Micrococcus

SOIL MICROBIOLOGY

BIOL/CSES 4684

1. IDENTIFYING CHARACTERISTICS

• cell shape is sperical
• 0.5-2.0µm in diameter
• cells occur in pairs,tetrads or irregular clusters, not chains
• gram positive
• seldom motlie, non sporing
• strictly aerobic
• colonies usually pigmented in shades of yellow or red
• chemoorganotrophs with respiratory metabolism
• catalase positive
• usually halotolerant, grow with 5% NaCl
• resistant to lysostaphin
• optimum growth temperature 25-37°C, but some species are pyschrophiles
• high GC
• DNA (mol %GC) 66-73
• Occur primarily on mammalian skin and in soil, but are commonly isolated from food products and air.

The above photograph is Mirococcus gram stained positive

2. TAXONOMIC DESCRIPTION

Micrococcus falls into the gram positive cocci group. This group is made up of spherical or slightly oval cells and stain gram positive. Gram positive cocci do not produce endospores and motility is uncommon. Gram positive cocci fall into distinct grouping of aerobic, facultatviely anaerobic and strictly anaerobic genera. Gram positive cocci are relatively resistant to reduced water potiental and tolerate drying and high salt concentrations fairly well.

Micrococcus is an aerobic organism with a typical respiratory metabolism. They are catalase-positive, which helps distinguish them from Streptococcus and other genera of gram positive cocci. Micrococcus can also be seperated from Staphylococcus and other gram positive cocci based upon the oxidation-fermentation test. Micrococcus is an obligate aerobe and produces acid from glucose only.

Characteristics that identify Micrococcus from other gram-positive cocci

• Micrococcus cells are predominately arranaged as clusters, tetrads other gram-positive cocci are arranged as pairs of rods, tetrads or clumps.
• Micrococcus are not known to be motile. Many other gram-positive cocci are.
• Micrococcus are not obligate halophiles. They do not require 7.5% NaCl for growth like other gram-positive cocci do.
• Micrococcus does produce catalase like many other gram-positive cocci.
• Micrococcus have cytochromes present.
• Micrococcus often produce acidity from utilizable carbohydrates. Other gram-positive cocci either do not produce acid or their acid production is weak.

Micrococcus can also be seperated from one another based upon characteristics such as motility, oxidation tests, color of colonies when plated, optimum growth temperatures and several other laboratory tests.

3. ISOLATION AND ECOLOGY

Micrococcus will usually grow on simple media. If it is it cultured in broth or in a nutrient rich agar, like blood agar, Micrococcus colonies maybe red, yellow, white, off-white and cream colored when observed unstained. Halos of water soluble pigments ( usually yellow) around colonies are frequently seen.

Micrococcus Meduim

Composition per liter:

• Agar........................15.0g
• Peptone...................5.0g
• Yeast extract............3.0g
• Beef extract..............1.5g
• Glucose....................1.0g

pH 7.4+ or - 0.2 at 25°C

Use: For the cultivation and maintenance of Staphylococcus aureus and Micrococcus species.

Micrococcus Medium, FDA

Composition per liter:

• Agar.................................15.0g

• Proteose peptone..............10.0g

• Beef extract.......................5.0g

• NaCl.................................5.0g

pH 7.2+ or - 0.2 at 25°C

Use: For the cultivation and maintenance of Staphylococcus aureus and Micrococcus species.

Micrococcus can also be found in freshwater environments or in soil. Some strands of Micrococcus can be used for hydrocarbon and wax degradation. Others are used by the agricultural-food industry as production starters and in dietary products.

4. ADDITIONAL SOURCES OF INFORMATION

Atlas, R.M. 1993. Handbook of Microbiological Media. CRC Press. Boca Raton, Florida. 591 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. 527,530,534,542 pp.

Madigan, M.T., Martinko,J.M., Parker,J. 2000. Brock Biology of Microorganisms. Ninth Edition. Prentice Hall. New Jersey. 502-503 pp.

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