BIOL/CSES 4684

NOCARDIA

SOIL MICROBIOLOGY

This webpage was created by COURTNEY McCOMBS

1. IDENTIFYING CHARACTERISTICS

Strictly aerobic.
No motile elements produced.
0.5-1.2 um in size.
mDAP major constituent of cell wall.
Cells stain Gram positive to Gram variable.
Chemoorganotrophic.
High G + C percent ( 64 -72).
Rudimentary to extensively branched hyphae.
Mesophilic.
Catalase positive.
Actinomycete.
Type IV cell wall.
Nocardiomycolic acid produced.
Widely distributed and abundant in soils.

The picture to the left shows a typical Nocardia colony.

2. TAXONOMIC DESCRIPTION

The genus Nocardia is largely defined on the basis of cell envelope lipid and peptidoglycan composition. Contain lipid LCN - A and nocardiomycolic acids. They are not motile. Aerial mycelium is produced, and can be almost non-existent to completely covering the substrate mycelium with a white-pigmented aerial hyphae. Rudimentary to extensively branched vegetative hyphae, ranging from 0.5-1.2 micrometers in diameter, which often fragments into bacteroid, rod-shaped to coccoid elements. Metabolism is strictly aerobic. They are mesophilic and chemoorganotrophic, and resistant to lysozyme. Can form acid from glucose, fructose, and glycerol oxidativeely. Can utilize sodium acetate, n-butyrate, H-malate, propionate, pyruvate, succinate, and paraffins as sole sources of carbon for growth. The genus is composed of saprophytes that can utilize a wide range of organic compounds. There are no autotrophs. Currently 12 species of Nocardia are recognized, although the number of species has been larger in the past. The type species is N. asteroides.

The above picture shows Nocardia (see arrow) being phagocytized by an immune system cell.

3. ISOLATION AND ECOLOGY

Most nocardia grow readily on a variety of media containing nitrogen sources that include ammonium, nitrates, and amino acids. They also grow on more complex substances such as soy, meat, yeast peptones and hydrolysates. Glucose, acetate and propionate are good carbon sources. They grow at temperatures ranging from 15-37* C. Some can grow at higher temperatures and some considerably lower. Some strains grow to colonies in 3-7 days, while others take much longer. Once isolated, the nocardia are not difficult to grow. N. asteroides can be isolated and enhanced with selective media, and will have a pink to red substrate mycelium covered with white aerial hyphae.

Widely distributed in soils, water, air, and sewage. Can be pathogenic to birds, goats, cats, dogs, fish, horses, and even people. Usually infections in people occur after their immune system has been compromised because of some other disease, like AIDS. N. asteroides is usually blamed for human infections. N. vaccinni is pathogenic to blueberries.

The above picture shows a transmission electron microscope image of Nocardia (N) in a lymphocyte cell.

4. ADDITIONAL SOURCES OF INFORMATION

Goodfellow, M., G. H. Brownell, J. A. Serrano, ed., 1976. The Biology of Nocardia, Academic Press, New York.

Holt, J. G., N. R. Kreig, P. H. A. Sneath, J. T. Stanley, and S. T. Williams. 1994. Bergy's Manual of Determinative Bacteriology. Ninth Edition. Williams and Wilkins. Baltimore, Maryland.

Mordarski, M., W. Kurylowicz, J. Jeljaszewicz, ed., 1978. Nocardia and Streptomyces, Proceedings of the International Symposium on Nocardia and Streptomyces, New York.

Sykes, G., F. A. Skinner, ed., 1973. Actinomycetes: Characteristics and Practical Importance, Academic Press, New York.