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Drinking water aboard spacecraft and on earth must be monitored to ensure that harmful bacteria are absent. NASA needs rapid methods for this purpose, to avoid possible launch delays and limit potential water-related health risks aboard spacecraft on orbit. Determination of bacterial viability after exposure to disinfection has significant health importance since oxidatively injured pathogenic bacteria have been shown to retain their virulence. This problem is compounded by the observation that injured bacteria are recovered at significantly lower frequencies using standard agar plate assays, leading to an underestimation of infection risks. Escherichia coli O157:H7 was exposed to 0.5 ppm free chlorine, retained on membrane filters and tested for physiological activity using a variety of assays.

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.

Experiments were done to examine the sensitivity of various waterborne bacteria from iodinated systems to iodine, and their subsequent recovery and growth, because this halogen is used as a disinfectant in potable water systems on US manned space vehicles. A Pseudomonas aeruginosa isolated from a commercial iodine product was least sensitive when grown in reagent-grade water or phosphate buffered water (PBW) and most sensitive when cultivated on mineral salts medium supplemented with low levels of glucose and glutamate or Brain Heart Infusion (BHI) broth. However, a P. cepacia strain was most sensitive when grown on BHI broth. Isolates from an iodinated potable water system were less sensitive to iodine than Ps-4 while a clinical isolate exhibited intermediate sensitivity. Bacteria including Ps-4 generally recovered and grew in PBW at greater rates than uniodinated controls.

A number of microbiological issues are of critical importance to crew health and system performance in spacecraft water systems. This presentation will review an array of these concerns which include factors that influence water treatment and disinfection in spaceflight such as biofilm formation and the physiological responses of bacteria in clean water systems. Factors associated with spaceflight like aerosol formation under conditions of microgravity will also be discussed within the context of airborne infections such as Legionellosis. Finally, a spectrum of analytical approaches will be reviewed to provide an evaluation of methodological alternatives that have been suggested or used to detect microorganisms of interest in water systems. These range from classical approaches employing colony formation on specific microbiological growth media to direct (i.e. microscopic) and indirect (e.g. electrochemical) methods as well as the use of molecular approaches and gene probes.