Nitrate reducing bacterial activity in concrete cells of nuclear waste disposal

Leaching experiments of solid matrices (bitumen and cement pastes) have been first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface (see the paper of Bertron et al.). Of course, as might be suspected, the cement matrix imposes highly alkaline pH conditions (10 < pH < 11). The screening of a range of anaerobic denitrifying bacterial strains led us to select Halomonas desiderata as a model bacterium capable of catalyzing the reaction of nitrate reduction in these extreme conditions of pH. The denitrifying activity of Halomonas desiderata was quantified in batch bioreactor in the presence of solid matrices and / or leachate from bitumen and cement matrices. Denitrification was relatively fast in the presence of cement matrix (< 100 hours) and 2 to 3 times slower in the presence of bituminous matrix. Overall, the presence of solid cement promoted the kinetics of denitrification. The observation of solid surfaces at the end of the experiment revealed the presence of a biofilm of Halomonas desiderata on the cement paste surface. These attached bacteria showed a denitrifying activity comparable to planktonic bacterial culture. On the other side, no colonization of bitumen could be highlighted as either by SEM or epifluorescence microscopy. Now, we are currently developing a continuous experimental bioreactor which should allow us a more rational understanding of the bitumen-cement-microbe interactions

First record of little sleeper shark, Somniosus rostratus (Elasmobranchii: Squaliformes: Somniosidae), from the Tunisian coast, central Mediterranean Sea

The first record of the little sleeper shark, Somniosus rostratus (Risso, 1827), from the Tunisian coast, is presented in this note. It was an adult female measuring 990 mm total length and weighing 4500 g. The capture occurred off Ras Jebel located in north-eastern Tunisia at a depth of 120 m. The specimen is herein described including morphological measurements, color, and dental formula. Due to a lack of records, the real status of the species in the Mediterranean Sea remains questionable. Somniosus rostratus is rarely caught in this sea because it lives in deep bottoms poorly exploited by commercial vessels. However, recent captures of specimens and occurrence of nursery grounds suggest that a viable population of S. rostratus is probably established in this sea

First record of Physiculus dalwigki (Actinopterygii: Gadiformes: Moridae) from the Tunisian coast (central Mediterranean Sea)

A specimen of Physiculus dalwigki Kaup, 1758 measuring 218 mm in total length, 190 mm in standard length, and weighing 90 g was caught off the northern Tunisian coast. This capture constitutes the first record of this fish from the Tunisian coast. The specimen is described including morphological measurements, meristic counts, and color. Due to a lack of records, the real status of the species in the Tunisian waters still remains questionable. Physiculus dalwigki occurs only off northern Spain and south to the Strait of Gibraltar in the waters surrounding Madera and the Azores Islands, and in the Mediterranean Sea from Nice (southern France) to the Tunisian coast. Therefore, it appears that P. dalwigki is displaying a disjoint distribution with the exclusion of a large western region of the Mediterranean Sea