Preventing the Forward Contamination of Mars (2006) / Chapter Skim
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6 Advances in Technologies for Life Detection and Bioburden Reduction
6 Advances in Technologies for Life Detection and Bioburden Reduction
Pages 91-104
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From page 91... ...
.2 EXAMPLES OF METHODS FOR ASSESSING TOTAL VIABLE CELL COUNT Previously, a major obstacle to detecting and identifying microorganisms has been the limited capabilities of the available methodologies. Such microorganisms are of microscopic size and have relatively few morphological differences, and so detecting them and distinguishing individual taxa usually required the isolation and growth of microorganisms in the laboratory as pure cultures for metabolic and physiological investigations.
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From page 92... ...
, may not be well correlated with the counts of spore-forming bacteria on spacecraft. New rapid and less expensive methods that provide more accurate estimates of total viable bioburden, and that do not require growth of microorganisms in the laboratory, are described below.
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From page 93... ...
The technology is not useful for detection of archaean or eukaryan microorganisms and therefore is not effective in detecting total bioburden. A portable instrument that can produce results in near-real time is currently under development.
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From page 94... ...
The application of these techniques and others to planetary protection will require the development of a standard certification process that can calibrate the relationship between biomarker levels and bioburden as measured in terms of numbers and kinds of organisms. EXAMPLES OF METHODS FOR ESTIMATING BIODIVERSITY Measurement of the number of microbial cells on a spacecraft provides a first estimate of total bioburden, but additional information is needed if planetary protection requirements are to be sensitive to organism type.
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From page 95... ...
The molecular approach has been instrumental in revealing the diversity of and identifying novel microorganisms from a wide range of environments such as thermal springs (Reysenbach et al., 1994) , the South Pole (Carpenter et al., 2000)
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From page 96... ...
96 PREVENTING THE FORWARD CONTAMINATION OF MARS BOX 6.1 The Polymerase Chain Reaction Before a cell can divide, it must make an identical copy of all of the genetic information encoded within its DNA. Each daughter cell must inherit all of the original genes after the process of DNA replication, which is mediated by the enzyme called DNA polymerase.
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From page 97... ...
ADVANCES IN TECHNOLOGIES FOR LIFE DETECTION AND BIOBURDEN REDUCTION 97 FIGURE 6.1.1 Schematic representation of the successive splitting and copying of nucleic acid molecules in the polymerase chain reaction. SOURCE: Reprinted from Mullis and Faloona (1987)
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From page 98... ...
Denaturing Gradient Gel Electrophoresis Denaturing gradient gel electrophoresis (DGGE) is a highly sensitive and rapid technique often used to detect temporal and spatial shifts in microbial diversity.
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From page 99... ...
However, hardware can be designed for sterilization, albeit at greater cost, as long as the problem is approached at the onset of design. Incorporating planetary protection into future Mars mission programs at the earliest stages of design would give engineers a selection of effective bioburden reduction tools.18 The design phase of the Viking mission considered planetary protection requirements and supported investigations of heat sterilization to reduce total bioburden.
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From page 100... ...
Current bioburden reduction programs for spacecraft use no prequalification criteria for the selection of hardware, due to the added cost to the mission of conducting prequalification studies. Consequently, any bioburden reduction techniques beyond physical cleaning and environmental control should be evaluated to determine materials compatibility issues.
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From page 101... ...
ADVANCES IN TECHNOLOGIES FOR LIFE DETECTION AND BIOBURDEN REDUCTION 101 be a more feasible approach than gamma sterilization, because gamma sterilizers approach the size of a small building, whereas electron-beam sterilizers can fit in a typical laboratory room. Ambient-Temperature Sterilization Ethylene Oxide (EO)
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From page 102... ...
The next step is to assess these methods with respect to NASA planetary protection guidelines, evaluate their efficacy in comparison to current spore and culture methods, determine the optimal methodological approach for updating planetary protection requirements, and develop a defined standard certification process that will allow engineers and planetary protection officers to implement these advances as early in the mission development process as possible. Ultimately, the use of advanced detection methods to identify the potential bioburden may lead to bioburden reduction techniques that are targeted at groups of organisms of specific concern for planetary protection.
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From page 103... ...
1998. Perennial Antarctic lake ice: An oasis for life in a polar desert.
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From page 104... ...
1994. Phylogenetic analysis of the hyperthermophilic pink filament community in Octopus Spring, Yellowstone National Park.
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