• Beta Proteobacteria
• Straight rods occurring in chains within sheath
• Average cell is 0.6-1.4 X 1-12 um
• Motile swarmer cells have single polar flagellum
• Resting stages are not known
• Gram negative
• Able to oxidize iron and manganese
• Ferric and Manganic oxides deposited upon sheaths
• Chemoorganotrophs
• Metabolism is respiratory, never fermentative
• Percent G/C ranges from 70-71

The picture above is of colonized Leptothrix discophora taken from the undersides of water lilies.

In favorable conditions the organisms exhibit vegetative growth within a filament.  The filaments form long, cell packed sheaths that may appear yellow, dark brown to colorless.  Under certain conditions the organism forms filamentous swarmer cells.  The sheathed bacteria are common in aquatic habitats that contain increased amounts of organic matter.  Capable of  oxidizing both iron(II) and manganese(II), but are not known to receive energy from the process.  Due to products of the oxidative reaction the sheaths of the bacteria may become coated with ferric hydroxide and manganese oxide.  The precipitation usually occurs when these metals are chelated to organic substances, the precipitate is added to the sheath while the organic constituents are uptaken.

The ability to oxidize manganese distinguishes Leptothrix from other sheathed bacteria genera that do not have this capability.  The exergenic oxidizing reaction is found coupled with energy yielding reactions.  Studies have indicated the protein responsible for manganese oxidation resides in the sheath of the bacteria and not internally.  It is not clear as to why Leptothrix oxidizes manganese but is thought to occur for energetic benefits or to release organic nutrients for growth through the reaction of Mn +4 with humic and fulvic acids.

The picture above illustrates iron and manganese oxide precipitants deposited on filaments.

Certain specific media cultures have been devised for growth and isolation of Leptothrix species.  There are other medium for cultivation and maintenance of specific species.  The medium utilizes  iron and manganese compounds such as manganese bicarbonate.  

The bacteria may be found in a wide range of aquatic environments.  It exists at temperatures between 10-35 degrees Celsius, with an optimal pH range of 6.5-7.5.  The ability to precipitate metals on to their sheaths may be useful in the capture of low grade metal ore.  Some species inhabit areas within wastewater treatment facilities where they may be problematic due to clogging of parts in the system.

The above picture shows Leptothrix cholodnii being colonized by Sidercapsa ef. treubii taken from scrapings of plant roots.

Atlas, Ronald M., and Parks, Lawerence C.  Handbook of Microbiological Media.  CRC Press,  Boca Raton, FL.  501-502 pp.,  1993.

Holt, John G., et al.  Bergy's Manual of Determinative Bacteriology.  9th ed. Williams & Wilkins.  Baltimore, MD.  477-482 pp.,   1994.

Madigan, Micheal T., John M. Martinko, Jack Parker.  Brock-Biology of Microorganisms.  Prentice Hall.  Upper Saddle River, NJ.  489-491 pp.,  1984.

5. Other Related Sites on Leptothrix

Bacteria:  The Proteobacteria.   A chapter from Prescott, Harley, and Klein that give information of proteobacterium  including Leptothrix.

Iron Bacteria.  A USGS site that has photographs of injection wells clogged by Leptothrix species.

Slide Presentation on Iron Bacteria.  The site contains photographs and information on Leptothrix species.