A New Facultative Chemolithotrophic Nitrifying Bacteria: Nitrobacter iranicum sp .v Nov

Phenotypic and genetic studies were performed on a Gram-negative, Oxidizing bacterium isolated from soil of a Potato field in Hamadan,Iran. The Cells were 0.4 – 0.5 X 0.8 -1.2μm in size with short rods spindle shaped and polar caps of interacytoplasmic membranes. Carboxissomes were also present .The organism grew chemolithotrophically, hetrotrophically or mixotrophically. It grew at pH range from 6.7 to 8.3 with optimum at 7.6 .The growth rate under hetrotrophic condition is slower than under mixotrophic condition, but faster than under lithotrophic condition. The DNA content was 57mol %. In the absent of oxygen growth was possible by dissimilatory nitrate reduction .The sequence of nearly complete 16S rRNA gene of the strain is recorded in the Gen Bank under number AY578913. Generation times varied from 7to 14houre. The new isolates from the soil were described as a new species of the genus Nitrobacteria,N.iranicum on the basis of their substantial morphological, physiological and genetic differences from the recognized neutrophylic representatives of this genus.