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CONTIUBUTIONS TO OUR KNOWLEDGE OF SOIL- 



FEUTTLTTY. 



iii. — Bactkkial Slimes in Soil. 



By R. Greig-Smith, D.Sc, Maclkay Bactekiologist to the 



Society. 



Many of the bacterial colonies tliat develop upon plates of 

 saccharine nutrient media after sowing with dilute suspensions of 

 soil, contain slime or gum. As the bacteria that go to form the 

 colony are actively producing slime at the moment of their isola- 

 tion, and continue to do so, it is reasonable to expect that they 

 were capable of producing this (-haracteristic product while they 

 were in the soil. It is also reasonable to suppose that they had 

 been producing slime in the soil at no very distant date, or else 

 the slime-forming facult}^ would have been in abeyance. With 

 this assumption, we should expect to find bacterial slimes in soils 

 if the condititms were such as to prevent their decomposition by 

 other bacteria. 



The slimy colonies are various, and a simple inspection is 

 sufficient to show that the bacteria vary morphologically accord- 

 ing to the colony, and that the nature of the slimes is different. 

 Some are thin, others viscous, others gelatinous. From a con- 

 siderable experience with slime-forming bacteria, isolated from 

 the tissues of plants and other material, I have no hesitation in 

 saying that the majority of slime-forming bacteria produce 

 galactan as their typical carbohydrate. With this knowledge to 

 work upon, it should be easy to test the matter and, if galactans 

 are found in soil, I submit that we are justified in assuming that 

 they have been produced there by the action of slime-forming 

 bacteria. 



In soils, we expect to find many varieties of carbohych-ates 

 resulting from the introduction or growth and subsecjucnt decay 



