Rapid inactivation of seven Bacillus spp. under simulated Mars UV irradiation☆

Schuerger, Andrew C.; Richards, Jeffrey T.; Newcombe, David; Venkateswaran, Kasthuri

doi:10.1016/j.icarus.2005.10.008

Cited by 95 publications

(119 citation statements)

References 35 publications

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“…In brief, soil samples were suspended in 50-ml sterile plastic centrifuge tubes containing 20 ml SDIW, sonicated for 4 min, vortexed for 2 min, and serially diluted, and 20 l of each dilution was pipetted into each of 16 wells of a 96-well plate preloaded with 180 l of mLB broth per well. The fully loaded 96-well dishes were incubated at 30°C for 24 h. The MPNs were estimated as described previously (47,50). Each treatment was performed in triplicate, and the experiment was conducted three times (n ϭ 9).…”

Section: Methodsmentioning

confidence: 99%

“…The MSC system can accurately simulate five key components of the surface environment of Mars, including (i) pressures down to 0.01 kPa, (ii) UV irradiation from 190 to 400 nm, (iii) dust loading in the atmosphere from optical depths of 0.1 (dust-free sky) to 3.5 (global dust storm), (iv) temperatures from Ϫ100 to 30°C (based on Viking and Mars Pathfinder data [18,28]), and (v) a Mars gas mix that included CO 2 (95.3%), N 2 (2.7%), Ar (1.6%), O 2 (0.13%), and H 2 O (0.03%) (based on Viking data [40]). The Mars UV irradiation system has been described previously (46,47,50). The UVC (200 to 280 nm), UVB (280 to 320 nm), UVA (320 to 400 nm), and total UV fluence rates used in the current study were 3.6, 6.2, 25.9, and 35.6 W m…”

Section: Methodsmentioning

confidence: 99%

“…UV irradiation, especially UVC photons (200 to 280 nm), may be the most biocidal of all factors to microbial survival on the martian surface (34,37,39,47,50,52). Microorganisms found on sun-exposed surfaces of spacecraft are killed off within a few tens of minutes of exposure; but if covered by as little as a few hundred micrometers of martian soil, significant protection is provided (11,34,47).…”

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confidence: 99%

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Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Berry

Jenkins

Schuerger

2010

Appl Environ Microbiol

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Escherichia coli and Serratia liquefaciens, two bacterial spacecraft contaminants known to replicate under low atmospheric pressures of 2.5 kPa, were tested for growth and survival under simulated Mars conditions. Environmental stresses of high salinity, low temperature, and low pressure were screened alone and in combination for effects on bacterial survival and replication, and then cells were tested in Mars analog soils under simulated Mars conditions. Survival and replication of E. coli and S. liquefaciens cells in liquid medium were evaluated for 7 days under low temperatures (5, 10, 20, or 30°C) with increasing concentrations (0, 5, 10, or 20%) of three salts (MgCl 2 , MgSO 4 , NaCl) reported to be present on the surface of Mars. Moderate to high growth rates were observed for E. coli and S. liquefaciens at 30 or 20°C and in solutions with 0 or 5% salts. In contrast, cell densities of both species generally did not increase above initial inoculum levels under the highest salt concentrations (10 and 20%) and the four temperatures tested, with the exception that moderately higher cell densities were observed for both species at 10% MgSO 4 maintained at 20 or 30°C. Growth rates of E. coli and S. liquefaciens in low salt concentrations were robust under all pressures (2.5, 10, or 101.3 kPa), exhibiting a general increase of up to 2.5 orders of magnitude above the initial inoculum levels of the assays. Vegetative E. coli cells were maintained in a Mars analog soil for 7 days under simulated Mars conditions that included temperatures between 20 and ؊50°C for a day/night diurnal period, UVC irradiation (200 to 280 nm) at 3.6 W m ؊2 for daytime operations (8 h), pressures held at a constant 0.71 kPa, and a gas composition that included the top five gases found in the martian atmosphere. Cell densities of E. coli failed to increase under simulated Mars conditions, and survival was reduced 1 to 2 orders of magnitude by the interactive effects of desiccation, UV irradiation, high salinity, and low pressure (in decreasing order of importance). Results suggest that E. coli may be able to survive, but not grow, in surficial soils on Mars.The search for extant life on Mars remains a stated goal of NASA's Mars Exploration Program and Astrobiology Institutes (13,17). Intrinsic within such a life detection strategy is a requirement to understand how terrestrial life might survive, replicate, and proliferate on Mars. To mitigate the risks of the forward contamination of Mars, the bioloads on spacecrafts targeted for landing must be reduced to low density and diversity (4, 7). Planetary protection guidelines are designed to prevent both the forward contamination of the martian surface and to ensure the scientific integrity of any deployed life detection experiments. To date, 12 spacecraft have landed or crashed onto the Mars surface as a result of U.S., Russian, and European space program missions, but it is currently unknown if terrestrial microorganisms typically found on spacecraft surfaces can grow and replicate under con...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Berry

