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Water is a critical commodity for spacecraft crews, requiring extreme conservation and reclamation strategies. In addition to suppression of the immune system in spaceflight, enhancement of bacterial growth and antimicrobial resistance in weightlessness raise serious concerns regarding microbial contamination of water systems. Rapid methods are needed for monitoring water, both pre-flight and on orbit. We are developing techniques to enumerate specific, metabolically active bacteria that may threaten crew health or lead to water system deterioration. Our methods are directed at the detection of individual bacteria, rather than populations of bacteria, and we aim to determine the identity of the organism as well as its physiological state con-currently. Our objectives are to determine, in a single test, the total number of bacteria present in a water sample, if a specific strain of bacteria is present within the total population and if these bacteria are viable or dead.

NASA-Marshall Space Flight Center (MSFC) has an interest in an automated in-line monitor that can detect the presence of microbial contamination in recovered water. Ideally, this system should also be able to identify and enumerate the microbial contaminant. The Viable Microbial Monitor (VM2) is based on conductance microbiology which depends on the well documented ability of microorganisms to change the electrochemical properties of their growth medium during incubation. The VM2 is intended for the rapid detection of bacterial or fungal contamination in water and other samples. From October 1992 to July 1993, NASA-MSFC sponsored a Microbial In-line Monitor (MIM) study to evaluate the VM2 for its ability to detect ten microorganism species (9 bacteria and 1 yeast) recovered from Water Recovery Tests (WRT) conducted at MSFC. These WRT isolates may represent the microbes that have potential to contaminate a water recovery system.

Early detection of microbial contaminants in reclaimed water was investigated using conductivity measurements of cultured samples. Culture data were obtained by using conductivity electronics and a personal computer equipped with an analog-digital converter and multiplexer. The software was programmed to monitor 54 cultures. The cultures were incubated for up to 48 hours at 35°C. The real-time conductivity data obtained from these cultured samples produces curves comprised of multiple data points over time. Using laboratory cultures for conductivity measurements, growth was detected within 12-24 hours with inocula in the range of less than 100 to 105 colony forming units per ml (CFU/ml). Detection times ranged from 20-35 hours for reclaimed water samples, and bacteria in untreated waste-waters were detected in 2-15 hours.

Long-term space flight missions will require high quality water to lessen the risk of crew infections and system deterioration. In water systems on earth, biofilms contribute to loss of water quality, causing corrosion, increased flow resistance and reduced heat transfer. Some bacteria grow more rapidly and become less susceptible to antimicrobial agents under conditions of microgravity, and humans may have weakened immunity with prolonged space flight. This study aimed to determine the effects of spaceflight and microgravity on biofilm formation by Burkholderia cepacia in water and microbial control by iodine. The results showed that B. cepacia formed biofilms when incubated in microgravity and in ground controls. Compared to rich medium or water, biofilms developed at similar densities in iodinated water.