Leptothrix

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Leptothrix
Leptothrix, cell chain in a vagina and empty vagina, light microscope image

Leptothrix , cell chain in a vagina and empty vagina, light microscope image

Systematics
Domain : Bacteria (bacteria)
Department : Proteobacteria
Class : Betaproteobacteria
Order : Burkholderiales
Family : Comamonadaceae
Genre : Leptothrix
Scientific name
Leptothrix
Kützing 1843

Leptothrix is a genus of bacteria that occurs in ferrous waters. As a special feature, these rod-shaped bacteria form tubes in which they are arranged one behind the other. They cause a noticeable precipitation of oxides or hydroxides of trivalent iron on the tubes ("iron bacteria"), which can lead to the formation of ocher and iron ores .

properties

The bacteria are straight, rod-shaped (roughly cylindrical) cells with a diameter of 0.6 to 1.5 µm and a length of 1.5 to 15 µm. They are gram-negative and at times each at one end of the cell (polar or subpolar) by a flagellum monotrich, monopolar flagellated. The species L. lopholea forms a subpolar flagella bundle, so it is polytrichal, monopolar flagellated. The bacteria sometimes swim freely ("swarmers") individually or in cell chains. Most of the time, however, they form longitudinal rows (cell chains) that are located in a tube made of organic material that is separated from them . These tubes, also known as sheaths , are made of organic polymers that form intertwined fibrils . The cells are not firmly attached to the tubes and can move around in them. Some species form mucus outside the vagina. Iron dissolved in the water of the habitat , predominantly as divalent iron ions (Fe 2+ ), accumulates after oxidation with dissolved oxygen in the vagina in the form of oxidic or hydroxidic compounds of trivalent iron and encrusts and thickens them in this way . As a reserve substance is polyhydroxybutyric acid formed, and in the form of granules deposited in the cells. The GC content of the DNA is 68-71 mol%. In contrast to the other species, a pure culture of L. ochracea has not yet succeeded.

Divorce

The sheaths of L. cholodnii consist of 6.5 nm thick fibrils, the wall thickness is 30–100 nm, on the outside there is a diffuse layer of mucus. The vagina contains 34% polysaccharides (main components: uronic acids and amino sugars ), 24% proteins , 8% lipids and 4% inorganic substances .

metabolism

The energy metabolism is strictly aerobic , oxidative , chemoorganoheterotrophic . Organic substances can only be recycled to a limited extent and slowly. Depending on the type, some sugars , glycerine and organic acids are used. Preferred nitrogen sources are amino acids , some species utilize ammonium and nitrate . Because of the oxidation of the divalent iron and the deposition of the Fe (III) compounds formed in this way on the vagina (see properties), it was assumed that this oxidation is effected enzymatically by the bacteria and that the energy released is used by the bacteria that are chemolithotrophic , possibly also autotrophic . So far this has not been proven. However, the iron oxidation and the manganese oxidation seem to be accelerated by the bacteria, even if the energy released is not used by them.

Vitamin B12 is generally required, and some types also require thiamine and biotin .

Occurrence, ecology

Leptothrix masses in a moat

Leptothrix occurs in standing or slowly flowing, neutral to slightly acidic freshwater waters with only low concentrations of organic substances and with an oxygen concentration gradient, especially in those with high concentrations of iron (dissolved as Fe 2+ ions). Examples: ditches in moors and swamps , iron springs. The incrustation of the tubes with oxidic or hydroxidic iron (III) compounds hinders the exchange of substances with the environment. The exchange of substances with the surrounding medium is ensured by the fact that the cells move out of the vaginal areas thickened in this way and next to them form new, thinner, and not yet encrusted sheaths with iron compounds. As a result, in such a body of water there are large quantities of empty, iron-encrusted tubes in conspicuous, flaky, ocher-colored masses. Microscopically, one sees in these flaky ocher masses predominantly the empty, more or less thickened tubes and only rarely bacterial cells, namely these in thin tubes.

