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2003
Kminek, G, Bada JL, Pogliano K, Ward JF.  2003.  Radiation-dependent limit for the viability of bacterial spores in halite fluid inclusions and on Mars. Radiation Research. 159:722-729.   10.1667/0033-7587(2003)159[0722:rlftvo]2.0.co;2   AbstractWebsite

When claims for the long-term survival of viable organisms are made, either within terrestrial minerals or on Mars, considerations should be made of the limitations imposed by the naturally occurring radiation dose to which they have been exposed. We investigated the effect of ionizing radiation on different bacterial spores by measuring the inactivation constants for B. subtilis and S. marismortui spores in solution as well as for dry spores of B. subtilis and B. thuringiensis. S. marismortui is a halophilic spore that is genetically similar to the recently discovered 2-9-3 bacterium from a halite fluid inclusion, claimed to be 250 million years old (Vreeland et al, Nature 407, 897-900, 2000). B. thuringiensis is a soil bacterium that is genetically similar to the human pathogens B. anthracis and B. cereus (Helgason et al., Appl. Environ. Microbiol 66, 2627-2630, 2000). To relate the inactivation constant to some realistic environments, we calculated the radiation regimen in a halite fluid inclusion and in the Martian subsurface over time. Our conclusion is that the ionizing dose of radiation in those environments limits the survival of viable bacterial spores over long periods. In the absence of an active repair mechanism in the dormant state, the long-term survival of spores is limited to less than 109 million years in halite fluid inclusions, to 100 to 160 million years in the Martian subsurface below 3 m, and to less than 600,000 years in the uppermost meter of Mars. (C) 2003 by Radiation Research Society.

1990
Chen, RF, Bada JL.  1990.  A Laser-Based Fluorometry System for Investigations of Seawater and Porewater Fluorescence. Marine Chemistry. 31:219-230.   10.1016/s0304-4203(05)80014-3   AbstractWebsite

A highly sensitive laser-induced fluorescence (LIF) system has been developed to study the fluorescence of dissolved organic carbon (DOC) in the marine environment. The LIF detector has a detection limit of approximately 10 attomoles (10x10(-18) moles) of pterin and eliminates internal quenching in highly fluorescent samples such as anoxic porewaters encountered when using conventional fluorometry. LIF analysis is rapid, reproducible, and uses only 100 mu-l of a sample. This small size requirement permits fluorescence analyses of samples often available only in limited amounts, such as pore-waters, hydrothermal vent waters, and rainwaters. In addition, the LIF detection system may greatly simplify extraction and separation procedures required to characterize the fluorescent components of DOC.