Towards a molecular picture of the archaeal cell surface.

Archaea produce various protein filaments with specialised functions. While some archaea produce only one type of filament, the archaeal model species Sulfolobus acidocaldarius generates four. These include rotary swimming propellers analogous to bacterial flagella (archaella), pili for twitching motility (Aap), adhesive fibres (threads), and filaments facilitating homologous recombination upon UV stress (UV pili).

CryoEM reveals the structure of an archaeal pilus involved in twitching motility.

Amongst the major types of archaeal filaments, several have been shown to closely resemble bacterial homologues of the Type IV pili (T4P). Within Sulfolobales, member species encode for three types of T4P, namely the archaellum, the UV-inducible pilus system (Ups) and the archaeal adhesive pilus (Aap). Whereas the archaellum functions primarily in swimming motility, and the Ups in UV-induced cell aggregation and DNA-exchange, the Aap plays an important role in adhesion and twitching motility.

Structure of the two-component S-layer of the archaeon .

Surface layers (S-layers) are resilient two-dimensional protein lattices that encapsulate many bacteria and most archaea. In archaea, S-layers usually form the only structural component of the cell wall and thus act as the final frontier between the cell and its environment. Therefore, S-layers are crucial for supporting microbial life.

Structural characterization of a novel cyclic 2,3-diphosphoglycerate synthetase involved in extremolyte production in the archaeon .

The enzyme cyclic di-phosphoglycerate synthetase that is involved in the production of the osmolyte cyclic 2,3-diphosphoglycerate has been studied both biochemically and structurally. Cyclic 2,3-diphosphoglycerate is found exclusively in the hyperthermophilic archaeal methanogens, such as , , and . Its presence increases the thermostability of archaeal proteins and protects the DNA against oxidative damage caused by hydroxyl radicals.