BACTERIA III 



All of these iron bacteria have the power of changing certain 

 soluble salts of iron into insoluble forms and thus precipitate them from 

 solution. Growing in the pipes of a city water supply their deposits 

 choke up the pipes and hence they are frequently referred to as "water 

 pests." As a result of researches in recent years these iron bacteria are 

 now regarded as important geological agents and to them is ascribed a 

 large share in the deposition of iron ores. 



Other thread bacteria of considerable importance are the acti- 

 nomycetacea. Some of them are common in the soil and recently 

 have been given special study. Others cause disease and a well known 

 form, Actinomyces boms Hartz, is the cause of lumpy jaw in cattle. 



The actinomycetes are mold-like organisms and often show true 



branching. They reproduce vegetatively or by means of conidia. 



They are without sulphur granules, not colored with bacteriopurpurin 



and the sheaths, if present, are not impregnated with iron. The struc- 



I ture of Actinomyces boms is shown in Fig. 165, p. 780, while the charac- 



| teristic radiating clubbed ends of the filaments, as these organisms grow 



in the tissues of cattle, are shown in Fig. 164, p. 779. 



THE SULPHUR BACTERIA. The sulphur bacteria are filamentous 

 forms which may reach a length of many microns. They are cylin- 

 drical or perhaps sometimes flat. They may be either attached or 

 actively motile. The movement when present is due not to flagella, 

 f but to an undulatory motion like that of the spirochaetes or Oscillaria 

 among the algae. As they move forward they rotate on their own axis 

 and swing their free ends. 



Spore formation is unknown in some forms where multiplication is 

 accomplished by the breaking up of the threads in short segments. 

 In the case of the sessile forms conidia are produced at the end of the 

 thread and are motile (Thiothrix nivea). The sulphur bacteria contain 

 at certain stages strongly refractile sulphur granules in their bodies. 



CLASSIFICATION* 



The classification of bacteria was early recognized by Mueller as a 

 matter of difficulty, since he says: "The difficulties that beset the in- 

 vestigation of these microscopic animals are complex; the sure and 

 definite determination (of species) requires so much time, so much of 

 acumen of eye and judgment, so much of perseverance and patience, 

 that there is hardly anything else so difficult." 



Prepared by W. D. Frost. 



