IRON BACTERIA 557 



segments are shorter. It is motile, flagellated, and sporing, and 

 stains by Gram's method. 



Some confusion exists respecting the thread forms of the 

 mouth. 1 



Cladothrix dichotoma and Iron Bacteria 



An organism not unfrequently met with in natural waters. It 

 forms long threads, straight, or sometimes slightly undulating, 

 or even spiral and apparently branched, though the branching 

 is not dichotomous. It can be cultivated on the ordinary labora- 

 tory media at room temperature, forming on agar a brownish, 

 wrinkled, tough, membranous layer, very adherent, and staining 

 the medium beneath it a pale brown, not unlike the Actinomyces 

 in these respects. It is non-pathogenic. 



Certain organisms of this type have been termed " iron bacteria " 

 owing to their capacity for abstracting iron from the water in 

 which they live, collecting it in the form of ferric hydroxide and 

 depositing it on their cell-membranes (Leptothrix, Gallionella, 

 Grenothrix, etc.). They may form rust-coloured streamers in 

 water, which may be so numerous as to colour the water and 

 render it offensive, as at Cheltenham in 1896. They have also 

 been supposed to produce the nodular incrustations on old iron 

 pipes. 2 



1 See Goadby, Mycology of the Mouth. 



2 See Iron Bacteria, D. Ellis (Methuen & Co., 1919). 



