AME 45:301-312 (2006)  -  doi:10.3354/ame045301

Seasonal succession of phototrophic biofilms in an Italian wastewater treatment plant: biovolume, spatial structure and exopolysaccharides

Roberta Congestri1,*, Francesca Di Pippo1, Roberto De Philippis3, Isabella Buttino4, Gaio Paradossi2, Patrizia Albertano1

1Department of Biology, and 2Department of Chemical Sciences and Technologies, University of Rome ‘Tor Vergata’, Via della Ricerca Scientifica 1, 00133 Rome, Italy
3Department of Agricultural Biotechnology, University of Florence, Piazzale delle Cascine 24, 50144 Florence, Italy
4Laboratory of Ecophysiology, Stazione Zoologica ‘A. Dohrn’, Villa Comunale, 80121 Naples, Italy

ABSTRACT: A multiphasic approach was applied to investigate the structural features of phototrophic biofilms that grow in a wastewater treatment plant (WWTP) at Fiumicino Airport (Rome, Italy). Seasonal variations in species composition, biomass and exopolysaccharides produced were analyzed by light (LM) and electron microscopy (SEM), high performance liquid chromatography (HPLC) and circular dichroism (CD). Phototroph contribution to the 3-dimensional structure of the biofilm and its development was assessed by confocal laser scanning microscopy. Analysis of biofilms grown on polypropylene slides showed a stable species composition; seasonal changes in biomass were mostly due to changes of major cyanobacterial and algal taxonomic groups. Extensive growth was evident on the range of artificial substrata that were implanted in the treatment plant. CD spectra and HPLC analyses of 2 operationally defined exopolysaccharide fractions extracted from samples scraped off the tank walls revealed that negatively charged heteropolysaccharides comprised most of the matrix and capsular components of the biofilms. Cytochemical staining distinguished between acidic and sulphated residues in the samples observed by LM. The data provide a new insight into the structural integrity and development of phototrophic biofilms in this hyper-eutrophic environment, indicating a potential use of autochthonous consortia in an environmentally sound tertiary water treatment alternative to conventional chemico-physical technologies.

KEY WORDS: Phototrophic biofilms · Exopolysaccharides · Cyanobacteria · Algae · Biovolume · Confocal laser scanning microscope · Wastewater treatment plant

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