26 MYCOLOGY 



experimenting with the j)hosphoie.sceiit bacteria, for these organisms 

 require in their culture media from 2 to 3 per cent, of sodium chloride, 

 besides the usual salts and peptone, the medium should contain some 

 other source of carbon, such as sugar, glycerine, etc. The number of 

 known photogenic bacteria is considerable. Migula names twenty- 

 five species and Molisch twenty-six. A few need only be mentioned 

 here, viz.: Bacterium phosphorescens Fischer; Bacillus photogenus 

 Molisch; B. luminescens Molisch; Microspira glutinosa (Fischer) 

 Migula; M. luminosa (Beijerinck) Migula; Pseudomonas javanica 

 (Eijkmann) Migula. The results of numerous experiments are that 

 the production of light by bacteria is an exclusively aerobic phenome- 

 non, for in the absence of oxygen, they are non-luminous. The light 

 is sometimes strong enough that jars containing luminous bacteria can 

 be photographed by the light emitted by the organisms within the jar. 



Chromo genie Bacteria. — Most bacteria are colorless and even in such 

 forms in which color is associated with their growth on culture media, 

 the organisms are colorless. The bacillus which causes the "bleeding 

 host," Bacillus prodigiosus, is colorless with the pigment in the form of 

 granules scattered about between the bacterial cells. In other cases, 

 the pigments and fluorescent substances are diffused in the culture 

 medium outside the living cells. Hence, we may call such bacteria as 

 chromoparous. The chromophorous species are those in which the 

 protoplasm is actually colored. Such are some sulphur bacteria 

 Chromatium and Thiocystis, and finally, there are some forms as Bacillus 

 violaceus in which pigment is lodged in the cell wall, when we may call 

 them parachromatophorous. Practically all of the colors of the spectrum 

 are represented in the color productions of bacteria: violet {Bacillus 

 violaceus), indigo (B. janthinus), blue {B. pyocyaneus), green [B. 

 fluorescens), yellow {Sarcina lutea), orange {Sarcina aurantiaca) and red 

 {B. prodigiosus). The erythrobacteria, or colored sulphur bacteria, 

 are unique in the power of assimilating carbon dioxide in the presence 

 of sunUght by the activity of bacteriopurpurin (a red coloring matter^ 

 which behaves like the chlorophyll of green plants. 



Thermogenic Bacteria. — Such substances as hay, silage, manure anc 

 cotton waste frequently become heated, the temperature inside the 

 mass being raised to 60° or 7o°C. This spontaneous heating is due tt 

 the respiratory activity of the thermogenic bacteria of Cohn (aerobic) 

 which set up fermentation and putrefaction. The horticulturist use.- 



