Impact of anthropogenic activities and natural inputs on oceanographic characteristics of water and geochemistry of surface sediments in different sites along the Egyptian Red Sea Coast

The surface sediments and sea water interactions were studied in five different sites along the Egyptian Red Sea coast. There are commutative and correlative relations between these constituents, therefore, any alterations occur in the sediments and sea water will be directly reflected on the marine environment. Sixty-five sediment samples were collected and also the oceanographic characteristics of surface sea water such as salinity, pH and total dissolved salts (TDS) were measured in situ for the same five localities (El-Hamrawein Harbour, Sharm el Bahari, Abu Dabab, Qola'an and Shalatein). The oceanographic properties of sea water show high salinity (42.55 and 42.59 psu) and total dissolved salts values (31.77 and 31.73 mg/L-1) in both Qola'an and Shalatein, also Abu Dabab and Qala'an areas shows high pH values (8.00 and 8.04) due to the presence of dense sea grass cover. The sediment types generally changes from sand to slightly gravelly sand or muddy sand, also the surface sediments are mainly medium sand, moderately to poorly sorted. Geochemically, the factor controlling the carbonate content of studies sediments includes material supply of biogenic and terrigenous components. Therefore, sediments of El-Hamrawein, Sharm el-Bahari, Abu Dabab and Shalatein areas are terrigenous sediments, while sediments of Qola'an area south Marsa Alam are highly carbonates. In general, organic matter (4.82%) is higher in the sediments relative to adjacent areas due to high contributions of terrestrial materials by wadis and anthropogenic factors.Key words: Grain size, geochemistry, oceanographic, sediments, seawater, Red Sea, Egypt

Azotobacter genomes: the genome of Azotobacter chroococcum NCIMB 8003 (ATCC 4412)

The genome of the soil-dwelling heterotrophic N2-fixing Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 (ATCC 4412) (Ac-8003) has been determined. It consists of 7 circular replicons totalling 5,192,291 bp comprising a circular chromosome of 4,591,803 bp and six plasmids pAcX50a, b, c, d, e, f of 10,435 bp, 13,852, 62,783, 69,713, 132,724, and 311,724 bp respectively. The chromosome has a G+C content of 66.27% and the six plasmids have G+C contents of 58.1, 55.3, 56.7, 59.2, 61.9, and 62.6% respectively. The methylome has also been determined and 5 methylation motifs have been identified. The genome also contains a very high number of transposase/inactivated transposase genes from at least 12 of the 17 recognised insertion sequence families. The Ac-8003 genome has been compared with that of Azotobacter vinelandii ATCC BAA-1303 (Av-DJ), a derivative of strain O, the only other member of the Azotobacteraceae determined so far which has a single chromosome of 5,365,318 bp and no plasmids. The chromosomes show significant stretches of synteny throughout but also reveal a history of many deletion/insertion events. The Ac-8003 genome encodes 4628 predicted protein-encoding genes of which 568 (12.2%) are plasmid borne. 3048 (65%) of these show > 85% identity to the 5050 protein-encoding genes identified in Av-DJ, and of these 99 are plasmid-borne. The core biosynthetic and metabolic pathways and macromolecular architectures and machineries of these organisms appear largely conserved including genes for CO-dehydrogenase, formate dehydrogenase and a soluble NiFe-hydrogenase. The genetic bases for many of the detailed phenotypic differences reported for these organisms have also been identified. Also many other potential phenotypic differences have been uncovered. Properties endowed by the plasmids are described including the presence of an entire aerobic corrin synthesis pathway in pAcX50f and the presence of genes for retro-conjugation in pAcX50c. All these findings are related to the potentially different environmental niches from which these organisms were isolated and to emerging theories about how microbes contribute to their communities