation of
alkaliphiles from a range of alkaline and non-alkaline habitats indicates that these
organisms are quite common and are ecologically important. The isolation and
cultivation of alkaliphiles are discussed in detail in this volume (see [54]).
These fascinating organisms evolved structural and functional adaptive features
to thrive in the extreme alkaline environments, in which other organisms may die
instantly. Understanding the genetic makeups that are responsible for these adaptions is an interest to both applied and basic research (see [55]). In line with this, the
genome of several alkaliphiles has been sequenced and analyzed [56–58]. The
knowledge generated from genome and gene sequencing not only helps to unravel
the mechanism of high pH adaptations but also helps to tap the potential of these
organisms in biotechnological applications. Like other extremophiles, the great
majority of alkaliphiles are unculturable [59], and hence, direct isolation and screening of these microbes is limited. However, advances in molecular and computational
biology such as bioinformatics, genomics, data mining, sequencing, metagenomics,
cloning, and heterologous expression gave the possibility of utilizing these
unculturable alkaliphiles in various biotechnological applications. Moreover, the
breakthroughs in these disciplines together with the integrative approach may lead
to the discovery of alkaliphiles’ genetic blueprints for high pH adaptations and
capabilities in producing novel biotechnologically important substances.
Genetic, physiological, and biochemical studies revealed that alkaliphiles deploy
several intriguing strategies to thrive in their extreme habitats. Some of the most
important adaptations are shown in Fig. 2. These adaptive features not only allow
these organisms to flourish in the high pH environments but also make alkaliphiles
the most efficient ATP producers as well as fastest and denser growers compared to
their non-alkaliphile counterparts (see [60]). Most of the adaptive features of
alkaliphiles are of great importance in biotechnology. Acid production, efficient
siderophores, highly anionic cell surface, alkaline active enzymes, etc. are high pH
adaptations of alkaliphiles which are useful in various applications.
Alkaliphiles: The Versatile Tools in Biotechnology
9
Alkaliphiles are one of the most important groups of extremophiles which are adapted
to thrive in high pH environments that are often lethal to other forms of life. These
organisms grow optimally at or above pH 9, and the most extreme strains can grow
lavishly as high as at pH 13.5 [4]. Alkaliphiles are believed to be the earliest life forms
on earth which originated billions of years ago in deep-ocean alkaline hydrothermal
vent systems [51, 52]. Today, alkaliphiles thrive in many geographical locations
across the planet, both in natural and manmade alkaline environments. Alkaline
soda lakes, soda deserts, and saline soda soils are the most important ecological niches
from which the largest number of alkaliphiles is isolated. Other natural habitats in
which alkaliphiles flourish include the alkaline serpentine lakes, oceanic bodies, ikaite
tufa columns, and alkaline hydrothermal vents. There are also a range of highly
alkaline anthropogenic driven environments such as drainages, lakes, and ponds
associated, among others, with steel, soda, and bauxite processing sites. Moreover,
alkaliphiles have also been isolated from neutral environments [53]. The isolation of
alkaliphiles from a range of alkaline and non-alkaline habitats indicates that these
organisms are quite common and are ecologically important. The isolation and
cultivation of alkaliphiles are discussed in detail in this volume (see [54]).
These fascinating organisms evolved structural and functional adaptive features
to thrive in the extreme alkaline environments, in which other organisms may die
instantly. Understanding the genetic makeups that are responsible for these adaptions is an interest to both applied and basic research (see [55]). In line with this, the
genome of several alkaliphiles has been sequenced and analyzed [56–58]. The
knowledge generated from genome and gene sequencing not only helps to unravel
the mechanism of high pH adaptations but also helps to tap the potential of these
organisms in biotechnological applications. Like other extremophiles, the great
majority of alkaliphiles are unculturable [59], and hence, direct isolation and screening of these microbes is limited. However, advances in molecular and computational
biology such as bioinformatics, genomics, data mining, sequencing, metagenomics,
cloning, and heterologous expression gave the possibility of utilizing these
unculturable alkaliphiles in various biotechnological applications. Moreover, the
breakthroughs in these disciplines together with the integrative approach may lead
to the discovery of alkaliphiles’ genetic blueprints for high pH adaptations and
capabilities in producing novel biotechnologically important substances.
Genetic, physiological, and biochemical studies revealed that alkaliphiles deploy
several intriguing strategies to thrive in their extreme habitats. Some of the most
important adaptations are shown in Fig. 2. These adaptive features not only allow
these organisms to flourish in the high pH environments but also make alkaliphiles
the most efficient ATP producers as well as fastest and denser growers compared to
their non-alkaliphile counterparts (see [60]). Most of the adaptive features of
alkaliphiles are of great importance in biotechnology. Acid production, efficient
siderophores, highly anionic cell surface, alkaline active enzymes, etc. are high pH
adaptations of alkaliphiles which are useful in various applications.
Alkaliphiles: The Versatile Tools in Biotechnology
9