Alishewanella fetalis

Alishewanella fetalis
A. fetalis grown on a BHI agar plate visualized by transmission electron microscopy
Scientific classification
Domain:	Bacteria
Phylum:	Proteobacteria
Class:	Gammaproteobacteria
Order:	Alteromonadales
Family:	Alteromonadaceae
Genus:	Alishewanella
Species:	fetalis

The genus Alishewanella is one of the major branches of the family Alteromonadaceae. It was proposed to accommodate A. fetalis, isolated from an autopsy of a human fetus, in 2000.^[1] In 2009, A. aestuarii was isolated from tidal flat sediment and indicated as being a representative of Alishewanella.^[2] The third Alishewanella species was isolated from gajami sikhae, a Korean fermented food, in 2009 and was given the name A. jeotgali.^[1] Most recently, in 2010, the fourth currently isolated species of Alishewanella, A. agri, was isolated from landfill soil in Korea.^[3] Currently these are the only four isolated and characterized species of the genus Alishewanella.

Identification

Alishewanella fetalis is a Gram-negative, non-motile, facultatively anaerobic, rod-shaped bacterium. These rods are about 2 μm in length and 0.5-1 μm in width. They typically occur as a single cell.^[4] It was initially mislabelled as Shewanella putrefaciens, previously known as Pseudomonas putrefaciens, due to the presence of similar fatty acids^[4] in its membrane lipids. However, after further evaluation, it was found that this was a novel species. Due to the relatedness to Shewanella, the genus was named Alishewanella. Also, having been initially isolated from an autopsy of a human fetus in 1992 in Sweden, it was given the species name fetalis.^[4]

Growth

A. fetalis grows at temperatures between 25° and 42°C, with optimum growth at 37°C. It cannot grow below 20°C.^[4] It is facultatively anaerobic and can utilize electron acceptors such as trimethylamine oxide (TMAO), nitrate, nitrite, and thiosulphate, but not sulphite or ferric iron.^[5] It is not only halotolerant, but requires NaCl for growth. NaCl concentrations of up to 8%, but not 10% are tolerated.^[4] A. fetalis is oxidase- and catalase-positive but does not produce indole and β-galactosidase. It cannot ferment carbohydrates.^[4] By these results, A. fetalis is very closely related to both Shewanella putrefaciens and Shewanella algae.^[4] However, A. fetalis differs from the Shewanella genus by the ability to produce H₂S.^[4]

Genome

Studies of A. fetalis show that the GC content of the genome is 50.6%,^[5] which differs greatly from that of Shewanella putrefaciens, with a GC content of 42-47%.^[4] It shows a relationship to both Rheinheimara baltica through 16S rRNA,^[5] and to the family Vibrionaceae through gyrase B.^[4] With regards to other Alishewanella species, A. fetalis is closely related to Alishewanella jeotgali (98.04%),^[1] Alishewanella aestuarii (98.3%),^[2] and Alishewanella agri (98.7%)^[3] by 16S rRNA.

References