Exopolysaccharide composition and size in Sulfolobus acidocaldarius biofilms

Abstract

Extracellular polymeric substances (EPS) comprise mainly carbohydrates, proteins and extracellular DNA (eDNA) in biofilms formed by the thermoacidophilic Crenarchaeon Sulfolobus acidocaldarius. However, detailed information on the carbohydrates in the S. acidocaldarius biofilm EPS, i.e., the exopolysaccharides (PS), in terms of identity, composition and size were missing. In this study, a set of methods was developed and applied to study the PS in S. acidocaldarius biofilms. It was initially shown that addition of sugars, most significantly of glucose, to the basal N-Z-amine-based growth medium enhanced biofilm formation. For the generation of sufficient amounts of biomass suitable for chemical analyses, biofilm growth was established and optimized on the surface of membrane filters. EPS were isolated and the contents of carbohydrates, proteins and eDNA were determined. PS purification was achieved by enzymatic digestion of other EPS components (nucleic acids and proteins). After trifluoroacetic acid-mediated hydrolysis of the PS fraction, the monosaccharide composition was analyzed by reversed-phase liquid chromatography (RP-LC) coupled to mass spectrometry (MS). Main sugar constituents detected were mannose, glucose and ribose, as well as minor proportions of rhamnose, N-acetylglucosamine, glucosamine and galactosamine. Size exclusion chromatography (SEC) revealed the presence of one single PS fraction with a molecular mass of 4-9 × 104 Da. This study provides detailed information on the PS composition and size of S. acidocaldarius MW001 biofilms and methodological tools for future studies on PS biosynthesis and secretion.

Exopolysaccharides Producing Bacteria: A Review

“…The bioethanol producer Zymomonas mobilis is able to grow in media with an alcohol concentration of up to 16% that can be explained by the protective effect of the EPSs formed by it; the first of them consists of mannose, and the second contains galactose [ 29 ]. EPSs play an important role in bacterial adhesion, aggregation, and biofilm formation and are the main fraction of the biofilm matrix both in Gram-positive and Gram-negative bacteria [ 30 , 31 , 32 ]. EPSs of the biofilm matrix promote horizontal gene transfer, and intercellular interactions prevent the dehydration of bacteria and provide protection against external agents including antibiotics.…”

Microbial Exopolysaccharide Composites in Biomedicine and Healthcare: Trends and Advances

“…EPSs are produced in response to environmental stress conditions, such as pH and temperature, and exposure to heavy metals or inhibitors, etc. [ 2 , 3 ]. Biochemically, EPSs are carbohydrate polymers composed of glucose, galactose, and rhamnose, accompanied by non-carbohydrate moieties such as proteins, enzymes, nucleic acid, etc.…”