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The composition of ammonia-oxidizing bacteria from the ␤-Proteobacteria subclass (␤AOB) was studied in the surface and upper-oxycline oxic waters (2-to 50-m depth, ϳ200 to 44 M O 2 ) and within the oxygen minimum zone (OMZ) suboxic waters (50-to 400-m depth, <10 M O 2 ) of the eastern South Pacific off northern Chile. This study was carried out through cloning and sequencing of genes coding for 16S rRNA and the ammonia monooxygenase enzyme active subunit (amoA). Sequences affiliated with Nitrosospiralike cluster 1 dominated the 16S rRNA gene clone libraries constructed from both oxic and suboxic waters. Cluster 1 consists exclusively of yet-uncultivated ␤AOB from marine environments. However, a single clone, out of 224 obtained from the OMZ, was found to belong to Nitrosospira lineage cluster 0. To our knowledge, cluster 0 sequences have been derived from ␤AOB isolated only from sand, soil, and freshwater environments. Sequences in clone libraries of the amoA gene from the surface and upper oxycline could be grouped in a marine subcluster, also containing no cultured representatives. In contrast, all 74 amoA sequences originating from the OMZ were either closely affiliated with cultured Nitrosospira spp. from clusters 0 and 2 or with other yet-uncultured ␤AOB from soil and an aerated-anoxic Orbal process waste treatment plant. Our results reveal the presence of Nitrosospira-like ␤AOB in both oxic and suboxic waters associated with the OMZ but with a clear community shift at the functional level (amoA) along the strong oxygen gradient.Oxygen minimum zones (OMZs) are permanent areas of the ocean with dissolved O 2 concentrations of Յ22 M at intermediate depths (15, 18) caused by low rates of ventilation and high biological O 2 demand. The main zones are found in the eastern tropical Pacific and Arabian Sea. Associated with a sharp decrease of dissolved O 2 concentration with depth is an intense nitrogen cycle that generates characteristic vertical distributions of nitrogen compounds within the OMZ: i.e., high NO 3 Ϫ deficit, a secondary nitrite maximum, and low NH 4 ϩ concentrations are found within the core, as well as N 2 O maxima towards the OMZ boundaries (8,26,30,41). Such strong chemical gradients produced by OMZs could be considered as gene flow barriers and their oxygen-deficient waters as suitable environments for innovation, where organisms develop specific adaptations to exploit these unique conditions (9, 30, 42). In fact, novel and yet-uncultivated groups of denitrifiers have been found in the OMZ of the Arabian Sea (17a) and the eastern South Pacific (6a) by cloning and sequencing of the nirS genes. However, the diversity of most of the OMZ microbial world remains unexplored. Ammonia-oxidizing bacteria (AOB) are considered to play a key role in the nitrogen cycling of these OMZs, contributing to NH 4 ϩ removal and NO 2 Ϫ and N 2 O production (26, 33, 52).AOB consist of a group of chemolithoautotrophic microorganisms able to oxidize aerobically NH 4 ϩ to NO 2 Ϫ , via NH 2 OH (hydroxylamine), a dissimi...

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm −3 NaCl) and mesophilic (37• C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm −3 and 1572 mg dm

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The ability of the human isolate Lactobacillus fermentum UCO-979C to form biofilm and synthesize exopolysaccharide on abiotic and biotic models is described. These properties were compared with the well-known Lactobacillus casei Shirota to better understand their anti-Helicobacter pylori probiotic activities. The two strains of lactobacilli synthesized exopolysaccharide as detected by the Dubois method and formed biofilm on abiotic and biotic surfaces visualized by crystal violet staining and scanning electron microscopy. Concomitantly, these strains inhibited H. pylori urease activity by up to 80.4% (strain UCO-979C) and 66.8% (strain Shirota) in gastric adenocarcinoma (AGS) cells, but the two species showed equal levels of inhibition (~84%) in colorectal adenocarcinoma (Caco-2) cells. The results suggest that L. fermentum UCO-979C has probiotic potential against H. pylori infections. However, further analyses are needed to explain the increased activity observed against the pathogen in AGS cells as compared to L. casei Shirota.

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Emissions of hydrogen sulfide (H