Work within the DFG-SPP research unit 432 “Watt” has focused on the identification and enumeration of ANME-archaea in several meters depth (Ph.D. thesis of Kerstin Bischof), and gammaproteobacteria in the sediment surface layers that are potentially involved in oxidation of reduced sulfur compounds (Ph.D. thesis of Sabine Lenk). Both students have started to screen large fosmid libraries constructed in an attempt to use metagenomics for functional assignments to defined microbial population identified by the rRNA approach. The characterization of the sandy intertidal sediments “Hausstrand” on the island of Sylt on the group level has been published (Musat et al. 2006).

Genomic insights into Beggiatoa

In collaboration with US, Dutch, and MPI colleagues, new tools of molecular biology were used to obtain insights into the genome of single filaments of large vacuolated sulfur bacteria. Optical mapping indicated a genome size of >7 Mbp and high microdiversity. Consequently, single filaments were used for DNA isolation, multi-displacement amplification (MDA) and subsequent pyro- and Sanger-sequencing (Mussmann et al. 2007). Sequence assemblies remained incomplete with an average length of about 1 kb. Pathways for sulfur oxidation, nitrate and oxygen respiration, and CO2 fixation confirm the chemolithoautotrophic physiology of Beggiatoa. Based on the sequence information a mechanism was proposed for the unique vacuolar nitrate accumulation that is linked to proton translocation by V-type ATPases.