Toxothrix trichogenes
Tory Atwood
The year was 1924.  The location, a basin next to the river Dnjepr near Kiev, Russia.  A scientist by the name of Cholodny observed a bacterium that produced twisted bundles of filaments containing oxidized iron.  Originally named Leptothrix trichogenes, this bacteria had rigid, brittle, iron-encrusted bundles of filaments.  About fifty years later it was noted these bacteria had a U-shaped trichome that glided along with its rounded part forward.  This trichome was observed by Krul, et al in a partially immersed, phase-contrast microscope.  It was noted the movement of the U-shaped trichome consisted of symmetrical rotation of both ends. Under lab observation however, these trichomes lysed explosively.  This lysing could explain the lack of observation of trichomes in the first lab.  Three years after the discovery of the trichomes, the proper name of Toxothrix trichogenes was employed.

This organism is very uncommon in nature, however, when observed it is found in fairly cold iron springs under conditions of reduced oxygen tension and acidic pH.  These bacteria are considered psychrotrophs because the highest temperature at which it has ever been reported is 15.5 C.  The required ferric iron concentrations are low at approximately 1-2.7 mg/L Fe 2+.  T. trichogenes is often accompanied by other bacteria such as: Gallionella ferruginea, Leptothrix spp., Siderocapsa spp., etc.  Usually the best conditions for the growth of T. trichogenes has a high concentration of organic matter and
microaerophilic conditions.

This bacteria can be found in nature sometimes, but it is almost impossible to obtain in pure culture.  In fact, to this date a pure culture has not been obtained.  Though no pure culture exists, any T. trichogenes obtained in nature can be stored in the lab for several months under ideal conditions.  These conditions include organic sediment, cold temperatures (5oC), and darkness.

As stated previously, the trichomes tend to lyse under microscopic examination.  It is proven the lysis is not caused by temperature, light intensity, nor lack of oxygen. The reason for the lysis is believed to be caused by the pressure of the cover slip.  Another problem is when the organism is streaked for the same reason. 

When working with T. trichogenes the medium should have a pH of 5.5-6.5, a constant iron supply of no more than 1-2 mg/L Fe 2+, and an oxygen concentration of about 1mg/L.  Incubation should take place in the dark at 5-10 C.

Though not named yet it is thought possibly more than one Toxothrix species exists.  This is thought because sometimes
fragmentation of the trichomes into short rods is common in some habitats, but not others.  When fragmented, each cell contains two polyphosphate granules (volutin), one at each end of the cell.

The fact that new observations are being made everyday gives hope that a new Toxothrix species may be found.
 

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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