232 AGEICULTURAL AND INDUSTRIAL BACTEEIOLOGY 



Types of Organisms 



A comparatively small number of species of bacteria are 

 known which can attack pure protein in the absence of other 

 nutrients. A much larger proportion are able to decompose 

 proteoses, peptones and amino acids. 



The microorganisms responsible for bringing about 

 decomposition of protein may be grouped under the two 

 headings, anaerobic and aerobic. The former produce most 

 of the malodorous compounds ordinarily associated with 

 putrefaction. The latter are responsible for decomposition 

 in which such compounds are oxidized, that is, they bring 

 about the change ordinarily termed decay. 



The Anaerobic, Putrefactive Bacteria. — Certain mem- 

 bers of this group of microorganisms are capable of causing 

 disease. Such are the forms developing in blackleg and 

 malignant edema in animals, and the gaseous gangrene in 

 man. The saprophytic bacteria belonging to the group are 

 comparatively numerous. The most important species is 

 Clostridium putrificum. This organism is abundant in 

 nature in the soil. Together with several closely related 

 species it probably is the most common cause of putrefaction 

 of meat and similar proteins. The organism itself is a 

 slender rod, single or in chains. Its spores are developed in 

 the ends of the rods, causing them to be swollen and assum- 

 ing the shape of drumsticks. Microscopically the organism 

 has much the same appearance as Clostridium tetani, the 

 cause of tetanus. It grows readily in ordinary culture 

 media. It is capable of developing in a mixture of egg 

 white and water into which has been inoculated a little soil, 

 cheese or fecal material. When growing under these condi- 

 tions an intense putrefactive odor develops, probably due 

 largely to the formation of hydrogen sulphide and possibly 

 of methyl mercaptan (CH3SH). Butyric acid and am- 

 monia are also formed. This is one of the few bacteria 



