Bacteria; Proteobacteria; Alphaproteobacteria; Rhizobiales; Bradyrhizobiaceae; Nitrobacter; Nitrobacter hamburgensis
Description and significance
Nitrobacter hamburgensis, gram negative bacteria, was isolated from soil of the Old Botanic Garden in Hamburg and of a corn field in Yucatan. Two strains have been identified, the X14 strain and the Y strain. The main types of environments they inhabit are soil, building sandstone, and sewage sludge. Its cells are 0.5-0.8 x 1.2-2.0 μm in size. They are pleomorphic; mostly pear-shaped and motile via one subpolar to lateral flagellum. Intracytoplasmic membranes appear as caps of flattened vesicles or membrane vesicles in the central region of the cell. The bacteria have an enzyme capable of oxidizing nitrite. This is why it is important to sequence the genome of N. hamburgensis.
There is one circular DNA chromosome and three circular DNA plasmids. The chromosome has 4,406,967 nucleotides. Plasmid 1 has 294,829 nucleotides, 2 has 188,318 nucleotides, and 3 has 121,408 nucleotides.
Cell structure and metabolism
N. hamburgensis gains energy from oxidation of nitrite to nitrate via the enzyme nitrite oxidoreductase (NOR). It grows best mixotrophically with a doubling time of 10 hours to 18 hours. Its growth rate under heterotrophic conditions is slower than under mixotrophic conditions, but higher than under lithoautotrophic conditions.
Application to Biotechnology
This organism produces nitrite oxidoreductase used for oxidizing nitrite to nitrate. From the redox reaction; the organism gains energy.
Recent research has investigated the benefits of using nirtrifying bacteria in neutralizing wastewater. Researchers have constructed biofilms with different nitrifying bacteria including N. hamburgensis. They were successful in removing high levels of nitrogen in a short amount of time from municipal effluents from wastewater treatment plants. The biofilms are sufficient alternatives for the treatment of industrial wastewaters that otherwise requires very large and expensive reactors for efficient bioremediation of effluents.
Other current research has identified evidence that the previously published sequence of norX in N. hamburgensis X14(T) contains an invalid base "insertion," which resulted in a frameshift and a misidentified start codon.
Jens Aamand, Thomas Ahl, and Eva Spieck. 1996. "Monoclonal Antibodies Recognizing Nitirite Oxidoreductase fo Nitrobacter hamburgensis, N. winogradskyi, and N. vulgaris." Applied and Environmental Microbiology, vol. 67, no. 7. (2352-5)
E. Bock et al. 1983. “New facultative lithoautotrophic nitrite-oxidizing bacteria.” Archives of Microbiology, vol. 136, no.4. (281-284)
Franco-Rivera A, Paniaqua-Michel S, Zamora-Castro J. 2007. “Characterization and performance of constructed nitrifying biofilms during nitrogen bioremediation of a wastewater effluent.” Journal of industrial microbiology and biotechnology, vol. 34, no. 4. (279-287)
Maron PA, Coeur C, Pink C, Clays-Josserand A, Lensi R, Richaume-A Potier. 2006. “Validation of the correct start codon of norX/nxrX and universality of the norAXB/nxrAXB gene cluster in nitorbacter species. Current Microbiology, vol 53, no 3. (255-257) Edited by Rashonda Butler of UC San Diego, student of Rachel Larsen.
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