Feb. 14, 1916 
Longevity of Soil Micro-organisms 
929 
Ficker (8) states that the temperature at which the organisms are 
cultivated and their ability to resist drying at different temperatures 
stand in a certain relation. Drying at a higher temperature does not 
always produce a more rapid effect and the drying at a lower temperature 
a more gradual effect. He concluded that cultivation at a temperature 
below the optimum produces an individual with the greatest resistance 
to desiccation. His results (7) with the drying of cholera vibrio cultures 
of different ages indicate that cultures 1 or 2 days old endure desiccation 
better than older cultures, but of these two the 48-hour culture is less 
sensitive to drying at 37 0 C. than is the 24-hour culture. The results of 
Kitasato and Berckholtz, quoted in the same article, show about the 
same resistance in cultures from 1 to 5 days old. Cultures older than 
these showed a marked decrease in resistance, due not only to the fact 
that there were fewer living organisms present in the same mass of an old 
culture, but these surviving organisms possessed in themselves less 
vitality than did the vibrios from younger cultures. Ficker (7) also 
demonstrated in the case of the cholera vibrio that a virulent strain was 
more resistant than an avirulent strain. Fickeris experiments (8) showed 
that transfers of old cholera vibrios from the surface of agar to distilled 
water resulted in a disturbance of the turgor of the cell which was so 
injurious as to make its death, when desiccated, occur much sooner than 
was the case when they were suspended in physiological salt solution 
and dried. With young cultures the reverse was true. Suspension in 
tap water or distilled water appeared to have the same effect, but desic¬ 
cation after suspension in physiological salt solution was quickly injurious. 
He explains this on the basis that since the drying process resulted in an 
increase of concentration of the salt solution, the cell was subjected to 
both plasmolysis and desiccation. The explanation is not complete, 
however, for a broth of the same salt content as the physiological salt 
solution was favorable to both young and old cultures. He found (8) the 
cholera vibrio to retain its vitality longer when dried from a suspension 
in milk or broth than in distilled water, tap water, physiological salt 
solution, serum, or saliva. Ficker (8) also showed that a greater lon¬ 
gevity resulted after drying on cover-glass films when the organisms were 
first cultivated on a solid medium and then suspended in ixish. broth or 
milk, than when they were grown in those liquids and then dried on 
cover-glass films prepared directly from the medium in which they 
developed. 
Peiser (17) showed that the thermal death point of lactic-acid bacteria 
when determined in milk is higher than when determined in bouillon. 
Numerous examples are cited of the long preservation of organisms in a 
dry state when surrounded by nitrogenous or albuminous material. 
Chester (4) says that Pseudomonas radicicola , when dried in thin films on 
glass, perishes very rapidly, but that it may live 11 to 16 days on cotton. 
Harding and Prucha (23) have shown that Bacterium campestris may 
