title: Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments.
abstract: Three coccoid and two filamentous cyanobacterial strains were isolated from phototrophic biofilms exposed to intense solar radiation on lithic surfaces of the Parasurameswar Temple and Khandagiri caves, located in Orissa State, India. Based on to their morphological features, the three coccoid strains were assigned to the genera Gloeocapsosis and Gloeocapsa, while the two filamentous strains were assigned to the genera Leptolyngbya and Plectonema. Eleven to 12 neutral and acidic sugars were detected in the slime secreted by the five strains. The secretions showed a high affinity for bivalent metal cations, suggesting their ability to actively contribute to weakening the mineral substrata. The secretion of protective pigments in the polysaccharide layers, namely mycosporine amino acid-like substances (MAAs) and scytonemins, under exposure to UV radiation showed how the acclimation response contributes to the persistence of cyanobacteria on exposed lithoid surfaces in tropical areas.
authors.affiliation: Department of Agricultural Biotechnology, University of Florence, Piazzale delle Cascine 24, Firenze 50144, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Rossi
authors.forename: Ernesto
authors.initials: E
authors.lastname: Micheletti
authors.forename: Laura
authors.initials: L
authors.lastname: Bruno
authors.forename: Siba P
authors.initials: SP
authors.lastname: Adhikary
authors.forename: Patrizia
authors.initials: P
authors.lastname: Albertano
authors.forename: Roberto De
authors.initials: RD
authors.lastname: Philippis
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D057219:Biofouling; D002118:Calcium / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D005296:Ferrous Compounds / Q000378:metabolism; D007194:India; D007211:Indoles / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008903:Minerals / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D052817:Phototrophic Processes; D010860:Pigments, Biological / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology; D014466:Ultraviolet Rays
chemical_list: D005296:Ferrous Compounds; D007211:Indoles; D008903:Minerals; D010636:Phenols; D010860:Pigments, Biological; D011135:Polysaccharides, Bacterial; D002734:Chlorophyll; C083368:scytonemin; D008274:Magnesium; D002118:Calcium; D000077194:Chlorophyll A