Novel uncultured Deltaproteobacteria populations (MSME Cluster) are dominant under chemolithotrophic manganese(IV)-reducing conditions in marine sediment slurry incubations

It is a three decade-old observation that when poorly-crystalline Mn(IV) is added to marine sediments, there is a rapid formation of sulfate which is linked to biological activity. However, knowledge of the diversity of microorganisms involved in this reaction is limited. 454-pyrosequencing analysis of bacterial 16S rRNA genes revealed a rapid enrichment (55-60% of total bacteria in 4 days from less than 1% on day 0) of novel uncultured Deltaproteobacteria (tentatively named Marine Sediment Manganese-reducing Enrichment, MSME Cluster) in MnO2 (Birnessite)-treated slurry incubations with sediment from the Helgoland mud area, North Sea. This finding further expands the diversity of microbes involved in Mn(IV)-dependent sulfate formation in marine sediments. Efforts are underway to further unravel the distribution and roles of MSME bacterial groups in S-Mn cycling in marine sediments