Multi-Element-Methylation in Methanoarchaea (“Methanogens”)
Methylated volatile and toxic derivatives of heavy elements like arsenic, antimony, bismuth, selenium and tellurium are especially formed in anaerobic microbial habitats like sewage sludge, landfills, alluvial soils and even the gut of mammals including men. Of all groups of organisms tested for their capability to methylate these elements, methanoarchaea are by far the most versatile ones. We aim to elucidate the pathways leading to metal(loid) methylation in methanoarchaea (as well as to identify the involved parameters in the cell, using Methanosarcina mazei as our model organism). Furthermore, as methanoarchaea also inhabit the human gut (e.g. Methanobrevibacter smithii), the medical consequences of their physiology on the healthiness of men are investigated.
Structural Adaptation to High Temperature in Archaea
Most eukaryotic organisms, including humans, but also plenty of the prokaryotic Bacteria, are mesophilic with optimal growth temperatures around 30 °C. However, especially members of Archaea are adapted to extreme temperatures as 100 °C and higher. Therefore, “hyperthermophilic” Archaea employ a series of modifications of the structure of their macromolecules such as proteins, polynucleotides and membranes. We are interested in these modifications and their thermoadaptive function.
Role of Intracellular Milieu in Archaeal Thermoadaptation
Not only macromolecules are engaged in thermoadaptation of Archaea but also low molecular compounds, so-called thermocompatibles, which accumulate in the cell at higher temperature and stabilize proteins in vitro. We are interested in the temperature-regulation of their intracellular concentration and their practical application.
Clustered Regulatory Interspaced Short Palindromic Repeats (CRISPR) in Hyperthermophilic Archaea
Intergenic regions are sometimes characterized by highly conserved repeat sequences. Some of these conserved repeat sequences in prokaryotes (Archaea and Bacteria) are short (24 – 47 nt) direct repeats with weak palindromic pattern, separated by similarly sized non-repetitive spacer sequences. These repeats are termed Clustered Regulatory Interspaced Short Palindromic Repeats (CRISPR).
Many examples pointed out that the CRISPR/Cas system is a phage-defense mechanism, analog to the eukaryotic RNAi system. However, the surprisingly high number of CRISPR loci found in hyperthermophilic Archaea as well as the lack of sequence homology to known phages of hyperthermophilic Archaeum Thermoproteus tenax motivates us to analyze whether the CRISPR system may also play a role in response to abiotic stress such as high temperature, increased salt concentration and UV irradiation.