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Ron Oremland

Publications and source records attributed to Ron Oremland.

5 recordsLinked to original sources
USGS2015

Stable carbon isotope fractionation during bacterial acetylene fermentation: Potential for life detection in hydrocarbon-rich volatiles of icy planet(oid)s

We report the first study of stable carbon isotope fractionation during microbial fermentation of acetylene (C 2 H 2 ) in sediments, sediment enrichments, and bacterial cultures. Kinetic isotope effects (KIEs) averaged 3.7 ± 0.5‰ for slurries prepared with sediment collected at an intertidal mudflat in San Francisco Bay and 2.7 ± 0.2‰ for a pure culture of Pelobacter sp. isolated from these sediments. A similar KIE of 1.8 ± 0.7‰ was obtained for methanogenic enrichments derived from sediment collected at freshwater Searsville Lake, California. However, C 2 H 2 uptake by a highly enriched mixed culture (strain SV7) obtained from Searsville Lake sediments resulted in a larger KIE of 9.0 ± 0.7‰. These are modest KIEs when compared with fractionation observed during oxidation of C 1 compounds such as methane and methyl halides but are comparable to results obtained with other C 2 compounds. These observations may be useful in distinguishing biologically active processes operating at distant locales in the Solar System where C 2 H 2 is present. These locales include the surface of Saturn's largest moon Titan and the vaporous water- and hydrocarbon-rich jets emanating from Enceladus.

Astrobiology↗
USGS2014

Dissimilatory reduction of selenate and arsenate in nature

This chapter discusses the biogeochemical reduction of selenate (Se(VI)) and arsenate (As(V)) when they enter anoxic environments and are used as electron acceptors for the oxidation of organic matter. These reductions are of a dissimilative nature and support the anaerobic growth of selected bacteria which conserve energy from this process. The chapter summarizes what is known about the bacteria's taxonomy, physiology, and biochemistry. Reduction to the solid, relatively unreactive Se(0) represents a mechanism for the removal of toxic Se(VI) and Se(IV) from natural waters. The environmental ramifications of these issues are also discussed in the chapter. The number of bacterial species known to respire selenate and arsenate continues to increase. The biological reduction of selenate and arsenate occurs for a number of reasons. In general, these are assimilation, regulation of reducing equivalents, detoxification, and dissimilation. Each is discussed in detail in the chapter. The realization that arsenate and selenate are indeed suitable electron acceptors and are readily available in both natural and contaminated environments suggests that even more unrelated species will be discovered. The initial biochemical studies also suggest that there may be different pathways for selenate and arsenate reduction, with specific terminal reductases and cytochromes.

Book chapter↗
USGS2011

Arsenic

No abstract available.

Book chapter↗
USGS2007

Alkalilimnicola ehrlichii sp. nov., a novel, arsenite-oxidizing haloalkaliphilic gammaproteobacterium capable of chemoautotrophic or heterotrophic growth with nitrate or oxygen as the electron acceptor

A facultative chemoautotrophic bacterium, strain MLHE-1 T , was isolated from Mono Lake, an alkaline hypersaline soda lake in California, USA. Cells of strain MLHE-1 T were Gram-negative, short motile rods that grew with inorganic electron donors (arsenite, hydrogen, sulfide or thiosulfate) coupled with the reduction of nitrate to nitrite. No aerobic growth was attained with arsenite or sulfide, but hydrogen sustained both aerobic and anaerobic growth. No growth occurred when nitrite or nitrous oxide was substituted for nitrate. Heterotrophic growth was observed under aerobic and anaerobic (nitrate) conditions. Cells of strain MLHE-1 T could oxidize but not grow on CO, while CH 4 neither supported growth nor was it oxidized. When grown chemoautotrophically, strain MLHE-1 T assimilated inorganic carbon via the Calvin–Benson–Bassham reductive pentose phosphate pathway, with the activity of ribulose 1,5-bisphosphate carboxylase (RuBisCO) functioning optimally at 0.1 M NaCl and at pH 7.3. Strain MLHE-1 T grew over broad ranges of pH (7.3–10.0; optimum, 9.3), salinity (15–190 g l −1 ; optimum 30 g l −1 ) and temperature (13–40 °C; optimum, 30 °C). Phylogenetic analysis of 16S rRNA gene sequences placed strain MLHE-1 T in the class Gammaproteobacteria (family Ectothiorhodospiraceae ) and most closely related to Alkalispirillum mobile (98.5 %) and Alkalilimnicola halodurans (98.6 %), although none of these three haloalkaliphilic micro-organisms were capable of photoautotrophic growth and only strain MLHE-1 T was able to oxidize As(III). On the basis of physiological characteristics and DNA–DNA hybridization data, it is suggested that strain MLHE-1 T represents a novel species within the genus Alkalilimnicola for which the name Alkalilimnicola ehrlichii is proposed. The type strain is MLHE-1 T (=DSM 17681 T =ATCC BAA-1101 T ). Aspects of the annotated full genome of Alkalilimnicola ehrlichii are discussed in the light of its physiology.

California↗