Papers in the Biological Sciences
Document Type
Article
Date of this Version
2008
Citation
Applied and Environmental Microbiology, Feb. 2008, p. 682–692, Vol. 74, No. 3
Abstract
Despite their taxonomic description, not all members of the order Sulfolobales are capable of oxidizing
reduced sulfur species, which, in addition to iron oxidation, is a desirable trait of biomining microorganisms.
However, the complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula
DSM 5348 (2.2 Mb, _2,300 open reading frames [ORFs]) provides insights into biologically catalyzed metal
sulfide oxidation. Comparative genomics was used to identify pathways and proteins involved (directly or
indirectly) with bioleaching. As expected, the M. sedula genome contains genes related to autotrophic carbon
fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of
hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus
ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin,
involved in iron oxidation, and a putative tetrathionate hydrolase, implicated in sulfur oxidation. The
fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus, was also
identified. These iron- and sulfur-oxidizing components are missing from genomes of nonleaching members of
the Sulfolobales, such as Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole-genome
transcriptional response analysis showed that 88 ORFs were up-regulated twofold or more in M. sedula upon
addition of ferrous sulfate to yeast extract-based medium; these included genes for components of terminal
oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with
sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of
the iron and sulfur metabolism of M. sedula remain to be identified and characterized.
Comments
Copyright © 2008, American Society for Microbiology. All Rights Reserved.