In waters that contain dissolved, bivalent manganese (Mn 2+ ions), compounds of tetravalent manganese formed by oxidation are deposited on the vagina.

Its occurrence in sheaths has the advantage that long structures are formed in this way without the need for cell lengthening or the formation of multicellular cell threads. Long, fibrous structures enable loose, surface-rich aggregation, which favors the exchange of substances with the surrounding medium. At the same time, the vagina protects the bacteria from bacteria-eating organisms (especially protozoa ) and from bacteriophages .

The pH optimum is 6.5–7.5, the temperature range is 10–35 ° C, the temperature optimum is 25 ° C.

Geochemical significance

The precipitation of oxide or hydroxide compounds of trivalent iron causes them to accumulate in sedimentary form as ocher , from which oxidic iron ore can be formed through solidification and dehydration . The precipitation of compounds of tetravalent manganese can also be of geochemical importance.

Systematics

The genus Leptothrix consists of the following species (as of 2014). Special features are also given.

See also

literature

  • Alberto Guielmo Roth: Catalecta botanica quibus plantae novae et minus cognitae discribuntur atque illustrantur . Fasciculus primus (part 1). Bibliopolio IG Mülleriano (Verlag IG Müller) Lipsiae (Leipzig) 1797, pp. 165-166. (Early description under the name Conferua ochracea ).
  • N. Cholodny: The iron bacteria - contributions to a monograph . In: R. Kolkwitz (Ed.): Pflanzenforschung , Issue 4. Gustav Fischer, Jena 1920.
  • EG Mulder: Genus Leptothrix Kützing 1843 . In: RE Buchanan, NE Gibbons (Ed.): Bergey's manual of determinative bacteriology . 8th edition. Williams & Wilkins, Baltimore 1974, ISBN 0-683-01117-0 , pp. 129-133.
  • John G. Holt, Noel R. Krieg, Peter HA Sneath, James T. Staley, Stanley T. Williams: Bergey's Manual of determinative bacteriology . 9th ed. Williams and Wilkins, Baltimore et al. O. 1994, ISBN 0-683-00603-7 , pp. 478-479, 482.
  • S. Spring, P. Kämper, W. Ludwig, K.-H. Schleifer : Polyphasic characterization of the genus Leptothrix. New descriptions of Leptothrix mobilis sp. nov. and Leptothrix discophora sp. nov. nom. rev. and emendet description of Leptothrix cholodnii emend. In: Systematic and Applied Microbiology . Vol. 19, 1996, pp. 634-643.
  • Stefan Spring: The genera Leptothrix and Sphaerotilus . In: Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt (eds.): The Prokaryotes . 3rd edition, Vol. 5. Springer, New York et al. O. 2006, ISBN 978-0-387-25495-1 , pp. 758-777.
  • George M. Garrity, Julia A. Bell, Timothy G. Lilburn: Taxonomic Outline of the Prokaryotes. Bergey's Manual of Systematic Bacteriology . Second Edition, Release 5.0. Springer-Verlag, New York, 2004. doi : 10.1007 / bergeysoutline200310 (currently unavailable) PDF .

Web links

Commons : Leptothrix  - collection of images, videos and audio files

Individual evidence

  1. ↑ D. Emerson, WC Ghiorse: Isolation, cultural maintenance, and taxonomy of a sheath-forming strain of Leptothrix discophora and characterization of manganese-oxidizing activity associated with the sheath . In: Applied and Environmental Microbiology . Vol. 58, 1992, pp. 4001-4010.
  2. ^ Jean Euzéby, Aidan C. Parte: Genus Leptothrix. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved August 8, 2014 .
  3. ↑ Michael J. Carlile, A. William L. Dudeney: The discs of Leptothrix discophora: lost for 89 vears? . In: Microbiology . Vol. 147, 2001, pp. 1393-1394.