HR: 10:35h
AN: B12A-02 INVITED    [Abstracts]
TI: Probing for the Activities of Arsenic and Selenium Metabolizing Microbes
AU: * Stolz, J F
EM: stolz@duq.edu
AF: Duquesne University, Department of Biological Sciences, Pittsburgh, PA 15282, United States
AB: Microbial activities can directly impact the mobility and toxicity of arsenic and selenium in the environment. Arsenic is cycled through oxidation/reduction and methylation/demethylation reactions as part of resistance and respiratory processes. The requirement for selenium is primarily for incorporation into selenocysteine and its function in selenoenzymes. Selenium oxyanions can also serve as an electron acceptor in anaerobic respiration. Both culture and culture-independent methods have been developed to detect the presence and activity of organisms capable of arsenic and selenium transformations. Enrichment media have been successful at cultivating arsenate respiring bacteria from a variety of environments, however, both electron donor and the concentration of arsenic can exert strong selective pressure. Thus, the organisms in the enrichment culture may not be the dominant organisms in the environment. Culture-independent methods, including immunological approaches (e.g., polyclonal antibodies to ArrA) and PCR-based technologies, have also had mixed success. PCR-primers designed to amplify portions of genes involved in resistance (e.g., arsC, acr3), respiration (e.g., arrA), and oxidation (e.g., aoxB) have been useful in several environments. Applications include T-RFLP, rt-PCR, and DGGE analyses. Nevertheless, these primers do not work with certain organisms suggesting the existence of additional enzymes and pathways. Although the biosynthetic pathway (and the proteins involved) for selenocysteine has been described in detail, much less is known about selenium methylation, assimilation and respiration. Only one respiratory selenate reductase has been characterized and its close sequence identity with chlorate and perchlorate reductases has complicated efforts to design a functional probe. Thus many aspects of the biogeochemical cycle of selenium remains to be explored.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0448 Geomicrobiology
DE: 0463 Microbe/mineral interactions
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting