dilution allowing only living spores to pass the subsequent test-tubes 

 from which water is inoculated onto NIPA. 



The Number Specific Bacteria 



Consideration of the field of medical microbiology is beyond the scope 

 of this paper. It should only be indicated that highly dangerous microor- 

 ganisms causing infectious diseases may be isolated using special media 

 and methods of enrichment. Isolation of such bacteria indicates a great 

 danger of such water for the health of people. Such water is quarantined, 

 and specific measures are to taken to protect the health of the public. 

 Fortunately such microorganisms are rarely present in water. Usually they 

 enter the water as a result of illness or from carriers. Some species of 

 bacteria may be indicators of pollution of the water by a certain type of 

 organic substances. For example, species of the filamentous bacteria of 

 the genus Cladoth/iix. are indicative of the presence of nitrogen-free or- 

 ganic compounds in water, and the presence of species of the genus 

 Spha&iotlliu indicates to pollution of the water by complex organic com- 

 pounds of nitrogen (Rasumov, 1961). 



Coliform Titer 



The presence of coliform bacilli in water is indicative of a fresh 

 pollution with feces. In the water, high concentrations of these bacilli, 

 which are normally inhabitants of the human intestine, indicate pollution, 

 and the possible presence of pathohenic bacteria. Though certain strains 

 of coliform bacteria may persist for long periods of time and even multiply 

 in water, fresh fecal pollution is detected by those strains which only re- 

 cently entered the water. These are discerned by a characteristic colora- 

 tion of the colonies. 



The number of these bacteria in water is determined by inoculation 

 with the highly specific Endo medium. The colonies can be grown either on 

 this medium directly in Petri dishes, or on membrane filters. In the 

 latter case, the water is passed through the filter, and it in turn, is 

 placed on Endo agar. Gold-colored colonies with a characteristic metallic 

 lustre are counted. The coliform titer is taken as the quantity of water 

 per one coliform-bacillus. 



Separate Physiological Groups or Separate Characteristic Bacteria 



The presence of a certain class of mineral or organic compounds in 

 water bodies may be established by the presence or increased content of 

 specific groups of bacteria. In many cases, it is easier to detect the 

 presence of such bacteria than it is to establish the presence of certain 

 chemical substances. It is generally accepted that it is possible to iso- 

 late separate microorganisms responsible for specific processes. An indi- 

 cation of the presence of that process is demonstrated by detection of an 

 increased content of a certain species or genera of bacteria. 



Presence of Liquid Hydrocarbons (Oil Pollution) In Water- 

 Pollution of water or bottom sediments can be estimated by an increased 

 content of hydrocarbon oxidizing bacteria. For this process the samples 



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