1. ¹Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA
2. ²Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
3. ³Department of Medical Sciences, Florida State University, Tallahassee, FL, USA

Correspondence: JK Fredrickson, Biological Sciences, Pacific Northwest National Laboratory, MS P7-50, PO Box 999, Richland, WA 99352, USA. E-mail: jim.fredrickson@pnl.gov

Received 8 September 2007; Revised 6 December 2007; Accepted 9 December 2007; Published online 14 February 2008.

Abstract

For extremely ionizing radiation-resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria and the level of cellular protein oxidation induced by desiccation. Bacteria were isolated from surface soils of the shrub-steppe of the US Department of Energy's Hanford Site in Washington State. A total of 63 isolates were used for phylogenetic analysis. The majority of isolates were closely related to members of the genus Deinococcus, with Chelatococcus, Methylobacterium and Bosea also among the genera identified. Desiccation-resistant isolates accumulated high intracellular manganese and low iron concentrations compared to sensitive bacteria. In vivo, proteins of desiccation-resistant bacteria were protected from oxidative modifications that introduce carbonyl groups in sensitive bacteria during drying. We present the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms, which limit protein oxidation during dehydration.