Environmental conditions in Antarctica are different from all other places of the planet. Although the Antarctic climate is mainly cold, it is far from being uniform. The Cenozoic period had seen constant volcanic activity in this continent, and it is possible to find steaming ground in some circumpolar islands, such as Deception Island [1].
Deception Island is one of the seven islands that constitute the South Shetland archipelago of the Antarctic continent (Fig. 1). This island is a stratovolcano with horseshoe-shaped due to the sinking of the central part of 17 km diameter. The volcano rises 1400 m from the seafloor to a maximum height of 540 m above sea level and lies on the expansion axis of the Bransfield rift, which separates the South Shetland Islands from the Antarctic Peninsula [2]. The age of this island is less than 780 Ka and was probably formed by the collapse of the upper part of an ancient composite volcano that probably became active. As a result of this volcanic activity, the island is composed mainly of andesite effusions, a pyroclastic rock. Although major volcanic eruptions occurred in 1967, 1969 and 1970, today the presence of geothermal volcanic activity is represented by fumaroles and hot soils [3].
The presence of a large number of fumaroles and other geothermal areas are characteristics that make the island interesting for the study of microorganisms, specifically thermophiles. One of the most predominant groups of bacteria found in geothermal soils in Antarctica belongs to the aerobic endospore forming Bacillus. So far, thermophilic bacteria found in these geothermal areas belong to the Bacillaceae family [1, 4].
Recently, studies using denaturing gradient gel electrophoresis (DGGE) using the 16S ribosomal gene were used to analyze bacterial diversity present in a soil sample taken from Fumarole Bay, Deception Island [5]. The study indicated the presence of bacteria from the genera Geobacillus, Bacillus, Brevibacillus, Thermus and uncultured sulphate reducing bacteria, some of them reported before in other Antarctic geothermal sites. Regarding Archaea, only few microorganisms have been described. These includes Thermococcus and Pyrococcus [6, 7].
Thermophiles and hyperthermophiles are source of novel enzymes which present biochemical characteristics that differ from their mesophilic counterparts. Therefore, they are currently being studied and have also been described from Antarctic microorganisms. These enzymes called thermoenzymes are focus of interest in both academic and industrial research, mainly due to their high thermal stability (resistance to inactivation at high temperatures) and optimal activity at high temperatures. These enzymes are adapted to function at growth conditions of the microorganism from where they come. The extreme temperature, pH, salinity, in many cases define the optimal conditions at which the enzymatic activity can be detected [8,9,10]. They also play an important role in the growing biotech market, with applications in agriculture, biomedicine and industry, among others, due to their thermal stability which facilitate its use in processes requiring high temperatures.
One of the enzymes of high scientific and applied interest is glutamate dehydrogenase (GDH). GDH plays a major role in the metabolism of carbon and nitrogen [11]. It belongs to the family of oxidoreductases and is widely distributed in Eukarya, Bacteria and Archaea. Its function is to reversibly catalyze oxidative deamination of glutamate to alpha-ketoglutarate and ammonium [10, 12]. In applications, oxidoreductases like GDH have been highly regarded for their specificity and ability to operate in photochemical and electrochemical systems as biosensors. However, their use has been limited due to the instability at high temperatures, in the presence of organic solvents and denaturing agents [13].
Many commercial kits for the quantification of ammonium and glutamate in biological fluids or food products are based on redox reaction of NAD(P)+ [14, 15].
In the food and wine industry, the amount of ammonia can be determined using GDH. The enzyme allows to determine the degree of decomposition of foods, quantifying the concentration of ammonia produced due to the bacterial degradation of proteins, peptides and amino acids [16]. However, currently the bovine GDH used in this kit lacks the stability required for its use at room temperature and for long term storage (Roche 1996–2010).
In this work, we report the isolation of a new thermophilic microorganism called PID15 from samples of Deception Island collected during the Antarctic Scientific Expedition ECA 46, which has a glutamate dehydrogenase able to work in a range of temperatures from 37 to 50 °C and at pH from neutral to slightly alkaline showing properties for potential biotechnological applications.