176 Microbes and You 



applications, such as the use of heating manure in hot beds and 

 cold frames and preventing the freezing of newly poured concrete 

 during the winter months. 



The production of vinegar by the more rapid methods which 

 employ so-called generators, can result in the formation of suf- 

 ficient biological heat to destroy the vinegar organisms unless cor- 

 rective measures can be taken to control the high temperature 

 produced by the microbial action. Tobacco subjected to the 

 "sweating process" is piled in stacks and allowed to heat to tem- 

 peratures of 55-60° C. before the piles are dismantled and the 

 leaves are hung up to dry. The heat generated in loosely packed 

 silage can be sufficient to interfere with proper fermentation. 



Only when heat production by microorganisms is rapid and 

 cumulative is the term thermogenesis usually applied. While it is 

 true that the amount of heat produced by a single bacterial cell 

 is not very great, the combined effect of billions of organisms is 

 considerable. It has even been suggested that in areas where 

 grain is abundant, and cheap in price, homes might be partially 

 heated by microbial thermogenesis in this substrate packed between 

 the walls of the house. 



PHOTOGENESIS (BIOLUMINESCENCE) 



A curious group of bacteria, found most abundantly in sea 

 water, are endowed with the power of emitting light during their 

 metabolism. Some of these light-producing bacteria grow as 

 parasites or as opportunists on various types of marine life, but no 

 pathogenicity for laboratory animals or for humans has been 

 demonstrated. 



If your travels ever take you into a fish market after dark, 

 peering into the barrel where the fish heads are discarded may 

 reveal an eerie glow, particularly if air is blown over the surface 

 of the fish. Should you by chance be carrying a tank of oxygen 

 on your back at the time, a stream of this gas directed into the 

 barrel will activate any bioluminescent bacteria that are present. 

 Caution: Don't smoke during this experiment! 



Organisms which are phosphorescent are said to be photogenic; 



