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1.  Survival of Spacecraft-Associated Microorganisms under Simulated Martian UV Irradiation 
Applied and Environmental Microbiology  2005;71(12):8147-8156.
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.
doi:10.1128/AEM.71.12.8147-8156.2005
PMCID: PMC1317311  PMID: 16332797
2.  Species Differentiation of a Diverse Suite of Bacillus Spores by Mass Spectrometry-Based Protein Profiling 
In this study, we demonstrate the versatility of matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOFMS) protein profiling for the species differentiation of a diverse suite of Bacillus spores. MALDI-TOFMS protein profiles of 11 different strains of Bacillus spores, encompassing nine different species, were evaluated. Bacillus species selected for MALDI-TOFMS analysis represented the spore-forming bacterial diversity of typical class 100K clean room spacecraft assembly facilities. A one-step sample treatment and MALDI-TOFMS preparation were used to minimize the sample preparation time. A library of MALDI-TOFMS spectra was created from these nine Bacillus species, the most diverse protein profiling study of the genus reported to date. Linear correlation analysis was used to successfully differentiate the MALDI-TOFMS protein profiles from all strains evaluated in this study. The MALDI-TOFMS protein profiles were compared with 16S rDNA sequences for their bacterial systematics and molecular phylogenetic affiliations. The MALDI-TOFMS profiles were found to be complementary to the 16S rDNA analysis. Proteomic studies of Bacillus subtilis 168 were pursued to identify proteins represented by the biomarker peaks in the MALDI-TOFMS spectrum. Four small, acid-soluble proteins (A, B, C, and D), one DNA binding protein, hypothetical protein ymf J, and four proteins associated with the spore coat and spore coat formation (coat JB, coat F, coat T, and spoIVA) were identified. The ability to visualize higher-molecular-mass coat proteins (10 to 25 kDa) as well as smaller proteins (<10 kDa) with MALDI-TOFMS profiling is critical for the complete and effective species differentiation of the Bacillus genus.
doi:10.1128/AEM.70.1.475-482.2004
PMCID: PMC321296  PMID: 14711677

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