Patrizia Albertano

Cultured phototrophic biofilms for phosphorus removal in wastewater treatment

Culture experiments with phototrophic biofilms taken from the sedimentation tank of the wastewater treatment plant at the Fiumicino Airport in Rome, Italy were carried out in a prototype continuous flow incubator. Biofilms grown at varying photosynthetic photon flux density (PPFD), temperature and flow velocity were sampled at three developmental stages to quantify biofilm dry weight, chlorophyll a concentration and total cellular phosphorus content. While no coherent significant effects by flow and temperature were evidenced, maximum biofilm dry weight and phosphorous concentration significantly increased across all featured PPFDs. Maximum chlorophyll a concentration was saturated above 60 micromol m(-2)s(-1). A highly significant association between organic biomass and phosphorous content was observed for most light conditions, including a larger proportional increase of phosphorus concentration with respect to chlorophyll a at high PPFD. Up to 112 mg P m(-2)d(-1) maximal phosphorous removal rates were achieved. Elemental analysis by energy filtering transmission electron microscopy showed subcellular localization of phosphorus, confirming the accumulation in phototrophic microorganisms in biofilms grown in high light conditions.

Structural Interactions among Epilithic Cyanobacteria and Heterotrophic Microorganisms in Roman Hypogea.

A bstractPhototrophic microbial communities present in the Roman Catacombs were characterized and different species of terrestrial epilithic cyanobacteria were found to occur as dominant organisms. Eucapsis, Leptolyngbya, Scytonema, and Fischerella were the most frequently encountered cyanobacterial taxa, while a few species of green algae and the diatom Diadesmis gallica occurred in minor amounts. Streptomyces strains, a few genera of eubacteria, and to a lesser extent fungi were always present in the same microhabitats and contributed to the deterioration of stone surfaces. The combined use of light and electron microscopy evidenced the structural relationships among rod-shaped or filamentous bacteria and cyanobacterial cells, as well as the presence of polysaccharide capsules and sheaths, and of mineral precipitates on S. julianum filaments. The significance of the intimate association among the microorganisms was discussed in relation to the damage caused by the growth of biological patinas on stone surfaces.

The taxonomic position of Cyanidium, Cyanidioschyzon and Galdieria: an update

The ecophysiological, cytomorphological, biochemical and molecular data presently available for the acidophilic red algal species Cyanidium caldarium, Cyanidioschyzon merolae and Galdieria sulphuraria are summarised. The taxonomic position of the three genera is discussed and emendements to the generic diagnosis are presented.

Cytomorphological and Genetic Characterization of Troglobitic Leptolyngbya Strains Isolated from Roman Hypogea

ABSTRACT Six Leptolyngbya strains, isolated from the archaeological surfaces of hypogean sites, were phenotypically and genetically characterized by light and electron microscopy and 16S rRNA gene and 16S-23S internally transcribed spacer (ITS) sequencing. Three phycoerythrin-rich (red) and three phycocyanin-rich (green) isolates were assigned to different operational taxonomic units (OTUs). Among the green isolates, one strain showed an OTU intraspecific variation due to differences in the ITS sequences and genomic polymorphism. Within the ITS sequence, variable regions, conserved domains and tRNAIle and tRNAAla genes showed high sequence identity among the phylotypes. Together, these data indicated a relatedness of the six strains to other Leptolyngbya from subaerophytic and geothermal environments and allowed the definition of novel Leptolyngbya OTUs.

Microbial diversity in paleolithic caves: a study case on the phototrophic biofilms of the Cave of Bats (Zuheros, Spain)

The biological colonization of rocks in the Cave of Bats (Cueva de Los Murciélagos, Zuheros, Spain) was studied in order to reveal the diversity of microorganisms involved in the biofilm formation. The culturable, metabolically active fraction of biodeteriogens present on surfaces was investigated focusing on morphological, ultrastructural, and genetic features, and their presence related to the peculiar environmental conditions of the underground site. PCR-ITS analysis and 16S rDNA sequences were used to clusterize and characterize the isolated strains. The presence of bacterial taxa associated to the photosynthetic microflora and fungi within the biofilm contributed to clarify the relationships inside the microbial community and to explain the alteration observed at the different sites. These results will contribute to the application of more successful strategies for the preventive conservation of subterranean archaeological sites.

Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments.

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.

The subaerophytic cyanobacterium Oculatella subterranea (Oscillatoriales, Cyanophyceae) gen. et sp. nov.: a cytomorphological and molecular description

A new genus and species of subaerophytic cyanobacteria with very thin purple-red trichomes are described. The seven strains included in this genus were isolated from phototrophic biofilms growing on calcareous substrata in ancient hypogea. Trichomes were 1–3 µm thick, with small constrictions at the cross-walls and colourless sheaths. The thylakoid arrangement was parietal. Autapomorphic characters include the purple-red colouration of cells and a photosensitive orange spot at the tip of the trichome containing a rhodopsin-like pigment. Molecular and phylogenetic analyses based on 16 S rRNA gene sequences, resulted in a new 16 S rRNA cluster that indicated a separate position at the generic level. All strains were closely related (99% or higher similarity) and distantly related to other established cyanobacterial taxa (92%). The 16 S–23 S rRNA internal transcribed spacer (ITS) sequence of five of the red strains was almost identical. The ITS secondary folding structure was also unique to these strains and different to the Leptolyngbya type species. These strains have only been isolated from subterranean environments so far, and considering also this unique biotope and their particular ecology, we propose the new genus and species Oculatella subterranea. The genus name Oculatella means ‘provided with a small eye’. The new genus is described using combined molecular and cytomorphological criteria, in accordance with the nomenclatorial recommendations of both the Bacteriological Code and the Botanical Code of Nomenclature. The genus Oculatella is of common distribution in hypogea and has been isolated from all hypogean environments so far studied in Rome and Malta. The type strain is VRUC135.

Characterization of biofilm-forming cyanobacteria for biomass and lipid production

This work reports on one of the first attempts to use biofilm‐forming cyanobacteria for biomass and lipid production.

Capsular polysaccharides of cultured phototrophic biofilms.

Phototrophic biofilm samples from an Italian wastewater treatment plant were studied in microcosm experiments under varying irradiances, temperatures and flow regimes to assess the effects of environmental variables and phototrophic biomass on capsular exopolysaccharides (CPS). The results, obtained from circular dichroism spectroscopy and High Performance Liquid Chromatography, suggest that CPS have a stable spatial conformation and a complex monosaccharide composition. The total amount present was positively correlated with the biomass of cyanobacteria and diatoms, and negatively with the biovolume of green algae. The proportion of uronic acids showed the same correlation with these taxon groups, indicating a potential role of cyanobacteria and diatoms in the removal of residual nutrients and noxious cations in wastewater treatment. While overall biofilm growth was limited by low irradiance, high temperature (30°C) and low flow velocity (25 l h−1) yielded the highest phototrophic biomass, the largest amount of CPS produced, and the highest proportion of carboxylic acids present.

Effect of photosynthesis on pH variation in cyanobacterial biofilms from Roman catacombs

Cyanobacterial biofilms present on stone surfaces inRoman hypogea were studied with the aim of assessingtheir deteriogenic activity on the colonisedsubstrata. In order to achieve this, non-destructivemethods were developed and applied to measure pHvariation induced via photosynthesis and respirationin representative cyanobacteria from Roman catacombs.Amperometric and potentiometric microsensors were alsoused on Scytonema biofilms in culture in orderto measure photosynthesis and assess pH decreases andincreases during dark–light periods. Measurementsof pH showed that, starting with values slightly belowneutral, the pH in Scytonema biofilms increasedby 0.24–0.77 units in the transition from dark to1000 μmol photon m-2 s-1 irradiance.Comparison of photosynthesis and pH curves recordedsimultaneously on the same artificial biofilm showeda maximum increase in pH value at irradiances higherthan those saturating photosynthesis. Alkalinisationof the substrate during illumination occurred to asufficient extent to induce precipitation of mineralcompounds, especially on calcareous substrates such asthose present in Roman hypogea.