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Survival of Spacecraft-Associated Microorganisms under Simulated Martian UV Irradiation

机译：模拟火星紫外线辐射下与航天器有关的微生物的存活

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Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA+B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m?2 of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA+B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined.
机译：从航天器表面和组装设施中回收的形成孢子的微生物暴露在模拟的火星紫外线辐射下。在预期会撞击火星表面的紫外线强度下，研究了UVA（315至400 nm），UVA + B（280至400 nm）和完整UV光谱（200至400 nm）对微生物存活的影响。使用16S rRNA基因测序鉴定了从包括Mars Odyssey，X-2000（航空电子设备）和国际空间站等几种航天器表面分离出的微生物，并确定了其组装设施。筛选了43个芽孢杆菌芽孢系，并且在使用低压汞灯暴露于254 nm的1,000 J m？2的UVC辐射后，有19个分离株显示出对UVC辐射的抵抗力（200至280 nm）。从航天器相关表面分离的芽孢杆菌物种的孢子比标准剂量菌株枯草芽孢杆菌168具有更高的抗性。此外，UVA + B辐射使活孢子数减少90％所需的暴露时间长35倍。比整个UV光谱所需的曝光时间要长，这证明UVC是主要的杀菌带宽。在测试的芽孢杆菌物种中，短芽孢杆菌菌株的孢子对所有三个紫外线带宽以及总光谱显示出最大的抵抗力。对模拟火星紫外线辐射的抵抗力是应变特异性的。短小芽孢杆菌SAFR-032表现出比所有其他测试菌株更高的抗性。确定紫外线辐照的卫生能力时，应考虑分离出短小芽孢杆菌SAFR-032等生物，并使其存活率（六倍）高于标准剂量菌株。

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