Jenkins

Schuerger

2010

Appl Environ Microbiol

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“…The current martian surface environment is characterized by low temperatures, low atmospheric pressure, and consequent low availability of liquid water, and it is exceedingly hostile to the persistence of life (Horneck, 2000). The thin atmospheric layer offers only minimal shielding against solar UV (Patel et al, 2002), which would rapidly kill any exposed microorganisms (Schuerger et al, 2006) and photolyze organic molecules such as amino acids (ten Kate et al, 2005). This long-term UV flux is also expected to have produced a wind-dispersed layer of chemical oxidants on the surface (Zent and McKay, 1994;Yen et al, 2000).…”

Section: Sterilization Of Mars' Surfacementioning

confidence: 99%

Ionizing Radiation and Life

2011

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Ionizing radiation is a ubiquitous feature of the Cosmos, from exogenous cosmic rays (CR) to the intrinsic mineral radioactivity of a habitable world, and its influences on the emergence and persistence of life are wideranging and profound. Much attention has already been focused on the deleterious effects of ionizing radiation on organisms and the complex molecules of life, but ionizing radiation also performs many crucial functions in the generation of habitable planetary environments and the origins of life. This review surveys the role of CR and mineral radioactivity in star formation, generation of biogenic elements, and the synthesis of organic molecules and driving of prebiotic chemistry. Another major theme is the multiple layers of shielding of planetary surfaces from the flux of cosmic radiation and the various effects on a biosphere of violent but rare astrophysical events such as supernovae and gamma-ray bursts. The influences of CR can also be duplicitous, such as limiting the survival of surface life on Mars while potentially supporting a subsurface biosphere in the ocean of Europa. This review highlights the common thread that ionizing radiation forms between the disparate component disciplines of astrobiology.

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“…Important from an experimental point view, therefore, is the study of survival of terrestrial organisms under simulated extraterrestrial conditions and various conditions of stress [2]. For example, following this experimental approach, the survival of bacterial spores (e.g., Bacillus spores) under simulated martian environmental conditions (SMEC) has been reported [3,4] as well as their survival under extreme conditions of ultraviolet radiation [5,6], heavy ions [7], simulated Mars solar radiation [8][9][10][11], low-pressure plasma [12], microgravity [13], outer space [14,15], Martian atmospheric pressure and composition [16], space vacuum and ultraviolet irradiation [17], and the comparative effects of several stresses on vegetative cells and spores [18] as well as under the environmental conditions of Jupiter's moon, Europe [19]. Survival of other bacteria, including an acidophilic chemolithotroph isolated from the Rio Tinto (Spain) and belonging to the Acidithiobacillus genus and Deinococcus radiodurans has been studied under SMEC [20], as well as methanogens under conditions of extreme dryness [21].…”

Section: Introductionmentioning

confidence: 99%

Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications

Gómez¹,

Estébanez²

2016

Astrobiol Outreach

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The principal goal of astrobiology is the search for extraterrestrial life forms. A key aspect is the study of the ability of different kinds of terrestrial organisms to support simulated extraterrestrial environmental conditions. Mosses are multicellular green plants, poorly studied from an astrobiological perspective. In this paper, we report experimental results obtained using two species of moss, which demonstrate that both the spores of the moss Funaria hygrometrica as well as the desiccated vegetative gametophyte shoots of the moss Tortella squarrosa (=Pleurochaete squarrosa) were capable of resisting Simulated Martian Environmental Conditions (SMEC): Mars simulated atmospheric composition 99.9% CO 2 , and 0.6% H 2 O with a pressure of 7 mbars, -73 º C and UV irradiation of 30 mW cm -2 in a wavelength range of 200-400 nm under a limited short time of exposition of 2 hours. After being exposed to SMEC and then transferred to an appropriate growth medium, the F. hygrometrica spores germinated, producing typical gametophyte protonemal cells and leafy shoots. Likewise, detached leaves from SMEC-exposed gametophyte shoots of T. squarrosa retained the ability to produce new protonemata and shoots under suitable growth conditions. Furthermore, we studied the tolerance of these moss structures to a thermal stress of 100 °C for 1 h; in both cases the spores and shoots were capable of resisting this heat treatment. Our study using FT-Raman and FT-IR vibrational spectroscopy demonstrated that neither spores nor shoots apparently suffered significant damage in their biomolecular makeup after being subject to these stress treatments. The implications of these findings for the search of life on Mars are discussed.

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Rapid inactivation of seven Bacillus spp. under simulated Mars UV irradiation☆

Cited by 95 publications

References 35 publications

Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Ionizing Radiation and Life

Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications

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