A thermophilic microorganism from Deception Island, Antarctica with a thermostable glutamate dehydrogenase activity

Abstract

Background: The Antarctic continent is a source of extreme microorganisms. Millions of years of isolation have produced unique biodiversity with adaptive responses to its extreme environment. Although the Antarctic climate is mainly cold, the presence of several geothermal sites, including thermal springs, fumaroles, hot soils and hydrother mal vents, provides ideal environments for the development of thermophilic and hyperthermophilic microorganisms. Their enzymes, called thermoenzymes, are the focus of interest in both academic and industrial research, mainly due to their high thermal activity and stability. Glutamate dehydrogenase, is an enzyme that plays a key role in the metab olism of carbon and nitrogen catalyzing reversibly the oxidative deamination of glutamate to alpha ketoglutarate and ammonium. It belongs to the family of oxidoreductases, is widely distributed and it has been highly regarded for use as biosensors, particularly for their specifcity and ability to operate in photochemical and electrochemical systems. However, the use of enzymes as biosensors is relatively problematic due to their instability to high temperatures, organic solvents and denaturing agents. The purpose of this study is to present the partial characterization of a ther mophilic microorganism isolated from Deception Island, Antarctica, that displays glutamate dehydrogenase activity. Results: In this work, we report the isolation of a thermophilic microorganism called PID15 from samples of Decep tion Island collected during the Antarctic Scientifc Expedition ECA 46. This microorganism is a thermophile that grows optimally at 50 °C and pH 8.0. Scanning electron microscopy shows rod cells of 2.0 to 8.0 µm of length. Phylo genetic analysis of 16S rRNA gene revealed that this microorganism is closely related to Bacillus gelatini. This microor ganism contains a thermostable glutamate dehydrogenase with optimal activity at pH 8.0 and temperatures for its activity from 37 to 50 °C, range of temperature of interest for biotechnological applications. This glutamate dehydro genase is a highly thermostable enzyme. Conclusion: This is the frst report of a microorganism from Antarctica containing a thermostable glutamate dehy drogenase that maintains its activity in a broad range of temperatures making it of potential interest for biotechno logical applications.