Pseudomonas sp. C27 is a facultative autotrophic bacterium (FAB) that can effectively conduct mixotrophic denitrifying sulfide removal (DSR) reactions using organic matters and sulfide as electron donors. Quantitative proteomics analysis of C27 using isobaric tag for relative and absolute quantitation (iTRAQ) and bioinformatics techniques identified 1916 unique proteins, based on which a novel pathway utilizing couple carbon, sulfide and nitrogen cycles for mixotrophic growth of C27. DSR experiments at different C/N ratios confirmed the presence of the new pathway. This novel pathway may be of great significance for C27-alike strains to conduct sulfide and nitrate removals in biological treatments. (C) 2014 Elsevier Ltd. All rights reserved.