BACTERIA AS CHEMICAL AGENTS 



In this book we shall concern ourselves with bacteria only 

 as, although it is by no means certain that these are the most 

 active of the micro-organisms, they have been studied more 

 intensively up to the present than the other types. 



Bacteria have such a wide distribution that there are few 

 places on or near the surface of the earth, in the waters of 

 the earth, or in the air near the earth, which are free from them. 

 They are found in hot mineral springs, in Arctic snows, in 

 stagnant salt lakes, in oil-saturated soil around oil-wells, in 

 the acid effluents from gas-works, etc. The only places free 

 from bacteria are those in which a sterilising influence is at work ; 

 where heat, sunlight, or caustic chemicals render life impossible, 

 or in the interior tissues of healthy plants and animals. 



Bacterial multiplication takes place under most diverse 

 conditions and bacterial multiplication involves the formation 

 of cell-substance or protoplasm which, in turn, involves the 

 synthesis of all the complicated concomitants of free-living 

 existence such as proteins, amino-acids, carbohydrates, 

 lipoids, nucleic acids, growth factors, prosthetic groups of 

 enzymes, etc. Many of these substances can be synthesised in 

 the laboratory only with extreme difficulty, if at all. Not only 

 is there the synthesis of complex molecules to be accomplished 

 but in many cases these syntheses are further complicated by 

 considerations of positional isomerism which give rise to the 

 formation of several substances of the same empirical formula, 

 only one of which is biologically effective. To take a simple 

 example, we have the amino-acid R.CHNHg.COOH which, 

 as it contains an asymmetric carbon atom, exists in two 

 isomeric forms, one the structural mirror-image of the other. 



