CLASSIFICATION 5 



Crenothrix. Unbranched chains, dividing in three planes, forming rounded 

 daughter cells. 



Phragmidiothrix. Cells first unbranched, with very delicate sheath, 

 dividing in three planes and sometimes branching later. 



Thiothrix. Unbranched, non-motile threads, containing sulphur granules, 



dividing in one plane only. 



Beggiatoaceae. Cells without capsules, joined in unbranched threads; 

 provided with an undulating membrane. 



Beggiatoa. Cells with the characteristics of the family, containing sulphur 

 granules. 



Orla Jensen's classification is based upon the nutritive characteristics. In 

 this the bacteria are grouped according as they are: (i) autotrophic, i.e., able 

 to form protein and carbohydrates from inorganic carbon and nitrogen; (2) 

 semi-autotrophic, i.e., require organic carbon compounds, but able to form 

 protein from inorganic nitrogen; or (3) heterotrophic, i.e., requiring for nourish- 

 ment organic compounds of both carbon and nitrogen. 



There are excellent reasons for accepting the suggestion of Victor Vaughan, 

 who believes it expedient to consider bacteria as such, and to classify them as a 

 separate group of living organisms, and not as a branch of either the vegetable 

 or animal kingdoms. 



Some bacteria are motile, and progress either by an undulatory movement, a 

 screw-like rotary movement, or as darts; the latter possess extremely fine, long 

 thread-like processes, called flagella; these are believed to be the organs of 

 locomotion. 



"Structurally, bacteria consist of protoplasm, which at the periphery is 

 condensed to form a layer resembling a cell wall. While a nucleus has not been 

 demonstrated, it is probable that practically the whole cell is composed of 

 nuclear matter, there being but a thin peripheral layer of perinuclear proto- 

 plasm" (Coplin). 



Some bacteria are surrounded by a capsule. 



The chemical composition of bacteria varies for different organisms and is 

 somewhat dependent upon the nutritive substances upon which they live. 

 From 75 to 85 per cent, is water, 5 to 10 per cent, protein, 5 to 25 per cent, fats 

 and i to 2 per cent, ash; chlorophyl is not found. 



When environment becomes adverse to further development, some bacteria 

 can transform into spores. Briefly stated, the first sign of endospore formation 

 is a granular appearance of the cell protoplasm; these granules increase in size, 

 collect in one part of the cell and coalesce, forming a round, highly refractile 

 body, larger in diameter than the bacillus and hence causing a bulging of the cell 

 wall. The cell protoplasm gradually, and in increasing amount, concentrates 

 in the endospore; eventually the bacillus has disappeared and in its place remains 

 only the endospore, globular, highly refractile, containing very little water, very 

 much more resistant to germicides than the bacillus from which it sprung. 

 Spore formation is not a method of reproduction or propagation. It is a device 

 to resist destruction, a process of involution. 



