Abstract

Abstract In this chapter we provide an overview of the biofilm lifestyle of (hyper) thermophilic and acidophilic archaea. In contrast to the bacterial domain, biofilm formation of archaea is far less studied and understood. Recent evidence has shown that upon biofilm formation, archaeal cells are able to secrete extracellular polymeric substances (EPS), whose composition changes according to available energy sources, environmental fluctuations and biofilm maturity. Also, several type IV pili-like surface cell appendages (e.g. the archaellum and the aap pili) have been shown to be involved in the initial attachment of archaea to surfaces. Little is known about cell-to-cell interactions and potential cell-to-cell communication mechanisms in archaea. Therefore, molecules and signaling pathways involved in these processes might be substantially different from what it is already described in bacteria. Recently, the first archaeal transcriptional regulators involved in biofilm formation have been discovered in Sulfolobus species. Future avenues in archaeal biofilm research include: (i) the EPS biosynthesis pathways and biofilm-specific bio-molecules, (ii) cell-to-cell communication mechanisms and microbial interactions within multispecies archaeal biofilms, as well as (iii) potential interaction with bacterial and eukaryotic microorganisms. Finally, biotechnological applications of thermophilic and acidophilic archaeal biofilms are discussed.