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Bacterial survival in Martian conditions
No full textWe shortly discuss the observable consequences of the two hypotheses about the origin of life on Earth and Mars: the Lithopanspermia (Mars to Earth or viceversa) and the origin from a unique progenitor, that for Earth is called LUCA (the LUCA hypothesis). To test the possibility that some lifeforms similar to the terrestrial ones may survive on Mars, we designed and built two simulators of Martian environments where to perform experiments with different bacterial strains: LISA and mini-LISA. Our LISA environmental chambers can reproduce the conditions of many Martian locations near the surface trough changes of temperature, pressure, UV fluence and atmospheric composition. Both simulators are open to collaboration with other laboratories interested in performing experiments on many kind of samples (biological, minerals, electronic) in situations similar to that of the red planet. Inside LISA we have studied the survival of several bacterial strains and endospores. We verified that the UV light is the major responsible of cell death. Neither the low temperature, nor the pressure, nor the desiccation or the atmospheric changes were effective in this sense. We found that some Bacillus strains have a particular capability to survive for some hours in Martian conditions without being screened by dust or other shields. We also simulated the coverage happening on a planet by dust transported by the winds, blowing on the samples a very small quantity of volcanic ash grains or red iron oxide particles. Samples covered by these dust grains have shown a high percentage of survival, indicating that under the surface dust, if life were to be present on Mars in the past, some bacteria colonies or cells could still be present
New approaches to the exploration: planet Mars and bacterial life
No full textPlanet Mars past environmental conditions were similar to the early Earth, but nowadays they are similar to those of a very cold desert, irradiated by intense solar UV light. However, some terrestrial lifeform showed the capability to adapt to very harsh environments, similar to the extreme condition of the Red Planet. In addition, recent discoveries of water in the Martian permafrost and of methane in the Martian atmosphere, have generated optimism regarding a potentially active subsurface Mars' biosphere. These findings increase the possibility of finding traces of life on a planet like Mars. However, before landing on Mars with dedicated biological experiments, it is necessary to understand the possibilities of finding life in the present Martian conditions. Finding a lifeform able to survive in Martian environment conditions may have a double meaning: increasing the hope of discovering extraterrestrial life and defining the limits for a terrestrial contamination of planet Mars. In this paper we present the Martian environment simulators LISA and mini-LISA, operating at the Astronomical Observatory of Padua, Italy. They have been designed to simulate the conditions on the surface of planet Mars (atmospheric pressure,0.6-0.9 kPa; temperature from -120 to 20 °C, Martian-like atmospheric composition and UV radiation). In particular, we describe the mini-LISA simulator, that allows to perform experiments with no time limits, by weekly refueling the liquid nitrogen reservoir. Various kind of experiments may be performed in the simulators, from inorganic chemistry to biological activity. They are offered as experimental facilities to groups interested in studying the processes that happen on the Martian surface or under its dust cover. *(see notes
Factors influencing the haematoporphyrin-sensitized photoinactivation of Candida albicans.
No full textDetermination of extracellular and intracellular-pH of Bacillus subtilis suspension under CO2 treatment
No full textIn this paper we consider the effect of the gas on the intracellular and extracellular pH of a saline solution of a test-microorganisms Bacillus subtilis. In particular the extracellular pH was determined theoretically by means of the Statistical Associated Fluid Theory equation of state (SAFT EOS, (1-4). It was demonstrated that CO2 under pressure dissolves into liquid phase and acidifies the medium down to 3 at 80 bar and 303.15 K. The cytoplasmatic pH was determined by means of a flow cytometry with the fluorescent probe 5(and 6-)-carboxyfluorescein ester (cFSE). The physiological suspension of cells with the addition of the probe was first exposed to high pressure CO2 for 5 minutes at different temperatures. The flow cytometry analysis indicated an intracellular depletion inside the cell caused by the action of CO2, down to 3, the depletion being dependent on inactivation ratio. The results demonstrate a strong influence between extracellular and intracellular pH, and lead to the conclusion that a strong reduction of the pH homeostasis of the cell can be claimed as one of the most probable cause of inactivation in CO2 pasteurization
High pressure CO2 inactivation of food: A multi-batch reactor system for inactivation kinetic determination.
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