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Applied and Environmental Microbiology, August 2009, p. 5202-5208, Vol. 75, No. 16
0099-2240/09/$08.00+0     doi:10.1128/AEM.00789-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Roles of Small, Acid-Soluble Spore Proteins and Core Water Content in Survival of Bacillus subtilis Spores Exposed to Environmental Solar UV Radiation{triangledown}

Ralf Moeller,1* Peter Setlow,2 Günther Reitz,1 and Wayne L. Nicholson3

German Aerospace Center, Institute of Aerospace Medicine, Radiation Biology Division, Cologne, Germany,1 Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut,2 Department of Microbiology and Cell Science, University of Florida, Space Life Sciences Laboratory, Kennedy Space Center, Florida3

Received 7 April 2009/ Accepted 15 June 2009

Spores of Bacillus subtilis contain a number of small, acid-soluble spore proteins (SASP) which comprise up to 20% of total spore core protein. The multiple {alpha}/β-type SASP have been shown to confer resistance to UV radiation, heat, peroxides, and other sporicidal treatments. In this study, SASP-defective mutants of B. subtilis and spores deficient in dacB, a mutation leading to an increased core water content, were used to study the relative contributions of SASP and increased core water content to spore resistance to germicidal 254-nm and simulated environmental UV exposure (280 to 400 nm, 290 to 400 nm, and 320 to 400 nm). Spores of strains carrying mutations in sspA, sspB, and both sspA and sspB (lacking the major SASP-{alpha} and/or SASP-β) were significantly more sensitive to 254-nm and all polychromatic UV exposures, whereas the UV resistance of spores of the sspE strain (lacking SASP-{gamma}) was essentially identical to that of the wild type. Spores of the dacB-defective strain were as resistant to 254-nm UV-C radiation as wild-type spores. However, spores of the dacB strain were significantly more sensitive than wild-type spores to environmental UV treatments of >280 nm. Air-dried spores of the dacB mutant strain had a significantly higher water content than air-dried wild-type spores. Our results indicate that {alpha}/β-type SASP and decreased spore core water content play an essential role in spore resistance to environmentally relevant UV wavelengths whereas SASP-{gamma} does not.

* Corresponding author. Mailing address: German Aerospace Center (DLR), Institute of Aerospace Medicine, Radiation Biology Division, Research Group Photo- & Exobiology, Linder Hoehe, D-51147 Cologne, Germany. Phone: 49(2203) 601-3145. Fax: 49(2203) 61790. E-mail: ralf.moeller{at}dlr.de

{triangledown} Published ahead of print on 19 June 2009.

Applied and Environmental Microbiology, August 2009, p. 5202-5208, Vol. 75, No. 16
0099-2240/09/$08.00+0     doi:10.1128/AEM.00789-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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