156 



OUTLINES OF BACTERIOLOGY 



Fig. 93. — Leptothrix ochracea. 



Leptothrix ochracea (Kiitzing) syn Chlamydotlirix ochracea 



(Migula). This is the commonest of the iron-bacteria, and is 

 found in every country in Europe. In nearly all the samples of iron- 

 water that have been examined, 

 — this species is the predominating 

 ^^^^^^__^^^^_^__^^^^ organism. It was discovered as 



early as 1843 by Kiitzing, who 

 placed it among the algae, but a 

 later investigation resulted in a transference to the thread-bacteria 

 (Chlamydobacteriaceae). The organism is cylindrical in shape, with 

 a fairly thick membrane, which is usually sharply outlined both on 

 the inside and. on the outside (Fig. 93). Although each individual 

 is not attached to any object, it is not un- 

 usual in a young growth of this organism 

 to iind a large colony attached as a whole 

 to the bed of a small brook. In such a 

 colony the individual members are con- 

 nected together to form an irregular net- 

 work, the whole swaying to and fro in the 

 water. Even in a network of this nature 

 the ends of the individual organisms are 

 free. Fig. 94 represents the mode of attach- 

 ment of the individual organisms with one 

 another. This appearance is seen only in 

 comparatively young growths in which the 

 deposition of iron has not as yet taken 

 place to a very large extent. After a while 

 the continuous deposition of iron on the surface of the organisms 

 makes the weight so heavy that the whole colony collapses, and 



henceforth each thread lies prostrate on 

 the bed of the stream. 



The length of a Leptothrix thread varies 

 considerably : the average is from 100 j«. 

 to 120 jx. The average width is •2-2-5 /i, 

 though owing to the deposition of iron on 

 the membrane it often appears to be much 

 more. The thickness of the wall also 

 varies considerably, being thin and delicate 

 in young individuals, and thicker and more sharply defined in the 

 older threads. 



Multiplication is effected either by a process of division or by the 



Fig. 94.— Leptothrix ochracea. 

 Diagrammatic representation 

 of colony of young threads 

 attached to bed of stream. 



Fro. 96.— To illustrate method of 

 diTision in Leptothrix ochracea. 



