Abstract
Two psychrophilic bacterial samples were isolated from King George Island soil, in Antarctica. The phylogenetic analysis based on the 16S rRNA (rrs) gene led to the correlation with the closest related isolates as Sporosarcina aquimarina (99%) and Algoriphagus antarcticus (99%), with query coverage of 99% and 98%, respectively. The spent culture media from both isolates displayed proteolytic activities detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis containing gelatin as protein substrate. Under the employed conditions, S. aquimarina showed a 55 kDa protease with the best activity detected at pH 7.0 and at 27°C. A. antarcticus also showed a single extracellular protease, however its molecular mass was around 90kDa and its best activity was detected at pH 9.0 and at 37°C. The proteases from both isolates were inhibited by 1,10-phenanthroline and EDTA, two metalloprotease inhibitors. This is the first record of protease detection in both species, and our results may contribute to broaden the basic knowledge of proteases from the Antarctica environment and may help prospecting future biotechnological applications of these enzymes.
Highlights
The Earth has a considerable proportion of extremely cold environments, represented by the Antarctic and Artic regions, as well as cold regions, including the oceans, which cover around 3⁄4 of the Earth’sDue to the low complexity of the food chain and the low number of individuals and diversity, any change in the physicochemical conditions of this environment is quickly noticeable in the various trophic levels (Yergeau and Kowalchuk 2008).The great selective pressure exerted by the Antarctic environmental conditions determines either the survival, the death or the efficient adaptation of the organisms, such as that of extremophile microorganisms known as psychrophiles (Morita 1975)
The diversity of microorganisms inhabiting cold environments has been extensively investigated over the past few years with a focus on culture-independent techniques, but the information obtained by such methods may be complemented by the cultivation of such microorganisms (Casanueva et al 2010)
Gratia et al (2009) demonstrated that, after the initial screening to ascertain exoenzyme production in more than 1000 isolates collected from several cold environments (Antarctica, Kerguelen Island, Spitzberg, Siberia, Canada, Lapland and other deep seawater samples), over 100 isolates showed the ability to produce at least two of the abovementioned exoenzymes at 4°C
Summary
The Earth has a considerable proportion of extremely cold environments, represented by the Antarctic and Artic regions, as well as cold regions, including the oceans (usually 4–5°C below a depth of 1,000m), which cover around 3⁄4 of the Earth’sDue to the low complexity of the food chain and the low number of individuals and diversity, any change in the physicochemical conditions of this environment is quickly noticeable in the various trophic levels (Yergeau and Kowalchuk 2008).The great selective pressure exerted by the Antarctic environmental conditions determines either the survival, the death or the efficient adaptation of the organisms, such as that of extremophile microorganisms known as psychrophiles (Morita 1975). Psychrophilic enzymes are characterized by high catalytic efficiency in low temperatures, high level of thermolability and an increased structural flexibility in order to provide better access to the substrate; in this sense, the protein flexibility plays a critical role bestowing adaptability to cold (Thomas and Dieckmann 2002). Despite their usefulness in industrial and domestic processes (Feller and Gerday 2003), psychrophiles and their products are underutilized in biotechnology due to the thermolability of their enzymes and the cost of production and processing at low temperatures (Margesin and Feller 2010). Advances in the biotechnology enzymatic area, especially with psychrophilic enzymes, have led to a rapid growth in this field (Cavicchioli et al 2002), the study of proteolytic enzymes from Antarctica is an interesting theme for biotechnology (Feller and Gerday 2003)
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