Original paper

Exopolysaccharides in cyanobacterial biofilms from Roman catacombs

Bellezza, Simona; Albertano, Patrizia; De Philippis, Roberto; Paradossi, Gaio


Three phototrophic biofilms dominated by Gloeothece membranacea, Scytonema julianum and Fischerella maior were collected in the Catacombs of St. Callistus and Domitilla Rome (Italy) and studied with the aim to characterize the ultrastructural features of the cyanobacterial capsules and sheaths, the chemical composition of the constituent exopolysaccharides and their physico-chemical behaviour at varying pH. Cytochemical stains in light and transmission electron microscopy allowed the detection of carboxylic and sulphated groups and positively charged glycoproteins in distinct sheath layers of filamentous cyanobacteria. Reverse phase-high performance liquid chromatography was used to determine the sugar composition of the extracted exopolysaccharides forming the mucous matrix, and showed the neutral exoses, glucose, mannose and galactose, and the charged galacturonic acid as the most abundant monosaccharides. Circular dichroism techniques were applied to assess type and chemical features of the polymers, the behaviour of which at varying pH was typical of a random coil, and confirmed the presence of uronic acids.


phototrophic biofilmscyanobacteriaepsmicroscopycytochemistrycircular dichroismbiodeteriorationconservation of stone