1. IDENTIFYING CHARACTERISTICS

• Anoxygenic phototrophic.
• Anaerobic or microaerophilic.
• Cell stains are Gram negative.
• 2 to 40 micro-meters in size.
• May be motile (motile species are polarly flagellate).
• Rods, cocci, and pleomorphic.
• Red, brown, purple, and orange pigments expressed.
• Yellow and red carotenoids.
• Bacteriochlorophylls a and b.
• Hydrogen sulfide primary electrod donor.
• Oxidation of reduced sulfur forms similar to chemoautotrophic respiratory oxidation.
• All can photoassimilate some organic compounds, such as acetate.
• Non spore-forming.
• The percent G+C ranges from 45 to 70%.
• Primarily intracellular sulfur granule deposits.
• Some possess prominent gas vacuoles.
• Some require vitamin B12 as an organic growth factor.

The above pictures, respectively, show Chromatium vinosum (x1400), Thispirillum jenense (x1190) (notice the polar flagella), and Thiopedia rosea (x1400) (notice the prominent gas vacuoles).

2. TAXONOMIC DESCRIPTION

The Chromatiacaea are generally referred to as "purple sulfur bacteria." The result of oxidation of hydrogen sulfide is elemental sulfur, which is stored intracellularly, except for Ectothiorhodospira, which permits extracellular deposits of sulfur. This elemental sulfur is oxidized to sulfuric acid for the attainment of energy. They are capable of using thiosulfate, and a few can use organic compounds, such as lower weight fatty acids, as the hydrogen donor. Obviously, these bacteria photosynthesize. Therefore, light is required to drive their photosynthetic reactions. Some have been able to grow in a chemoautotrophic fashion with small amounts of oxygen present. One, Thiocapsa, can grow chemotrophically in a fully oxygenated environment.

The picture to the left shows C. vinosum.

With the name inclusive "purple," pigment is common. The combination of the yellow and red carotenoids with the bacteriochlorophylls a and b form colors of red, brown, purple and sometimes orange. These bacteria are not uncommon inhabitants of freshwater, and sometimes marine environments, thriving on primarily anaerobic locations. They are commonly found in sulfur springs and stagnating aqueous environments where hydrogen sulfide can be easily used.


The picture to the left shows Thiospirillum jenense.

Frobisher, Martin, Sc.D. Fundamentals of Microbiology: Ninth Ed. W.B. Saunders Co.: Philladelphia, PA. 1974. p.460-465.

Paul, E.A. and Clark, F.E. Soil Microbiology and Biochemistry: Second Edition Academic Press: New York. 1996. p. 74 & 75.

Pelczar, Michael J., Jr. Microbiology. McGraw-Hill Book Company: New York. 1977. p.245.

Stanier, Roger Y. The Microbial World: Fifth Ed. Prentice-Hall: Englewood Cliffs, NJ. 1986. p. 374-375.

Chromatiacaea, the fancy name for Purple Sulfur Bacteria

Purple Sulfur Bacteria

Yes, more Purple Sulfur Bacteria