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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2007.05.006 Byline: Mirko Magagnini (a), Cinzia Corinaldesi (a), Luis S. Monticelli (b), Emilio De Domenico (c), Roberto Danovaro (a) Keywords: Viruses; Prokaryotes; Mesopelagic and bathypelagic waters Abstract: Despite the fact that marine viruses have been increasingly investigated in the last decade, knowledge on virus abundance, biomass and distribution in mesopelagic and bathypelagic waters is limited. We report here the results of a large-spatial-scale study (covering more than 3000km) on the virioplankton distribution in epi-, meso- and bathypelagic waters in 19 areas of the Mediterranean Sea, from the Alboran Sea and Western Mediterranean, to the Tyrrhenian Sea, Sicily Channel and Ionian Sea. Integrated viral abundance in epipelagic waters was significantly higher than in deep-sea waters (on average, 2.4 vs. 0.5x10.sup.12 virusesm.sup.-3). However, abundance of viruses in the deep-Mediterranean waters was the highest reported so far for deep seas worldwide (7.0 and 3.1x10.sup.11 virusesm.sup.-3 in mesopelagic and bathypelagic waters, respectively) and their biomass accounted for 13-18% of total prokaryotic C biomass. The significant relationship between viral abundance and prokaryotic abundance and production in deep waters suggests that also deep-sea viruses are closely dependent on the abundance and metabolism of their hosts. Moreover, virus to prokaryote (and nucleoid-containing cell (NuCC)) abundance ratio increased with increasing depths suggesting that deep waters may represent optimal environments for viral survival or proliferation. Overall, our results indicate that deep waters may represent a significant reservoir of viruses and open new perspectives for future investigations of viral impact on the functioning of meso-bathypelagic ecosystems. Author Affiliation: (a) Department of Marine Science, Polytechnic University of Marche, 60131 Ancona, Italy (b) Coastal Marine Environment Institute (IAMC)-CNR, Messina Section, Italy (c) Department of Animal Biology and Marine Ecology, University of Messina, 98166 Messina, Italy Article History: Received 25 January 2006; Revised 9 May 2007; Accepted 13 May 2007

The occurrence of cultivable fungi was investigated along the water column (25-2500 m depth) of four off-shore stations in the Mediterranean basin. An unexpected high abundance of fungi, accompanied by a scarce biodiversity, was observed up to 2500 m depth. The black yeast Hortaea werneckii, known to be one of the most salt tolerant eukaryotic organisms, was isolated for the first time from the Mediterranean Sea, and it was the dominant fungus present in seawater in almost all stations and depths, suggesting its ubiquitous distribution. Isolation of cultivable strains allowed their phylogenetic and taxonomic characterization, and demonstrated that almost all the retrieved fungal species should be considered of terrestrial origin, but well adapted to survive and reproduce at temperature and salinity conditions of the Mediterranean seawater. [ABSTRACT FROM AUTHOR]

The Mediterranean sponge Halichondria (Halichondria) panicea was explored as a novel matrix for the isolation of biosurfactant‐producing bacteria. A total of 38 (out of 56) isolates gave a good response to the employed screening tests (e.g., stable emulsion detection, surface tension measurement, hemolytic activity, and blue agar plate assay) and were selected for further analyses. The thin layer chromatography revealed a possible glucidic composition of biosurfactants. Most promising strains, i.e., those able to produce stable emulsion with percentage higher than 30% and yellow spots on TLC plates, were affiliated to the genera Pseudovibrio, Acinetobacter, and Bacillus. The biosurfactant production by two isolates (i.e., Acinetobacter sp. SpN134 and Pseudovibrio sp. SpE85) was evaluated under different culture conditions, in terms of temperature, NaCl concentration, and pH. Surface tension reduction ability was more stable than the emulsification, and resulted differently influenced by salinity, temperature, and pH. Acinetobacter sp. SpN134 resulted particularly efficient and competitive if compared with other well‐known biosurfactant producers. Data suggest that sponges may represent a promising matrix for the isolation of biosurfactant‐producing bacteria, reinforcing the growing interest towards filter‐feeding organisms as underexplored sources of specialized bacteria. [ABSTRACT FROM AUTHOR]