Biol/CSES 4684

NITROBACTER

SOIL MICROBIOLOGY

Webpage Created by Larry Starkey

1. IDENTIFYING CHARACTERISTICS

Aerobic, but can be grow by anaerobic respiration.
Rod-shaped, pear-shaped/pleomorphic rods.
0.5-0.8 um x 1.0-2.0 um in size.
Cells stain Gram negative.
Species can be either motile or nonmotile.
Nitrite-oxidizing.
Facultative lithoautotrophs.
Mixotrophic growth is possible.
Catalase positive.
Unicellular with abilities to form microcolonies that consist of loosely associated cells.
Polar flattened vesicles apparent in cells.

This image shows the result of some preliminary work with two fluorescently labeled DNA probes. The Nitrobacter probe gives red fluorescence while the Nitrosomonas probe gives green fluorescence.

2. TAXONOMIC DESCRIPTION
Nitrobacter is a member of the Purple Bacteria. The organism uses nitrite as an electron donor, thereby reducing the compound to ammonia. Pear-or Rod-shaped cells with buds are apparent when grown chemolithotrophically. Under heterotrophic conditions, cells divide by either binary fission or budding. Growth is often unbalanced. This results in a large increase of poly-beta hydroxybutyrate inclusions which distort the shapes and size of the cells.

The cells of Nitrobacter are Gram negative. The outermost layer is less electron dense than the inner layers. The cytoplasmic membranes infold into the cytoplasm, forming a polar cap of intracytoplasmic membranes composed of 4-6 layers of paired membranes. These layers are missing in the budding regions.

Nitrobacter cells are facultative chemolithotrophs. When grown this way, Their energy and carbon needs are fulfilled by the oxidation of nitrite to ammonia and by fixation of carbon dioxide.

The above image is actually Nitrosococcus, but it clearly shows the internal cytoplasmic membranes.

3. ADDITIONAL SOURCES OF INFORMATION
Sprent, J.I. 1987. The Ecology of the Nitrogen Cycle. Cambridge University Press, Cambridge. 151 pp.

Vlassak, K. 1990. Nitrogen Mineralization and Nitrogen Cycling. K.U. Leuven. 180 pp.

Paul, E.A., Clark, F.E. 1996. Soil Microbiology and Biochemistry. Second Edition. Academic Press. San Diego. 340 pp.

Holt, J.G., N.R. Krieg, P.H.A. Sneath, J.T. Staley, and S.T. Williams. 1994. Bergey's Manual of Determinative Bacteriology. Ninth Edition. Williams and Wilkins. Baltimore, Maryland. 787 pp.

5. LINKS TO OTHER SITES ON NITROBACTER
MICROBIAL ZOO A link to description of organisms

LASER IMAGES These images are the result of some preliminary work with two fluorescently labeled DNA probes. The Nitrobacter probe gives red fluorescence while the Nitrosomonas probe gives green fluorescence.

NITROGEN CYCLE This picture shows an aquatic version of the nitogen cycle.

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