Newcombe David A, Schuerger Andrew C, Benardini James N, Dickinson Danielle, Tanner Roger, Venkateswaran Kasthuri
Biotechnology and Planetary Protection Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
Appl Environ Microbiol. 2005 Dec;71(12):8147-56. doi: 10.1128/AEM.71.12.8147-8156.2005.
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.
从航天器表面和组装设施中回收的形成孢子的微生物被暴露于模拟火星紫外线辐射下。研究了UVA（315至400纳米）、UVA+B（280至400纳米）以及全紫外线光谱（200至400纳米）在预期照射火星表面的紫外线强度下对微生物存活的影响。使用16S rRNA基因测序鉴定了从包括“火星奥德赛”号、X - 2000（航空电子设备）和国际空间站等多个航天器表面及其组装设施中分离出的微生物物种。筛选了43株芽孢杆菌孢子株，在使用低压汞灯以254纳米波长进行1000 J m(-2) 的UVC辐射后，19株分离株显示出对UVC辐射（200至280纳米）具有抗性。从航天器相关表面分离出的芽孢杆菌属物种的孢子比标准剂量测定菌株枯草芽孢杆菌168更具抗性。此外，UVA+B辐射使存活孢子数量减少90%所需的暴露时间比全紫外线光谱减少90%所需的暴露时间长35倍，这证实了UVC是主要的杀菌波段。在所测试的芽孢杆菌属物种中，短小芽孢杆菌菌株的孢子对所有三个紫外线波段以及全光谱都表现出最大抗性。对模拟火星紫外线辐射的抗性具有菌株特异性；短小芽孢杆菌SAFR - 032表现出比所有其他测试菌株更强的抗性。在确定紫外线辐射的杀菌能力时，应考虑像短小芽孢杆菌SAFR - 032这样的生物体的分离以及该生物体（六倍）比标准剂量测定菌株更高的存活率。
