Nitrobacter hamburgensis

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A Microbial Biorealm page on the genus Nitrobacter hamburgensis

Classification

Bacteria; Proteobacteria; Alphaproteobacteria; Rhizobiales; Bradyrhizobiaceae; Nitrobacter; Nitrobacter hamburgensis (1)

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. 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 m in size. They are 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. (2) The bacteria have an enzyme capable of oxidizing nitrite (3). This is why it is important to sequence the genome of N. hamburgensis.

Genome structure

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. (1)

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. (3)

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

This organism produces nitrite oxidoreductase used for oxidizing nitrite to nitrate. From the redox reaction; the organism gains energy. (3)

Current Research

This section summarizes some of the current research on nitrobacter hamburgensis. While this organism has long-been described, this species in particular has not sparked current research interest. After exhausting my resources I was only able to find two articles about nitrobacter hamburgensis that were recently published. The other two articles are about nitrobacter species in general.

Recent research has investigated the benefits of using nitrifying 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. (4)

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. (5)

Going along the lines of neutralizing wastewaters, nitrobacter and another nitrifying bacteria have been found in the Seine River in France. Agricultural and urban pollution result in high concentrations of nitrogen in the Seine River and hence in the waster water treatment plants downstream of the river. Scientists here, have identified nitrobacter as one of the bacteria responsible for oxidizing nitrite products upstream of the plant (in the freshwater). Nitrobacter was also found as the main bacteria in the waste water effluents. The overall result is nitrified waste water that flows into the sea. (6)

The final research I will summarize describes the quorum sensing of nitrobacter bacteria. Quorum sensing is a term used to define a feature of bacteria that requires a certain number of them for something to happen. For example, researchers have discovered that nitrobacter can oxidize nitrite in soil which has been exposed to diesel fuel for a long period of time. They found that a large population of the bacteria is required for the nitrification to take place. (7)

References

1. www.ncbi.nlm.nih.gov/genomes/lproks.cgi

2. E. Bock et al. 1983. “New facultative lithoautotrophic nitrite-oxidizing bacteria.” Archives of Microbiology, vol. 136, no.4. (281-284)

3. 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)

4. 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)

5. 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 nitrobacter species." Current Microbiology, vol 53, no 3. (255-257)

6. Aurelie Cebron and Josette Garnier. 2005. "Nitrobacter and Nitrospira genera as representatives of nitrite-oxidizing bacteria: Detection, quantification and growth along the lower Seine River (France)." Water Research, vol 39, no 20. (4979-92)

7. Deni J and Penninckx MJ. 2004. "Influence of long-term diesel fuel pollution on nitrite-oxidizing activity and population size of nitrobacter spp in soil." Microbiol Res, vol 159, no 4. (323-329) Edited by Rashonda Butler student of Rachel Larsen and Kit Pogliano