Abstract
Spacecraft assembly facilities are oligotrophic and low-humidity environments, which are routinely cleaned using alcohol wipes for benchtops and spacecraft materials, and alkaline detergents for floors. Despite these cleaning protocols, spacecraft assembly facilities possess a persistent, diverse, dynamic, and low abundant core microbiome, where the Acinetobacter are among the dominant members of the community. In this report, we 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 ultraminimal conditions. Using cultivation and stable isotope labeling studies, we show that ethanol is a sole carbon source when cultivating in 0.2 × M9 minimal medium containing 26 μM Fe(NH4)2(SO4)2. Although cultures expectedly did not grow solely on 2-propanol, cultivations on mixtures of ethanol and 2-propanol exhibited enhanced plate counts at mole ratios of ≤0.50. In support, enzymology experiments on cellular extracts were consistent with oxidation of ethanol and 2-propanol by a membrane-bound alcohol dehydrogenase. In the presence of Kleenol 30, untargeted metabolite profiling on ultraminimal cultures of Acinetobacter radioresistens 50v1 indicated (1) biodegradation of Kleenol 30 into products including ethylene glycols, (2) the potential metabolism of decanoate (formed during incubation of Kleenol 30 in 0.2 × M9), and (3) decreases in the abundances of several hydroxy- and ketoacids in the extracellular metabolome. In ultraminimal medium (when using ethanol as a sole carbon source), A. radioresistens 50v1 also exhibits a remarkable survival against hydrogen peroxide (∼1.5-log loss, ∼108 colony forming units (cfu)/mL, 10 mM H2O2), indicating a considerable tolerance toward oxidative stress under nutrient-restricted conditions. Together, these results suggest that the spacecraft cleaning reagents may (1) serve as nutrient sources under oligotrophic conditions and (2) sustain extremotolerances against the oxidative stresses associated with low-humidity environments. In perspective, this study provides a plausible biochemical rationale to the observed microbial ecology dynamics of spacecraft-associated environments.
Highlights
Spacecraft assembly, test, launch, and operational procedures that minimize the biological contamination of explored environments are critical to ensuring the integrity of future life-detection missions, and in mitigating irreversible impacts to any native biochemical states (Space Studies Board, 2000, 2006)
The tested strains included A. radioresistens 50v1, which was isolated from the surface of the preflight Mars Odyssey orbiter, and A. proteolyticus 2P01AA, A. johnsonii 2P08AA, A. johnsonii 2P07AA, A. oryzare 2P08MC, A. guillouiae 2P07PB, and A. guillouiae 2P07PC, which were isolated from the floor of the assembly facility for the Mars Phoenix lander
Our studies indicate that decanoate is biodegraded by A. radioresistens 50v1 (Fig. 5), with the results (Fig. 5B) suggesting concomitant increases in abundances of suberic acid, which along with acetyl-CoA would potentially be a metabolic product of o-oxidation of decanoate (Donoghue and Trudgill, 1975; Kunz and Weimer, 1983; Van Bogaert et al, 2011)
Summary
Spacecraft assembly, test, launch, and operational procedures that minimize the biological contamination of explored environments are critical to ensuring the integrity of future life-detection missions, and in mitigating irreversible impacts to any native biochemical states (Space Studies Board, 2000, 2006). The commonly used cleaning reagents for these purposes are ethanol (ethyl alcohol) and 2-propanol (isopropyl alcohol, isopropanol) for benchtops and spacecraft materials (Barengoltz, 1997; Benardini et al, 2014; Frick et al, 2014), and Kleenol 30 for the clean room floors (Vaishampayan et al, 2013; Benardini et al, 2014; Mahnert et al, 2015) Despite these practices, spacecraft assembly facilities possess a persistent, yet low abundant core microbiome (*101–102 colony forming units (cfu)/cm2, *0.2–300 spores/m2, *1–40 OTU/m2), with molecular genetics revealing a taxonomically diverse and dynamic microbial community (Venkateswaran et al, 2001; Moissl et al, 2007; Vaishampayan et al, 2010; La Duc et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
