BACTERIA IN THE INDUSTRIES. 99 



tlierium and B. subtilis. According to some authorities it is especially con- 

 cerned in assimilating free nitrogen for gramineous plants. If it is true it 

 may prove of great value to grain grovi^ers. 



The commercial alinit is a dry pulverulent substance of a yellowish- 

 gray color, with about lo per cent, moisture and 2.5 per cent, nitrogen. It 

 is evidently prepared by mixing spore-bearing pure cultures of the bacillus 

 of Caron, with a base of starch and albumen. It is used to inoculate soil 

 either by spreading it broadcast or by sowing or otherwise planting it with 





Fig. 50. Fig. 51. 



Fig. 50. — Involution forms of R. mutabile as they occur in artificial culture (beef 

 broth). R. mutabile can be cultured quite readily upon a great variety of culture media, 

 showing marked adaptibility to variations in food supply and in environment. 



Fig. 51. — Azotobacter agilis deeply stained. This organism is actively motile as 

 indicated by the pressure of numerous cilia. The closely related species A . chroococcum 

 is less actively motile. Both possess the power of free nitrogen assimilation to a high 

 degree, especially - when cultured in a nitrogen-free medium. The organisms are large 

 (3 to 6 /i in diameter) in the comparative sense. Clostridium pastorianum is also an active 

 free nitrogen assimilator, but differs from the Azotobacters in that it forms spores, a prop- 

 erty which may render it highly valuable in economic agriculture as cultures in the sporu- 

 lating stage can be kept for a long time while the cultures of non-sporulating bacteria soon 

 die off or lose their potency. 



the seed. It is not a nodule or root tubercle-forming organism, and does 

 not enter into intimate symbiotic or biologic relationship with plants. Its 

 work is simply that of binding free nitrogen, forming nitrogenous compounds 

 which enrich the soil, thus increasing the yield of any crop benefited by such 

 compounds. 



It is known that there are soil bacteria which are more especially active 

 with certain plants or groups of related plants, and this peculiarity has 

 suggested the possibility of isolating them, artificially increasing their potency 

 and using them commercially for fertilizing purposes. It is also true that 

 not all soil bacteria are beneficent. Under certain conditions, pathogenic 

 and otherwise, harmful microbes are present in great numbers and become 



