Biofilm dynamics and EPS production of a thermoacidophilic bioleaching archaeon

A model for the biofilm growth by Acidianus sp. DSM 29099 on pyrite is given. In the first stage (24–48 h), reversible attachment is possible. It is accompanied by the production of adhesive compounds on the mineral surface. Biofilm formation on pyrite by Acidianus sp. DSM 29099 is a dynamic process accompanied by formation of pits and production of adhesive compounds, which after cell detachment remain as footprints. [Display omitted] •In situ visualization of biofilms and EPS of thermoacidophilic archaea on pyrite.•Direct detection of footprints of cells of Acidianus sp. DSM 29099.•EPS extraction and analysis of Acidianus in bioleaching environments.•Suggestion of a model for biofilm formation by Acidianus sp. Bioleaching of metal sulfides represents an interfacial process where biofilm formation is important in the initial steps of this process. In technical applications of bioleaching, such as reactor leaching in the temperature range of 50 up to 90 °C and also in (self-heating) heaps, thermophilic archaea play an important role and often are the leaching organisms of choice. Nevertheless, to date there is little information available on the interactions between thermoacidophilic archaea and their natural mineral substrates such as pyrite. Especially for extracellular polymeric substances (EPS) of archaea and their biofilms in bioleaching environments information is rather limited. The present work focused on investigations of biofilm dynamics and EPS production of the thermoacidophilic archaeon Acidianus sp. DSM 29099 under bioleaching conditions. The results show that biofilms are dispersed non-homogeneously on pyrite. Large parts of the pyrite surfaces remain free of cells. Cell detachment from pyrite results in microbial “footprints” which, based on lectin binding assays, consist of mannose, glucose and fucose containing compounds. A monolayer biofilm develops on pyrite after 2–4 days of incubation. In addition, the pyrite surface is covered with a layer of organic compounds. EPS analysis indicates the presence of proteins, polysaccharides and uronic acids, the composition of which varies according to substrate and lifestyle (i.e. planktonic, biofilm cells). This report provides insight into EPS and biofilm characteristics of thermophilic archaea and improves understanding of the mineral-microbial-biofilm interfacial interactions in extreme environments. Moreover, the results on interaction dynamics of archaeal microbial consortia will facilitate t