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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.

To compare the disinfection susceptibility of mucoid and non-mucoid P. aeruginosa in relation to EPS production, cultures were grown to stationary phase in defined media with a high or low C/N ratio using glucose as carbon source. Cultures diluted with phosphate buffered water pH 7.2 were pretreated by vortexing, centrifuging, or blending with 10 mM EDTA in PBW before disinfection with iodine, chlorine or monochloramine. It is suggested that differences observed between disinfectants may be due to their reactivities with cell constituents or modes of action. EPS may play a significant role in bacterial resistance to iodine and other halogens, although susceptibility varies markedly in relation to nutrient status and sample treatment before disinfection.

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.

This study was done to quantify the sensitivity of bacteria to iodine under controlled laboratory conditions. When exposed to 1 mg/; I2 for 1 min, bacteria isolated from the Shuttle were more resistant than a P. aeruginosa isolated from a povidine-iodine solution. Cultures grown in rich media were more sensitive than those grown in low nutrient solutions. The P. aeruginosa and a P. cepacia isolated from the Shuttle were resuspended in PBW after exposure to iodine. Iodinated cells recovered better than uniodinated controls. Pseudomonads in biofilms developed on coupons of stainless steel were more resistant to iodine than cells suspended in buffered water. Although resistant bacteria may colonize spacecraft water systems, multiple treatment barriers should provide adequate control of these contaminants.