In reference to the 9th Edition of the Ilídio Pinho Prize Foundation “Science at School”, entitled, in 2011, “Biology/ Earth and Life Sciences ”, a group of students and teachers from Escola Secundária D. Maria II– Braga, have developed, between January and May 2011, a project on “extremophile beings”. Its purpose is to allow high school students the possibility to study microorganisms that can survive under unfavorable conditions, compared to those of the so called “normal” life, in a laboratorial environment.
The collected data will enable students to develop Astrobiology studies, trying to extrapolate this data to other regions of the Solar System.
The investigation done, aimed at further studies in Astrobiology, trying to understand, not only the typology of the different life forms on Earth, under extreme conditions of diverse abiotic factors but, above all, to extrapolate their studies to similar situations that might exist in other regions of the Solar System.
After a period of bibliographical research work on this matter, the students realized that there is the possibility of existing on Mars, today as well as in the past, halophile beings and sulfur reducing bacteria. Therefore, in order to develop their experimental activities, they selected the hypothermal and sulfuric waters from two superficial water springs in the Vizela Thermal Park and the following microorganisms: Saccharomyces cerevisiae, a standard yeast, an halophile yeast, Debaryomyces hansenii, and a sulfur reducing bacteria, anaerobic, Desulfovibrio desulfuricans.
Practical activities consisted in the analysis of the pH values and temperature of the collected water samples, the analysis of the macro and micro morphological characteristics of the selected yeasts in both solid and liquid media, the analysis the of their fermenting abilities of some sugars, the search for microorganisms in the water samples, in liquid and solid media, and in the investigation of the growth of the selected microorganisms in the same samples.
The physical and chemical study of the water samples focused on three physical and chemical parameters, namely smell and color (organoleptic), temperature, and pH. The first analysis was done “in loco”, when the samples of water were collected. Later on, in the lab, a group of seven students planned and carried out the analyses of the water by using temperature sensors, pH meter (pHmetro) and calorimetric indicators of acid base. From the results obtained, they could conclude that, at the temperature of the samples, its character was basic, exceeding pH 9. The use of indicators confirmed the chemical character of the water. They could also observe the variation of pH, depending on the temperature of the water.
The studies that were carried out to acknowledge the macro morphological characteristics in solid medium, S.cerevisiae and D. hansenii colonies, and micro morphological in the liquid medium of the respective cells, important to conduct and confirm diagnostics in taxonomical terms, showed that these characteristics depend on the composition of the medium.
The observation of the fermentative ability of the yeasts selected for the substrates tested didn’t show any significant differences.
The search for microorganisms in solid medium, in the collected water samples, allowed the observation of a significant quantity and diversity of aerobic bacteria, which proved to be higher in the thermal water at the temperature of 38 degrees centigrade. The presence of thermophile microorganisms was detected in the liquid medium. Among them, negative Gram bacteria were identified.
Investigations carried out on the growth of the different microorganisms selected for this project, in the water samples, allowed the observation of very similar results. Therefore, for all, D. Desulfuricans, S. cerevisiae and D. hansenii, the growth was more significant when optimum culture substrate was added to the water samples, even in a small quantity (25%, v/v). On the other hand, studies on yeasts showed that, as the culture became richer in thermal water and poorer in Y.E.P.D., some changes occurred in their macro morphological characteristics. It hasn’t registered any changes according to water temperature. D. hansenii revealed macro morphological characteristics, both in liquid and solid media, different from S. cerevisiae, evidencing better growth than this last one, for lower concentrations of Y.E.P.B. The study of the micro morphological characteristics in M.O. has shown that the cells of these two yeasts are very similar.
This work has created the possibility to study halophile and thermophile micro organisms, able to use sulfur, which can survive under high conditions of salt, temperature and sulfur, making it possible, for this reason, their existence in other regions of the Universe. Through the same work, the students have enlarged their knowledge on extremophile organisms and also on the evidence of extra terrestrial life. Indeed, it is known, today, that there are oceans with high concentrations of salt on Jupiter’s Europa Moon. On the other hand, Robots Spirit and Opportunity have detected the presence of evaporitic sulfate deposits on Mars, and some direct and indirect evidence has also appeared on the presence of liquid water and living hyperthermophile beings. It is also believed that there is the possibility of sulfur reducing bacteria existing on Venus and on Jupiter’s Yo Moon. Therefore, the existence and proliferation of living beings under these conditions, on terrestrial ecosystems, can constitute evidence for the possibility of extraterrestrial microorganisms.
This investigation has lead to the relevance and very updated questions that may be a great contribution to the understanding of life forms with uncommon patterns and life conditions and to de knowledge and understanding of life forms that might exist, or might have existed in other extraterrestrial regions.

 

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Departamento de Biologia da Universidade do Minho