Space Microbiology

Taylor, Gerald R.

doi:10.1146/annurev.mi.28.100174.001005

Cited by 89 publications

(53 citation statements)

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“…Basic microbial characteristics, such as changes in cell growth characteristics during flight, have been repeatedly evaluated. Changes in cell density were reported in early studies, including the increased Salmonella enterica serovar Typhimurium culture densities during experiments aboard Biosatillite 2 compared to ground controls (95). Escherichia coli also displayed similar increased growth during flight in several experiments (16,57,103).…”

Section: Summary Of Results From Selected Spaceflight Experimentsmentioning

confidence: 62%

Microbial Responses to Microgravity and Other Low-Shear Environments

Nickerson

Ott

Wilson

et al. 2004

Microbiol Mol Biol Rev

314

348

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Microbial adaptation to environmental stimuli is essential for survival. While several of these stimuli have been studied in detail, recent studies have demonstrated an important role for a novel environmental parameter in which microgravity and the low fluid shear dynamics associated with microgravity globally regulate microbial gene expression, physiology, and pathogenesis. In addition to analyzing fundamental questions about microbial responses to spaceflight, these studies have demonstrated important applications for microbial responses to a ground-based, low-shear stress environment similar to that encountered during spaceflight. Moreover, the low-shear growth environment sensed by microbes during microgravity of spaceflight and during ground-based microgravity analogue culture is relevant to those encountered during their natural life cycles on Earth. While no mechanism has been clearly defined to explain how the mechanical force of fluid shear transmits intracellular signals to microbial cells at the molecular level, the fact that cross talk exists between microbial signal transduction systems holds intriguing possibilities that future studies might reveal common mechanotransduction themes between these systems and those used to sense and respond to low-shear stress and changes in gravitation forces. The study of microbial mechanotransduction may identify common conserved mechanisms used by cells to perceive changes in mechanical and/or physical forces, and it has the potential to provide valuable insight for understanding mechanosensing mechanisms in higher organisms. This review summarizes recent and future research trends aimed at understanding the dynamic effects of changes in the mechanical forces that occur in microgravity and other low-shear environments on a wide variety of important microbial parameters

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Section: Summary Of Results From Selected Spaceflight Experimentsmentioning

confidence: 62%

Microbial Responses to Microgravity and Other Low-Shear Environments

Nickerson

Ott

Wilson

et al. 2004

Microbiol Mol Biol Rev

314

348

View full text Add to dashboard Cite

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“…Spacecraft assembly facilities are oligotrophic extreme environments in which only the most resilient species survive the high-desiccation, lownutrient conditions, controlled air circulation, and the rigors of bioburden reduction (56, 57). The biological inventory of microorganisms on spacecraft has mostly been limited to isolation and identification using standard culture-based microbiological assays (44,48,53). However, culture-based microbiological assays likely underestimate the biological diversity present on spacecraft, as traditional culture techniques fail to capture more than 99.9% of present phylotypes (7).…”

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confidence: 99%

“…Recently, the simultaneous use of culture-dependent and culture-independent techniques (e.g., Limulus amoebocyte lysate assay [LAL], ATP bioluminescence assay, lipopolysaccharide-based microbial detection, and DNA-based PCR) have identified many nonculturable species (31,32,57). Known culturable bacteria recovered from spacecraft surfaces include, but are not limited to, species of Acinetobacter, Bacillus, Corynebacterium, Escherichia, Flavobacterium, Micrococcus, Pseudomonas, Serratia, Staphylococcus, and Streptococcus (44,53,57).After launch, spacecraft are exposed to interplanetary conditions of ultralow pressure (3 ϫ 10 Ϫ10 kPa), extreme desiccating conditions, fluctuating temperatures, solar UV irradiation, and ionizing radiation (22,44). Furthermore, upon landing, the conditions on the surface of Mars are not much improved over interplanetary space.…”

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confidence: 99%

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confidence: 99%

“…Two bacterial species, Escherichia coli and Serratia liquefaciens, were selected from over 30 prokaryotic species tested in preliminary experiments (5,45). Their selection was based on their common association with humans, recovery from robotic spacecraft and space-based human life support systems (44,53), and demonstrated replication at 2.5 kPa of total atmospheric pressure (5,45). Experiments were conducted on cell suspensions in liquid medium at combinations of low pressure, high salt concentrations, and low temperatures, and then with cells mixed into soils and exposed to simulated Mars conditions.…”

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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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