The Mth60 fimbriae of Methanothermobacter thermoautotrophicus are functional adhesins

The ability to adhere onto surfaces is of very high importance for microorganisms, enabling them to stay in a favourable habitat for life. In the case of Bacteria cell surface organelles called fimbriae/pili have been shown to be used for adhesion; corresponding cell surface appendages of Archaea have not yet been defined. The first detailed characterization of archaeal fimbriae, namely those of Methanothermobacter thermoautotrophicus, allowed us to identify mth60 as the main structural fimbrin gene. Recombinant expression of mth60 in Escherichia coli was used to generate sufficient amounts of Mth60 to induce antibodies in rabbits. The antiserum reacted specifically with the 16 kDa fimbrial glycoprotein and could specifically detach adhering M. thermoautotrophicus cells from various surfaces. In addition we proved that cells adhering to solid surfaces - organic and inorganic ones - express many more fimbriae than cells growing in liquid cultures. The Mth60 fimbriae therefore are used by M. thermoautotrophicus as adhesins.