Characterization of Glycoconjugates of Extracellular Polymeric Substances in Tufa-Associated Biofilms by Using Fluorescence Lectin-Binding Analysis

Abstract

Freshwater tufa deposits are the result of calcification associated with biofilms dominated by cyanobacteria. Recent investigations highlighted the fact that the formation of microbial calcium carbonates is mainly dependent on the saturation index, which is determined by pH, the ion activity of Ca 2؉ and CO 3 2؊ , and the occurrence of extracellular polymeric substances (EPS) produced by microorganisms. EPS, which contain carboxyl and/or hydroxyl groups, can strongly bind cations. This may result in inhibition of CaCO 3 precipitation. In contrast, the formation of templates for crystal nucleation was reported by many previous investigations. The purposes of this study were (i) to characterize the in situ distribution of EPS glycoconjugates in tufa-associated biofilms of two German hard-water creeks by employing fluorescence lectin-binding analysis (FLBA), (ii) to verify the specific lectin-binding pattern by competitive-inhibition assays, and (iii) to assess whether carbonates are associated with structural EPS domains. Three major in situ EPS domains (cyanobacterial, network-like, and cloud-like structures) were detected by FLBA in combination with laser scanning microscopy (LSM). Based on lectin specificity, the EPS glycoconjugates produced by cyanobacteria contained mainly fucose, amino sugars (N-acetyl-glucosamine and N-acetyl-galactosamine), and sialic acid. Tufa deposits were irregularly covered by network-like EPS structures, which may originate from cyanobacterial EPS secretions. Cloud-like EPS glycoconjugates were dominated by sialic acid, amino sugars, and galactose. In some cases calcium carbonate crystals were associated with cyanobacterial EPS glycoconjugates. The detection of amino sugars and calcium carbonate in close association with decaying sheath material indicated that microbially mediated processes might be important for calcium carbonate precipitation in freshwater tufa systems.

Isolation, characterization and localization of extracellular polymeric substances from the cyanobacteriumArthrospira platensisstrain MMG-9

“…reported to be less suitable for detection of the sheath or TEPS (Zippel & Neu, 2011). Lotus-FITC stains fucose in EPS and it seemed to stain particularly the REPS.…”

“…The use of lectins is an elegant method to visualize different types of microbial EPS (Zippel & Neu, 2011). Furthermore, the use of optical sectioning with confocal laser scanning microscopy enables 3D imaging of undamaged cyanobacterial trichomes along with their surrounding EPS (Barranguet et al, 2004).…”

Specific carbonate–microbe interactions in the modern microbialites of Lake Alchichica (Mexico)

“…Fluorescent calcein incorporates into growing calcium carbonate structures and has been traditionally used for identification and measurement of growth of many animals, including fishes, mammals, gastropods, echinoderms (see Moran, 2000), as well as the detection of growing carbonates around bacteria (Zippel and Neu, 2011). Microbialite fragments (14-15 m depth) fixed in RNAlater or freshly collected from the laboratory aquarium were stained with calcein (0.1 mg ml À 1 ) for 36 h at 4 1C in RNAlater or at room temperature in aquarium water.…”

Electric Charge Characteristics of Biofilms Formed on Various Surfaces

“…Hence, amines have pKa's around 11, and thus, at pHs lower than around 11, amines will be protonated (i.e., NH 3 + ). The presence of amino groups in the biofilm polymers has been reported also by previous studies [8,[13][14][15]. The pH of the buffer solution used in the EPM measurement increased after the biofilm samples were added (Table 1), e.g., buffer solutions with pH 4.0 and 5.0 shifted to 5.4 and 5.9, respectively.…”