Eukaryotic organisms in extreme acidic environments, the río tinto case.

Angeles Aguilera

doi:10.3390/life3030363

Abstract

A major issue in microbial ecology is to identify the limits of life for growth and survival, and to understand the molecular mechanisms that define these limits. Thus, interest in the biodiversity and ecology of extreme environments has grown in recent years for several reasons. Some are basic and revolve around the idea that extreme environments are believed to reflect early Earth conditions. Others are related to the biotechnological potential of extremophiles. In this regard, the study of extremely acidic environments has become increasingly important since environmental acidity is often caused by microbial activity. Highly acidic environments are relatively scarce worldwide and are generally associated with volcanic activity or mining operations. For most acidic environments, low pH facilitates metal solubility, and therefore acidic waters tend to have high concentrations of heavy metals. However, highly acidic environments are usually inhabited by acidophilic and acidotolerant eukaryotic microorganisms such as algae, amoebas, ciliates, heliozoan and rotifers, not to mention filamentous fungi and yeasts. Here, we review the general trends concerning the diversity and ecophysiology of eukaryotic acidophilic microorganims, as well as summarize our latest results on this topic in one of the largest extreme acidic rivers, Río Tinto (SW, Spain).

Highlights

Our ongoing exploration of Earth has led to continued discoveries of life in environments that have been previously considered uninhabitable
Using proteomic analysis of global expression patterns of cellular soluble proteins in an acidophilic strain of Chlamydomonas sp. we found that several stress-related proteins are induced in the cells growing in natural river water, along with a complex battery of proteins involved in photosynthesis, primary and energy metabolism or motility [42]
Acidic habitats are rather peculiar because in most cases they are the product of metabolism of active chemolithotrophic microorganisms

Summary

Introduction

Our ongoing exploration of Earth has led to continued discoveries of life in environments that have been previously considered uninhabitable. Life has evolved strategies that allow it to survive even beyond the daunting physical and chemical limits to which it has adapted to grow. Organisms can assume forms that enable them to withstand freezing, complete desiccation, starvation, high levels of radiation exposure, and other physical or chemical challenges. Biochemical studies will reveal inherent features of biomolecules and biopolymers that define the physico-chemical limits of life under extreme conditions. Broadening our knowledge both of the range of environments on Earth that are inhabitable by microbes and of their adaptation to these habitats will be critical for understanding how life might have established itself and survived

Eukaryotic Extremophiles

Photosynthesis in Acidic Environments

Findings

Conclusions