No abstract

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 mm 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.

Abstract-Although N 2 -fixing cyanobacteria contribute significantly to oceanic sequestration of atmospheric CO 2 , little is known about how N 2 fixation and carbon fixation (primary production) interact in natural populations of marine cyanobacteria. In a developing cyanobacterial bloom in the Baltic Sea, rates of N 2 fixation (acetylene reduction) showed both diurnal and longer-term fluctuations. The latter reflected fluctuations in the nitrogen status of the cyanobacterial population and could be correlated with variations in the ratio of acetylene reduced to 15 N 2 assimilated. The value of this ratio may provide useful information about the release of newly fixed nitrogen by a cyanobacterial population. However, although the diurnal fluctuations in N 2 fixation broadly paralleled diurnal fluctuations in carbon fixation, the longer-term fluctuations in these two processes were out of phase.

Phototrophic 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.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p244.html

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 tRNA Ile and tRNA Ala 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.Archaeological hypogea, such as Roman catacombs and the necropolis, are man-made underground sites illuminated from natural openings to the outside and/or from artificial lights that permit visits by tourists. The low-light conditions (photosynthetic photon flux density of Ͻ2 mol m Ϫ2 s Ϫ1