Bauermeister Anja, Mahnert Alexander, Auerbach Anna, Böker Alexander, Flier Niwin, Weber Christina, Probst Alexander J, Moissl-Eichinger Christine, Haberer Klaus
Compliance Advice and Services in Microbiology GmbH, Cologne, Germany.
Department for Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany.
PLoS One. 2014 Apr 15;9(4):e94265. doi: 10.1371/journal.pone.0094265. eCollection 2014.
Bioburden encapsulated in spacecraft polymers (such as adhesives and coatings) poses a potential risk to jeopardize scientific exploration of other celestial bodies. This is particularly critical for spacecraft components intended for hard landing. So far, it remained unclear if polymers are indeed a source of microbial contamination. In addition, data with respect to survival of microbes during the embedding/polymerization process are sparse. In this study we developed testing strategies to quantitatively examine encapsulated bioburden in five different polymers used frequently and in large quantities on spaceflight hardware. As quantitative extraction of the bioburden from polymerized (solid) materials did not prove feasible, contaminants were extracted from uncured precursors. Cultivation-based analyses revealed <0.1-2.5 colony forming units (cfu) per cm3 polymer, whereas quantitative PCR-based detection of contaminants indicated considerably higher values, despite low DNA extraction efficiency. Results obtained from this approach reflect the most conservative proxy for encapsulated bioburden, as they give the maximum bioburden of the polymers irrespective of any additional physical and chemical stress occurring during polymerization. To address the latter issue, we deployed an embedding model to elucidate and monitor the physiological status of embedded Bacillus safensis spores in a cured polymer. Staining approaches using AlexaFluor succinimidyl ester 488 (AF488), propidium monoazide (PMA), CTC (5-cyano-2,3-diotolyl tetrazolium chloride) demonstrated that embedded spores retained integrity, germination and cultivation ability even after polymerization of the adhesive Scotch-Weld 2216 B/A. Using the methods presented here, we were able to estimate the worst case contribution of encapsulated bioburden in different polymers to the bioburden of spacecraft. We demonstrated that spores were not affected by polymerization processes. Besides Planetary Protection considerations, our results could prove useful for the manufacturing of food packaging, pharmacy industry and implant technology.
封装在航天器聚合物（如粘合剂和涂层）中的生物负载对其他天体的科学探索构成了潜在风险。这对于打算进行硬着陆的航天器部件尤为关键。到目前为止，聚合物是否确实是微生物污染的来源尚不清楚。此外，关于微生物在嵌入/聚合过程中的存活数据很少。在本研究中，我们开发了测试策略，以定量检测在航天硬件中频繁大量使用的五种不同聚合物中的封装生物负载。由于从聚合（固体）材料中定量提取生物负载不可行，因此从未固化的前体中提取污染物。基于培养的分析表明，每立方厘米聚合物中有<0.1-2.5个菌落形成单位（cfu），而基于定量PCR的污染物检测显示的值要高得多，尽管DNA提取效率较低。通过这种方法获得的结果反映了封装生物负载的最保守指标，因为它们给出了聚合物的最大生物负载，而不考虑聚合过程中发生的任何额外物理和化学应力。为了解决后一个问题，我们采用了一个嵌入模型来阐明和监测固化聚合物中嵌入的安全芽孢杆菌孢子的生理状态。使用AlexaFluor琥珀酰亚胺酯488（AF488）、单叠氮化丙锭（PMA）、CTC（5-氰基-2,3-二对甲苯基四唑氯化物）的染色方法表明，即使在Scotch-Weld 2216 B/A粘合剂聚合后，嵌入的孢子仍保持完整性、发芽能力和培养能力。使用本文介绍的方法，我们能够估计不同聚合物中封装生物负载对航天器生物负载的最坏情况贡献。我们证明孢子不受聚合过程的影响。除了行星保护考虑外，我们的结果可能对食品包装、制药行业和植入技术的制造有用。
