title: Kinetic enrichment of 34S during proteobacterial thiosulfate oxidation and the conserved role of SoxB in S-S bond breaking.
abstract: During chemolithoautotrophic thiosulfate oxidation, the phylogenetically diverged proteobacteria Paracoccus pantotrophus, Tetrathiobacter kashmirensis, and Thiomicrospira crunogena rendered steady enrichment of (34)S in the end product sulfate, with overall fractionation ranging between -4.6‰ and +5.8‰. The fractionation kinetics of T. crunogena was essentially similar to that of P. pantotrophus, albeit the former had a slightly higher magnitude and rate of (34)S enrichment. In the case of T. kashmirensis, the only significant departure of its fractionation curve from that of P. pantotrophus was observed during the first 36 h of thiosulfate-dependent growth, in the course of which tetrathionate intermediate formation is completed and sulfate production starts. The almost-identical (34)S enrichment rates observed during the peak sulfate-producing stage of all three processes indicated the potential involvement of identical S-S bond-breaking enzymes. Concurrent proteomic analyses detected the hydrolase SoxB (which is known to cleave terminal sulfone groups from SoxYZ-bound cysteine S-thiosulfonates, as well as cysteine S-sulfonates, in P. pantotrophus) in the actively sulfate-producing cells of all three species. The inducible expression of soxB during tetrathionate oxidation, as well as the second leg of thiosulfate oxidation, by T. kashmirensis is significant because the current Sox pathway does not accommodate tetrathionate as one of its substrates. Notably, however, no other Sox protein except SoxB could be detected upon matrix-assisted laser desorption ionization mass spectrometry analysis of all such T. kashmirensis proteins as appeared to be thiosulfate inducible in 2-dimensional gel electrophoresis. Instead, several other redox proteins were found to be at least 2-fold overexpressed during thiosulfate- or tetrathionate-dependent growth, thereby indicating that there is more to tetrathionate oxidation than SoxB alone.
authors.affiliation: Department of Microbiology, Bose Institute, Calcutta, India.
authors.forename: Masrure
authors.initials: M
authors.lastname: Alam
authors.forename: Prosenjit
authors.initials: P
authors.lastname: Pyne
authors.forename: Aninda
authors.initials: A
authors.lastname: Mazumdar
authors.forename: Aditya
authors.initials: A
authors.lastname: Peketi
authors.forename: Wriddhiman
authors.initials: W
authors.lastname: Ghosh
mesh_terms: D042401:Alcaligenaceae / Q000378:metabolism*; D052818:Autotrophic Processes; D001426:Bacterial Proteins / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism*; D010084:Oxidation-Reduction; D042084:Paracoccus pantotrophus / Q000201:enzymology / Q000378:metabolism*; D044147:Piscirickettsiaceae / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013460:Sulfur Isotopes / Q000378:metabolism; D013885:Thiosulfates / Q000378:metabolism*; D057825:Two-Dimensional Difference Gel Electrophoresis
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D020543:Proteome; D013460:Sulfur Isotopes; D013885:Thiosulfates; D006867:Hydrolases