Archaeal Diversity in a Municipal Wastewater Sludge

The diversity of Archaea in a municipal wastewater sludge sample was investigated by amplification of ribosomal RNA genes from sludge DNA using archaeal-specific primers. Surprisingly, a large fraction (32%) of these sequences were from Halobacteriales, not previously seen in surveys of wastewater sludge. Other abundant sequences were from members of uncultivated ‘environmental’ archaeal groups that are commonly detected in sludge and sediment environments. Only a few distant relatives of Methanosarcina (which are commonly thought of as the predominant methanogenic species in sludge environments) were detected.