ABSTRACTMolecular analysis of bacteria enriched under in situ-like conditions and mechanically isolated by micromanipulation showed that a hitherto-uncultivated microaerophilic bacterium thriving in oxygen-sulfide counter-gradients (R. Thar and M. Kühl, Appl. Environ. Microbiol. 68:6310-6320, 2000) is affiliated with the ε-subdivision of theProteobacteria. The affiliation was confirmed by the use of whole-cell hybridization with newly designed specific oligonucleotide probes. The bacterium belongs to a new genus and received the provisional name “CandidatusThioturbo danicus.”