Shewanella amazonensis was isolated from shallow-water marine deposits derived largely from the Amazon River delta off the Amapá coast of Brazil.   The Amazon River delta is one of the major sediment depocentres on Earth (3-6% of global riverine sediment supply), and is characterized by unusually extensive zones of sedimentary Fe and Mn cycling. The upper 1±2 m of delta topset deposits, encompassing a mass of 20-30 x 10 9 metric tonnes of sediment, are dominated by non-sulfidic, suboxic redox conditions, with pore-water-dissolved Fe 2+ concentrations typically ranging from 0.1 - 1 mM. Strain SB2BT was isolated from Amazonian shelf coastal muds, and is a highly active reducer of iron and manganese oxides, thiosulfate and elemental sulfur.   Conventional phenotypic and chemotaxonomic analyses identified strain SB2BT as S . putrefaciens .   However, PCR probes designed to recognize S . putrefaciens based on gyrB (encoding the B subunit of DNA gyrase, topoisomerase II) failed to generate a specific amplicon for SB2BT, indicatting that this strain may represent a new species.   To elucidate the phylogenetic status of SB2BT, its 16S rDNA and gyrB gene sequences were analysed.   Both sequences differ from all known shewanellae, suggesting that the organism does indeed deserve the status of new species.

Shewanella amazonensis (ama.zo.nen.sis. M.L. n. amazonensis named after the area from which the bacterium was collected).   Cells of the type strain are rod-shaped, 2-3 µm in length and 0.4-0.7 µm in diameter, Gram-negative, facultatively anaerobic, polarly flagellated. No endospores nor capsules are formed. Peritrichous flagellation is not observed when the organism is cultivated on solid media. Colonies on LB agar medium are circular, smooth and convex with an entire edge, and beige to pinkish depending on the age of the colonies.   Cells are able to grow at mesophilic temperatures.   Optimal growth is observed at 37 °C. Denitrifies nitrate to nitrite and nitrite to N 2 . Exhibits cytochrome oxidase, catalase and gelatinase activity, and produces hydrogen sulfide from thiosulfate.   Haemolyses sheep blood cells and does not grow at NaCl concentrations above 3%.   Utilizes acetate, succinate, fumarate and citrate as sole carbon sources as well as a few carbohydrates and amino acids.   Very active in the reduction of iron, manganese and sulfur compounds.   Strain SB2BT was isolated from intertidal sediments.   The G+C content of the DNA is 51.7 mol%.   The type strain, SB2BT, has been deposited with the American Type Culture Collection as ATCC 700329T.

1. Venkateswaran, K., M. E. Dollhopf, R. Aller, E. Stackebrandt, and K. H. Nealson. 1998. Shewanella amazonensis sp. nov., a novel metal-reducing facultative anaerobe from Amazonian shelf muds. International Journal of Systematic Bacteriology 48: 965-972.