Metabolism and Biodegradation of Spacecraft Cleaning Reagents by Strains of Spacecraft-Associated Acinetobacter

Spacecraft assembly facilities are oligotrophic and low-humidity environments that possess a diverse, dynamic, and low abundant core microbiome; where the Acinetobacter are among the dominant members of the community. In this presentation, we will show that several spacecraft-associated Acinetobacter metabolize or biodegrade the spacecraft cleaning reagents of ethanol (ethyl alcohol), 2-propanol (isopropyl alcohol), and Kleenol 30 (floor detergent). Under ultra-minimal conditions (0.2x M9, 26 μM Fe ^{2+}), ethanol is a sole carbon source, while cultures expectedly did not grow solely on 2-propanol. Rather, cultivations on mixtures of ethanol and 2-propanol showed enhanced plate counts at mole ratios of ≤0.50. In support, enzymology experiments support a NAD ^{+}-dependent oxidation of ethanol and 2-propanol by a membrane-bound alcohol dehydrogenase. In the presence of Kleenol 30, GC-MS measurements on ultra-minimal cultures of Acinetobacter radioresistens 50v1 indicated (a) biodegradation of Kleenol 30 into products including ethylene glycol constituents, (b) the potential metabolism of decanoate (formed during incubation of Kleenol 30 in 0.2x M9), and (c) decreases in the abundances of several hydroxy- and ketoacids in the extracellular fraction. Further, under ultra-minimal conditions, and when using ethanol as a sole carbon source, A. radioresistens 50v1 also exhibits a remarkable extremotolerance towards hydrogen peroxide ( 10 ^{8} cfu/mL, 1.5-log loss, 10 mM H _{2}O _{2}). Thus, these combined results provide a plausible biochemical rationale to the microbial ecology dynamics of spacecraft-associated environments, as under oligotrophic-like conditions, spacecraft cleaning reagents may serve as carbon and/or energy sources, and support extremotolerance towards the cleanroom conditions.