Viruses, prokaryotes and DNA in the sediments of a deep-hypersaline anoxic basin (DHAB) of the Mediterranean Sea.

Viral and prokaryote abundance were investigated in a deep-hypersaline anoxic basin of the Eastern Mediterranean Sea (DHAB Atalante basin at c. 3000 m depth). This system was compared with two nearby deep-sea sites characterized by oxic conditions. Viral abundance and virus to prokaryote abundance ratio in hypersaline anoxic sediments displayed values close to those reported in oxic sites. The analysis of vertical profiles of viral abundance in the Atalante basin revealed the lack of significant changes with depth in the sediment, suggesting that benthic viruses in these anoxic and hypersaline conditions are preserved or resistant to decay. The anoxic basin displayed also very high concentrations of labile organic components (proteins and lipids) and extracellular DNA. These findings suggest that the DHAB sediments represent a reservoir for long-term preservation of benthic viruses and nucleic acids.

Aromatic hydrocarbon degradation patterns and catechol 2,3-dioxygenase genes in microbial cultures from deep anoxic hypersaline lakes in the eastern Mediterranean sea.

Several mixed cultures able to grow on different aromatic hydrocarbons were obtained from different depths (between 3500 and 3660 m under the sea surface) of water/brine interfaces (1 to 5 m over the estimated brine surface) of three deep hypersaline anoxic basins (Urania, Discovery and Atalante) in the eastern Mediterranean sea. Eight strains which completely removed toluene from the medium in six to 10 days were isolated from one of the mixed cultures obtained from the Urania basin. The strains grew on toluene and yeast extract in the presence of NaCl concentrations of up to 50 and 100 g l(-1), respectively, indicating that they are halotolerant rather than halophilic. Even though DNA fingerprinting methods showed that the strains were strictly related, two groups could be found on the basis of the plasmid profile. Metabolic profiling and partial sequencing (350 bp) of the 16S rDNA showed that the strains were related to Pseudomonas mendocina. A 320 bp fragment of the catechol 2,3-dioxygenase gene from all the strains was aimplified by PCR. The sequence of the fragment showed 100% identity with xylE from pWW53 of Pseudomonas putida MT53 isolated from soil. Southern hybridisation experiments showed that catechol 2,3-dioxygenase is plasmid encoded.