Schubert R H
Zentralbl Bakteriol Orig B. 1975 Mar;160(2):155-62.
Due to their differentiated nutritional requirements the species of the genus Bacillus found in large number in the waste matter and the upper layers of the soil and consequently in the surface water cannot multiply in biotopes of low nutritive content. However, they are spread to these areas as spores and are of extraordinary tenacity if not eliminated. Consequently, in the ground water and within the range of its utilization they represent an indicator of the degree of purification or contamination of the water with waste products or surface impurities; their number does not depend on the phase of self-purification (as e.g. the number of colonies) in the sense of the degradation of remaining substances still utilizable by pseudomonads. The concentration of spores of the Bacillus species in the surface water ranges from 1000-10000 per 50 ml of water. In undisturbed ground water 0-5 per 50 ml are found; in filtered ground water from near the banks and in such water that has been exposed to surface contamination 1000 per 50 ml have been found or even more; in the direction of infiltration - proportionate to the purification effect in the ground - decreasing numbers of spores of the Bacillus species are detectable. In "areas of subsequent germination" of the water supply and water utilization no multiplication of spores of the Bacillus species has been observed - provided no additional contamination occurs.
