Diversity and metabolic characteristics of cultivable thermophilic arsenic transformers from geothermal springs in Taiwan and the Philippines
Date Issued
2011
Date
2011
Author(s)
Lu, Guang-Sin
Abstract
Geothermal springs typically contain high arsenic concentrations that are considered to be toxic to microorganisms. Understanding how microbially-catalytic reactions are involved in the changes of the redox state of arsenic would provide important constraints on the interaction between arsenic and microorganisms in natural occurrences. The first aim of this study was to isolate and characterize the physiological properties of thermophilic arsenic transformers in order to enhance our understanding about the global diversity and microbial role in the arsenic cycling in geothermal environments. To date, there is no literature that summarizes arsenic transforming mechanisms in connection with phylogenetic relationships. Therefore, the second aim of this study was to synthesize and summarize the relationships between the phylogeny and arsenic metabolism for cultivable strains previously published in liteatures.
Geothermal fluid samples collected from Taiwan and Philippines were inoculated into arsenite-containing media and incubated at 40 to 90oC. Five strains were isolated through plating or series dilution from the Ta-Tun volcanic area and Kuan-Tzu-Ling mud spring; thirty-five strains from the shallow submarine hydrothermal vent in the Kuei-Shan Island. Twenty strains were isolated from previous studies or provided by Dr. Chun-Yao Chen. Of these strains, nine thermophilic strains were further subject to the characterization of their arsenic transforming capabilities. Among these strains, Alicyclobacillus- and Anoxybacillus- related strains were identified to oxidize arsenite. In contrast, Acidianus- and Geobacillus-related strains were capable of reducing arsenate. Meiothermus- and Thermus-related strains were able to dually transform arsenic species. Three mesophilic strains obtained from the Kuei-Shan Island were chemolithoautotrophic arsenite oxidizers. The capability of transforming arsenic redox states by strains of Alicyclobacillus-, Anoxybacillus-, Acidianus-, Geobacillus-, Meiothermus-, and Alcanivorax- genus is first reported. These results not only expand the current view about the diversity of arsenic transformers in geothermal environments, but also facilitate to establish the linkages between microbial activities and in situ arsenic transforming processes.
The relationships between the phylogeny and arsenic metabolism was summarized as followed: heterotrophic arsenite oxidizers predominantly appear in Deinococcus-Thermus, Alphaproteobacteria, Betaproteobacteria and Psudomonas of Gammaproteobacteria; chemoautotrophic arsenite oxidizers were composed of members related with Alphaproteobacteria and Betaproteobacteria, and some strains in Gammaproteobacteria and Aquificae; dissimilatory arsenate-reducing prokaryotes were primarily affiliated with Pyrobaculum, Chrysiogenetes, Firmicutes, Deltaproteobacteria, Epsilonproteobacteria, and some Aquificae and Gammaproteobacteria members; heterotrophic arsenate reducers erratically scatter in almost all taxa, including Crenarchaeota, Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Firmicutes, Alphaproteobacteria, and Gammaproteobacteria. The results show that arsenic transforming mechanisms could be correlated with certain phylogenetic clades.
Subjects
arsenic metabolism
thermophile
geothermal ecosystem
Taiwan
the Philippines
Type
thesis
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