Shewanella amazonensis
A Microbial Biorealm page on the genus Shewanella amazonensis
Classification
Higher order taxa
Bacteria (Domain); Proteobacteria (Phylum); Gammaproteobacteria (Class); Alteromonadales (Order); Shewanellaceae (Family); Shewanella (Genus)
Species
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NCBI: Taxonomy |
Shewanella amazonensis
Description and significance
Shewanella amazonensis (strain ATC BAA-1098/SB2B) is a Gram-negative, facultatively anaerobic, motile, polarly flagellated, rod-shaped eubacterium. It is exceptionally active in the anaerobic reduction of iron, manganese and sulfur compounds. It was isolated from shelf coastal muds, in intertidal sediments in the Amazon River delta, off the Amapá coast of Brazil.
Genome structure
Analysis of the 16S rDNA sequence revealed a clear affiliation between strain SB2BT and members of the gamma subclass of the class Proteobacteria. High similarity values were found with certain members of the genus Shewanella, especially with Shewanella putrefaciens, and this was supported by cellular fatty acid profiles and phenotypic characterization. DNA–DNA hybridization between strain SB2BT and its phylogenetically closest relatives revealed low similarity values (24<6–42<7%) which indicated species status for strain SB2BT. That SB2BT represents a distinct bacterial species within the genus Shewanella is also supported by gyrB sequence analysis. Considering the source of the isolate, the name Shewanella amazonensis sp. nov. is proposed and strain SB2BT (ATCC 700329T) is designated as the type strain.
Cell structure and metabolism
Shewanella amazonensis SB2B 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 N2. 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.
Ecology
Shewanella amazonensis was isolated from shelf coastal muds, in intertidal sediments in the Amazon River delta, off the Amapá coast of Brazil. It is able to grow at mesophilic temperatures with optimal growth at 37°C and over a pH range of 6-9 with optimum at 7-8. Growth is seen in the absence of NaCl, but growth yield is high in 1% NaCl. The Amazon River delta is one of the major sediment depocentres on Earth (~3-6% of global riverine sediment supply), and is characterized by unusally extensive zones of sedimentary Fe and Mn cycling. The upper 1-2 m of delta topset deposits, encompassing a mass of 20-30x109 metric tons of sediment, are dominated by non-sulfidic, suboxic redox conditions, with pore-water-dissolved Fe2+ concentrations typically ranging from ~ 0.1-1 mM. Samples from the seasonally mobile intertidal deposits at the initiation of this coastal system south of Cabo Cassiporé were obtained for the present study. Shewanella amazonensis is a highly active reducer of iron and manganese oxides, thiosulfate and elemental sulfur. Denitrifies nitrate to nitrite and nitrite to N2. 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.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
