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Although N2-fixing cyanobacteria contribute significantly to oceanic sequestration of atmospheric CO2, little is known about how N2 fixation and carbon fixation (primary production) interact in natural populations of marine cyanobacteria. In a developing cyanobacterial bloom in the Baltic Sea, rates of N2 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 15N2 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 N2 fixation broadly paralleled diurnal fluctuations in carbon fixation, the longer-term fluctuations in these two processes were out of phase.

Ecophysiological, morphological, ultrastructural, and phylogenetic methods were used to study nine strains of Galdieria isolated from different geographical regions in order to clarify the taxonomy and evolution of the genus and to understand the phylogeny of the Cyanidiales. The studied characters were often conserved in all of the isolates. Confocal laser scanning microscopy (CLSM) observations confirmed the presence of a single plastid and allowed its 3-D reconstruction. Phylogenetic analysis showed that all Galdieria isolates but one (G. maxima) form a strongly supported monophyletic lineage within the Cyanidiales. G. maxima is closely related to Cyanidioschyzon merolae and its taxonomic status needs to be revised. The Cyanidiales is an evolutionarily distinct group within the Rhodophyta. In spite of the uniform morphology among Galdieria strains, analysis of rbcL sequences showed moderate to high levels of sequence divergence within this genus. Apart from G. maxima, which is from Kunashir, Russia, the two other Russian isolates, G. daedala and G. partita grouped together with the remaining Galdieria taxa forming three separate clades. The Galdieria clades reflected the geographic site of origin of the isolates. On the basis of these data, we suggest that Galdieria (excluding G. maxima) represents a species complex. The limited sampling makes it difficult, however, to recommend changes to the existing classification system. We suggest that a broad and systematic study of Galdieria is required to understand fully the evolutionary history and taxonomy of this genus.

12 pages, 6 figures, 1 table. et al.-- Proceedings of the International Congress on Molecular Biology and Cultural Heritage. 4-7, march, 2003, Seville, Spain., The CATS project focuses on the control, prevention and monitoring of cyanobaeteria-dominated biofilms that cause damage to rock surfaees in Roman hypogea. It develops and integrates physical and biotechnologiecal methods intended to limit the growth of microorganisms on valuable archaeological surfaces, and applies analytical methods to monitor the presence and the extent of the microbial damage. As in other hypogea, the developmet of biofilms is favoured by the limited air circulation, the even temperature throug-out the year, and the high level of humidity. Biofilms composed of sciaphilous chroococcal and filamentous cyanobacteria associated with other microorganisms develop thanks to the light gradients that occur in the proximity of entrances and artificial lamps. Terrestrial cyanobacteria and associated microorganisms are the first colonisers of exposed lithic faces and their extensive development is supported by the mineral composition of the substrata and facilitated by the porous nature of the, mostly calcareous, surfaces., This work has been supported by the EU Programme Energy, Environment and Sustainable Development, in the frame of CATS Project, contract EVK4-CT-2000-00028.

The CATS project focuses on the control, prevention and monitoring of cyanobacteria-dominated biofilms that cause damage to rock surfaces in Roman hypogea. It develops and integrates physical and biotechnological methods intended to limit the growth of microorganisms on valuable archaeological surfaces, and applies analytical methods to monitor the presence and the extent of the microbial damage. As in other hypogea, the development of biofilms is favoured by the limited air circulation, the even temperature throughout the year, and the high level of humidity. Biofilms composed of sciaphilous chroococcal and filamentous cyanobacteria associated with other microorganisms develop thanks to the light gradients that occur in the proximity of entrances and artificial lamps. Terrestrial cyanobacteria and associated microorganisms are the first colonisers of exposed lithic faces and their extensive development is supported by the mineral composition of the substrata and facilitated by the porous nature of the, mostly calcareous, surfaces.

The Southern Adriatic Sea has been so far immune from harmful algal bloom. However, in order to assess the risk of such an event, a phytoplankton monitoring was carried out with special attention to potentially toxic species. A total of 253 algal taxa were identified 18 of which were regarded as harmful, noxious, or toxin-producers. Seasonal changes of these potentially toxic populations are presented in relation to hydrographic and biotic factors. Ecological implications arising from the data are discussed on the basis of statistical analyses.