Archaeal biofilms: Composition of extracellular polymeric substances, exopolysaccharide synthesis and secretion in Sulfolobus acidocaldarius

Laura Kuschmierz,Benjamin Meyer,Jost Wingender,Bettina Siebers,Christopher Bräsen,Oliver J Schmitz,Sonja-Verena Albers,Martin Meyer

doi:10.5194/biofilms9-59

Abstract

&lt;p&gt;Archaea, representatives of the third domain of life, are often referred to as &amp;#8220;extremophiles&amp;#8221; since most of the cultivable species are adapted to extreme environments [1]. However, environmental cultivation-independent approaches (metagenomics) revealed a wide distribution of Archaea in moderate habitats suggesting a major role in geochemical processes. Similar to Bacteria, also Archaea are believed to exist predominantly in the biofilm mode, but knowledge about archaeal biofilm formation and structure, extracellular polymeric substance (EPS) composition and synthesis is scarce [2].&lt;/p&gt; &lt;p&gt;&lt;em&gt;Sulfolobus acidocaldarius&lt;/em&gt; is a thermoacidophilic, aerobic Crenarchaeon (78&amp;#176;C and pH 2-3) that was isolated from acid hot springs [3]. The organism is easy to cultivate under laboratory conditions and a genetic system is established. In this study, we investigate &lt;em&gt;S. acidocaldarius&lt;/em&gt; biofilms with a special focus on synthesis and transport of exopolysaccharides (PS). PS constitute a major EPS component beside proteins and eDNA, suggesting an important role in &lt;em&gt;Sulfolobus&lt;/em&gt; biofilms, and changes in PS composition were observed in response to environmental stress [4]. A gene cluster encoding several glycosyltransferases (GTs) as well as membrane proteins (MPs), likely involved in exopolysaccharide synthesis, was identified in &lt;em&gt;S. acidocaldarius&lt;/em&gt;. Several deletion mutants have been constructed lacking certain GT and MP encoding genes from the PS gene cluster. A combination of methods including the quantification of biofilm formation, isolation and quantification of EPS components, visualization of biofilm and PS structures via confocal laser scanning microscopy as well as molecular and biochemical techniques have been applied to compare biofilm characteristics of wildtype and mutant strains. First insight into the function of GTs and MPs will be presented and a model of PS synthesis and export will be proposed.&lt;/p&gt; &lt;p&gt;[1] Schocke et al. (2019).&lt;em&gt; Curr. Opin. in Biotechnol.&lt;/em&gt; 59, 71-77.&lt;/p&gt; &lt;p&gt;[2] van Wolferen et al. (2018). &lt;em&gt;Nature Rev. Microbiol.&lt;/em&gt; 16(11), 699-713.&lt;/p&gt; &lt;p&gt;[3] Brock et al. (1972). &lt;em&gt;Arch. Mikrobiol.&lt;/em&gt; 84, 54-68.&lt;/p&gt; &lt;p&gt;[4] Jachlewski et al. (2015). &lt;em&gt;Front. Bioeng. Biotechnol.&lt;/em&gt; 3, 123.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

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