A group of autotrophic sulfide-oxidizing denitrifying bacteria was identified from an aged anthropogenic marine sediment treated by nitrate for the removal of recalcitrant organic residues. Based on 16S rDNA similarity, they were most closely related to Sulfurimonas denitrificans which oxidizes sulfide to sulfate using nitrate as electron acceptor. This group of bacteria was one of the eleven operational taxonomy units (OTUs) identified using a universal primer set for Eubacteria, but it was accounted for 69% of the total nitrate reduction. Using a primer set designed specifically for S. denitrificans, six new S. denitrificans-like OTUs were identified by cloning-sequencing. They had over 97% similarity with S. denitrificans and its relatives, including Thiomicrospira sp. strain CVO, Thiomicrospira sp. clone HKT806 and Campylobacterales clone DS169.