Evidence for two pathways of thiosulfate oxidation in Starkeya novella (formerly Thiobacillus novellus )
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O R I G I N A L PA P E R
Ulrike Kappler · Cornelius G. Friedrich · Hans G. Trüper · Christiane Dahl
Evidence for two pathways of thiosulfate oxidation in Starkeya novella (formerly Thiobacillus novellus)
Received: 14 August 2000 / Revised: 3 November 2000 / Accepted: 7 November 2000 / Published online: 30 January 2001 © Springer-Verlag 2001
Abstract The pathway of thiosulfate oxidation in the facultatively chemolithotrophic, sulfur-oxidizing bacterium Starkeya novella (formerly Thiobacillus novellus) has not been established beyond doubt. Recently, isolation of the sorAB genes, which encode a soluble sulfite:cytochrome c oxidoreductase, has been reported, indicating that a thiosulfate-oxidizing pathway not involving a multienzyme complex may exist in this organism. Here we report the cloning and sequencing of the soxBCD genes from S. novella, which are closely related to the corresponding genes encoding the thiosulfate-oxidizing multienzyme complex from Paracoccus pantotrophus. These findings suggest two distinct pathways for thiosulfate oxidation in S. novella. The expression of sorAB and soxC in cells grown on thiosulfate- and/or glucose-containing media was studied by Western blot analysis. The results showed that the SorAB protein is synthesized in the presence of thiosulfate irrespective of the presence of glucose. In contrast, the SoxC protein is subject to repression by glucose; the repression, however, appears to be dependent on the relative amounts of glucose and thiosulfate present. The regulatory effects observed for the expression of sorAB are likely to be mediated by an extracytoplasmic function sigma factor encoded by the sigE gene identified upstream of sorAB. Keywords Thiosulfate oxidation pathway · Thiobacillus novellus · Starkeya novella · Sulfite · Sulfite oxidation · Multienzyme complex · Paracoccus pantotrophus · Sigma factor · ECF · Thiosulfate U. Kappler · H. G. Trüper · C. Dahl (✉) Institut für Mikrobiologie und Biotechnologie, Meckenheimer Allee 168, 53115 Bonn, Germany e-mail: [email protected] C. G. Friedrich Lehrstuhl für technische Mikrobiologie, Fachbereich Chemietechnik, Universität Dortmund, 44221 Dortmund, Germany Present address: U. Kappler Department of Microbiology and Parasitology, The University of Queensland, St. Lucia, Qld 4072, Australia
Abbreviations ECF Extracytoplasmic function · SOR Sulfite:cytochrome c oxidoreductase
Introduction The ability to oxidize sulfur compounds during chemolithotrophic growth has traditionally been attributed to the so-called thiobacilli (Kelly et al. 1997). Recent sequencing of the 16S and/or 5S rDNA of several members of the genus has revealed that the genus Thiobacillus is polyphyletic, and that its members are distributed among the α-, β- and γ-subdivisions of the Proteobacteria (Kelly and Wood 2000; McDonald et al. 1996). Sulfur metabolism in the former Thiobacilli comprises a complex set of reactions, many of which are not fully understood. It has been suggested that these bacteria fall into at least two major groups (reviewed by Kell
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