PRODUCTS OF THE GROWTH OF BACTERIA. I17 



CHAPTER II. 

 PRODUCTS OF THE GROWTH OF BACTERIA. 



Phosphorescence. — Bacteria "whose cultures exhibit phos- 

 phorescence have been found in the ocean and in fish. 



Chromogenic Bacteria.— Many bacterial growths display 

 brilliant coloring. The different species of sarcinae are re- 

 markable for forming highly-colored growths; some of them 

 are rose-red, some orange-yellow, some lemon-yellow, and so on. 

 The bacillus prodigiosus presents a brilliant red growth whose 

 rapid development is said to have formed the basis for the so- 

 called "Miracle of the Bleeding Host" (see page 5). The 

 bacillus pyocyaneus in culture gives a brilliant green fluores- 

 cence and is responsible for the color of blue or green pus. 

 Bacilli which exhibit a green fluorescence in cultures are com- 

 mon in water. In cultures on potato or agar the colors of 

 the chromogenic forms are usually well shown. The pigment 

 formed by the chromogenic bacteria is not produced in the cells 

 themselves. These are colorless. The color is due to sub- 

 stances excreted by the cells, or formed from material in the 

 culture- media. 



Ferments or Enzymes.* — Many bacteria form ferments 

 which have the power of dissolving proteid substances in a 

 manner similar to trypsin. The " liquefaction of gelatin is a 

 familiar example of this process. The property of liquefying 

 gelatin, or the failure to do so, is used in classifying bacteria 

 and in determining the nature of unknown species. 



Some bacteria, as the bacillus coli communis, form ferments 



* Consult Buxton. Mycotic Enzymes. American Medicine. July 25, 1903. 



