Abstract
THE study of selective feeding2-5 of soil protozoa, especially amœbæ on a large number of bacterial strains, led to the development of an improved method6 of counting soil Protozoa. In the past, dilution methods7 of estimating Protozoa numbers have suffered, first from having too few replicates, and secondly from the use of unspecified bacterial food. These two difficulties have been met in the method described, the first by making a number of separate cultures enclosed by glass rings in each petri dish, and the second by using, as food supply, pure cultures of bacteria known to be edible to Protozoa. These food bacteria have in the past6 been spread on the surface of washed agar made up with 0.5 percent sodium chloride. It has been found, however, that silica jelly may be more advantageously used for two main reasons. First, it further reduces the growth of organisms coming in with the inoculum ; and secondly, it has another advantage over agar because it does not allow the growth of agar-liquefying organisms which may be abundantly present in certain substrates.
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SINGH, B. Silica Jelly as a Substrate for Counting Holozoic Protozoa. Nature 157, 302 (1946). https://doi.org/10.1038/157302b0
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DOI: https://doi.org/10.1038/157302b0
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