Turk J Biol 26 (2002) 181-191 © TUBITAK

Alkaliphilic Micro-organisms and Habitats

Zeynep ULUKANLI

Kafkas University, Faculty of Arts and Science, Department of Biology, Kars - TURKEY

Metin DIĞRAK

Kahramanmaraş Sütçü İmain University, Faculty of Arts and Science, Department of Biology, Kahramanmarat- TURKEY

Received: 25.06.2001

Abstract: Alkaline environments are typical extreme environments which include naturally occurring soda lakes, deserts, soils and artificially occurring industrial-derived waters. Micro-organisms that occupy extreme pH environments have resulted in the definition of an unusual group, termed alkaliphiles, In this review, the current status of the biodiversity of alkaliphilic micro-organisms in various environments and aspects of their biotechnological potential are summarised briefly.

Key Words: Alkaliphiles, extreme environments, soda lakes, extremophiles, microbial ecology

Alkaline Environments

The most concentrated and widespread occurrences of organisms are generally observed in “moderate” environments. It has also been known that there are “extreme’ environments on earth which were thought to prevent the existence of life (1). In these habitats, environmental conditions such as pH, temperature and salinity concentrations are extremely high or low. Extreme environments are populated by groups of organisms that are specifically adapted to these particular conditions and these types of extreme micro-organisms are Usually referred to as alkaliphiles, halophiles, thermophiles and acidophiles, reflecting the particular type of extreme environment which they inhabit (1). In this review, the condition of high pH, which occurs in nature naturally or artificially, is the basis of the extreme environment which will be considered, and such environments are referred to as alkaline environments. The data presented in this short review are not intended to be exhaustive, but seek to give an indication of the complexity and diversity of alkaline biotopes.

The major goal of microbial ecology is to understand microbial diversity in natural habitats; therefore, knowledge of both micro-organisms and habitats is essential. Hypersaline waters can be classified into two groupings: the first, thalassohaline waters derived from the evaporation of seawater and the second is athalassohaline waters largely derived from the solution of evaporative deposits (2,3). The distribution and abundance of a specific type of extreme environments is very important for the degree of specia!isation of the biota. If one type of environment is common in the biosphere, has a wide geographical distribution and possesses a certain constancy in its characteristics throughout geological periods, one can presume that a long and complex evolutionary process could have taken place. In the case of hypersalinity, it is clear that the above considerations apply to thalassohaline waters. Alkaline-carbonate lakes also possibly conform to these conditions (3). In describing the distribution and abundance of alkaliphilic micro-organisms, it is essential

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