Shewanella amazonensis sp. nov., a novel metal-reducing facultative anaerobe from Amazonian shelf muds

A new bacterial species belonging to the genus Shewanella is described on the basis of phenotypic characterization and sequence analysis of its 165 rRNA-encoding and gyrase B (gyrB) genes. This organism, isolated from shallow-water marine sediments derived from the Amazon River delta, is a Gram-negative, motile, polarly flagellated, facultatively anaerobic, rod- shaped eubacterium and has a G+C content of 51.7 mol%. Strain SB2B(T) is exceptionally active in the anaerobic reduction of iron, manganese and sulfur compounds. SB2B(T) grows optimally at 35 °C, with 1-3% NaCl and over a pH range of 7-8. Analysis of the 165 rDNA sequence revealed a clear affiliation between strain SB2B(T) 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 SB2B(T) and its phylogenetically closest relatives revealed low similarity values (24.6-42.7%) which indicated species status for strain SB2B(T). That SB2B(T) 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 SB2B(T) (= ATCC 700329(T)) is designated as the type strain.