Insight Into Interactions of Thermoacidophilic Archaea With Elemental Sulfur: Biofilm Dynamics and EPS Analysis

Abstract

Biooxidation of reduced inorganic sulfur compounds (RISCs) by thermoacidophiles is of particular interest for the biomining industry and for environmental issues, e.g., formation of acid mine drainage (AMD). Up to now, interfacial interactions of acidophiles with elemental sulfur as well as the mechanisms of sulfur oxidation by acidophiles, especially thermoacidophiles, are not yet fully clear. This work focused on how a crenarchaeal isolate Acidianus sp. DSM 29099 interacts with elemental sulfur. Analysis by Confocal laser scanning microscopy (CLSM) and Atomic force microscopy (AFM) in combination with Epifluorescence microscopy (EFM) shows that biofilms on elemental sulfur are characterized by single colonies and a monolayer in first stage and later on 3-D structures with a diameter of up to 100 μm. The analysis of extracellular polymeric substances (EPS) by a non-destructive lectin approach (fluorescence lectin-barcoding analysis) using several fluorochromes shows that intial attachment was featured by footprints rich in biofilm cells that were embedded in an EPS matrix consisting of various glycoconjugates. Wet chemistry data indicate that carbohydrates, proteins, lipids and uronic acids are the main components. Attenuated reflectance (ATR)-Fourier transformation infrared spectroscopy (FTIR) and high-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) indicate glucose and mannose as the main monosaccharides in EPS polysaccharides. EPS composition as well as sugar types in EPS vary according to substrate (sulfur or tetrathionate) and lifestyle (biofilms and planktonic cells). This study provides information on the building blocks/make up as well as dynamics of biofilms of thermoacidophilic archaea in extremely acidic environments.

Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

“…These five major EPS components were selected based on the EPS components previously found in electroactive anode biofilms 20 , 46 – 48 . Furthermore, these EPS components were also found in archaeal biofilms in conventional anaerobic biofilm reactors 49 , 50 . Both EPS extraction methods (CER and heating method) provided similar results (Table S1 ).…”

Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

“…These five major EPS components were selected based on the EPS components previously found in electroactive anode biofilms 20,[46][47][48] . Furthermore, these EPS components were also found in archaeal biofilms in conventional anaerobic biofilm reactors 49,50 . Both EPS extraction methods (CER and heating method) provided similar results (Table S1).…”

A biochemical view on the biological sulfur cycle

“…Biofilms formed on the surface of elemental sulfur by cells of the thermoacidophilic archaeal species Acidianus also comprise an extracellular matrix that contains carbohydrates, proteins and lipids. The lipids are suggested to mediate initial attachment of the cells to sulfur while sugars like glucose and mannose are thought to be important for further colonization of sulfur and a mature biofilm architecture (Zhang et al, 2019). For the purple sulfur bacterium A. vinosum, intimate physical cell-sulfur contact was also established as a prerequisite for sulfur uptake (Franz et al, 2007).…”