Shewanella amazonensis

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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

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 was isolated from shelf coastal muds, in intertidal sediments in the Amazon River delta, off the Amapá coast of Brazil. It is exceptionally active in the anaerobic reduction of iron, manganese and sulfur compounds. This ability makes Shewanella amazonensis important for bioremediation of contaminated metals and radioactive wastes.

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.

Shewanella amazonensis SB2B, complete genome DNA; circular; Length: 4,306,142 nt Replicon Type: chromosome Created: 2006/12/21 (NCBI)

Cell structure and metabolism

Shewanella amazonensis SB2B is rod-shaped, 2-3 μm in length and 0.4-0.7 μm in diameter, Gram-negative, facultatively anaerobic and motile by a single unsheathed polar flagellum. 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. Young colonies have a diameter of 1-2mm. Strain SB2B has neither diffusible pigments nor bioluminescence. Cells are able to grow at mesophilic temperatures. Optimal growth is observed at 37°C. Denitrifies nitrate to nitrite and nitrite to nitrogen gas. 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. Strain SB2B tests negative for the production of amylase, lipase, alginase, arginine dihydrolase and decarboxylases of lysine and ornithine. It is unable to ferment glucose.

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. Strain SB2B is capable of using a variety of compounds as electron acceptors, including iron, manganese, nitrate, nitrite, fumarate and thiosulfate. This ability makes it important for bioremediation of contaminated metals and radioactive wastes. Biogeochemical data have long suggested a significant role for iron and manganese reduction in global nutrient cycling.

Pathology

There is no information available on the pathology of Shewanella amazonensis. Other members of its genus have pathogenic characteristics, but cases are extremely rare. Some strains of Shewanella have been found to be the cause of gastrointestinal related afflictions. Shewanella putrifaciens, is significant in the fisheries industry due to its pathogenicity of numerous fish (Taylor et al.). Shewanella alga, in an unusual case, even caused tonsilitis in a healthy child (Liu et al.). Shewanella septicemia caused the death of an older man with a damaged liver (Otsuka et al.). Shewanella septicemia was implicated in the death of a 67 year old Japanese man as a result of a lethal sepsis in conjunction with liver failure (Otsuka T et al.). Another case details Shewanella infections following gastric lavage of a patient with gastrointestinal bleeding (Saidel-Odes et al.).

References

Copeland A., Lucas S., Lapidus A., Barry K., Detter J.C., Glavina del Rio T., Hammon N., Israni S., Dalin E., Tice H., Pitluck S., Munk A.C., Brettin T., Bruce D., Han C., Tapia R., Gilna P., Schmutz J., Larimer F., Land M., Hauser L., Kyrpides N., Mikhailova N., Fredrickson J., Richardson P. ; "Complete sequence of Shewanella amazonensis SB2B."; Submitted (DEC-2006) to the EMBL/GenBank/DDBJ databases.

"HAMAP: Shewanella amazonensis (strain ATCC BAA-1098 / SB2B) complete proteome". HAMAP. ExPASy.org. http://expasy.org/sprot/hamap/SHEAM.html Accessed October 25, 2007.

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. Reprint available at http://ijs.sgmjournals.org/cgi/reprint/48/3/965.pdf