neutralophiles are evolved to function often around neutrality, the high pH of
alkaline habitats can disrupt their activity and stability, which potentially starve
the cell to death. Thus, one of the challenges in colonizing high pH habitats is to have
extracellular products that are efficient and operationally stable at elevated pH.
Another important high pH environment challenge is related to nutrient availability. The bioavailability of some nutrients can be affected by the pH of the
environment. Some nutrients become less available at high pH. However, since
the genesis and chemistry of alkaline environments are different, the scarcity of
nutrients could also vary from habitat to habitat. The scarcity problem in some soda
lakes is mentioned here as an example. Nutrients such as P, Ca, Mg, Fe, etc. are less
available in soda lakes [41, 42]. These substances either due to geological reasons or
reactions with other constituents of the lakes form insoluble precipitates which
severely diminish the bioavailability. However, these nutrients are important for
normal metabolic process. For instance, several enzymes require metal ions such as
Ca, Mg, and Fe for activity and/or stability [43]. Thus, the scarcity of these metals
can severely impair the function of the enzymes and adversely affect the metabolic
processes. The malfunctioning of metabolic processes can compromise cellular
activities which can lead to survival deterioration. Thus, colonization of high pH
habitats requires adaptive solutions to evade challenges related to poor nutrient
availability.
What has been described in the above are some of the important challenges of life
in alkaline environments, challenges that neutralophiles can face in high pH habitats.
Probably, solving these challenges was the key adaptive evolution of alkaliphiles
which allowed them to flourish in high pH environments. Below, the adaptive
strategies deployed by alkaliphiles to circumvent these grand challenges of alkaline
environments are discussed.
3 Adaptation of Alkaliphiles: Circumventing
the Challenges of Alkalinity
Often, organisms colonizing extreme habitats have unique features that allow them
not only to survive but also thrive in it. As discussed above, alkaline environments
are bundled with tough challenges, and yet it is home for richly diverse group of
organisms. The ability of lavishly growing at punishingly high pH in which
neutralophiles cannot even survive for a while indicates the unique adaptive strategies deployed by alkaliphiles. Unraveling the secret of high pH adaptation of
alkaliphiles has been the subject of several studies for decades. These studies have
contributed to our knowledge of high pH adaptations of organisms. An effort is
made here to summarize the important findings that depict the remarkable high pH
adaptation mechanisms of alkaliphiles.
92
G. Mamo
alkaline habitats can disrupt their activity and stability, which potentially starve
the cell to death. Thus, one of the challenges in colonizing high pH habitats is to have
extracellular products that are efficient and operationally stable at elevated pH.
Another important high pH environment challenge is related to nutrient availability. The bioavailability of some nutrients can be affected by the pH of the
environment. Some nutrients become less available at high pH. However, since
the genesis and chemistry of alkaline environments are different, the scarcity of
nutrients could also vary from habitat to habitat. The scarcity problem in some soda
lakes is mentioned here as an example. Nutrients such as P, Ca, Mg, Fe, etc. are less
available in soda lakes [41, 42]. These substances either due to geological reasons or
reactions with other constituents of the lakes form insoluble precipitates which
severely diminish the bioavailability. However, these nutrients are important for
normal metabolic process. For instance, several enzymes require metal ions such as
Ca, Mg, and Fe for activity and/or stability [43]. Thus, the scarcity of these metals
can severely impair the function of the enzymes and adversely affect the metabolic
processes. The malfunctioning of metabolic processes can compromise cellular
activities which can lead to survival deterioration. Thus, colonization of high pH
habitats requires adaptive solutions to evade challenges related to poor nutrient
availability.
What has been described in the above are some of the important challenges of life
in alkaline environments, challenges that neutralophiles can face in high pH habitats.
Probably, solving these challenges was the key adaptive evolution of alkaliphiles
which allowed them to flourish in high pH environments. Below, the adaptive
strategies deployed by alkaliphiles to circumvent these grand challenges of alkaline
environments are discussed.
3 Adaptation of Alkaliphiles: Circumventing
the Challenges of Alkalinity
Often, organisms colonizing extreme habitats have unique features that allow them
not only to survive but also thrive in it. As discussed above, alkaline environments
are bundled with tough challenges, and yet it is home for richly diverse group of
organisms. The ability of lavishly growing at punishingly high pH in which
neutralophiles cannot even survive for a while indicates the unique adaptive strategies deployed by alkaliphiles. Unraveling the secret of high pH adaptation of
alkaliphiles has been the subject of several studies for decades. These studies have
contributed to our knowledge of high pH adaptations of organisms. An effort is
made here to summarize the important findings that depict the remarkable high pH
adaptation mechanisms of alkaliphiles.
92
G. Mamo