USE OF THE MICROSCOPE IN STUDYING THE ACTIVITIES OF BACTERIA IN SOIL

Abstract

The microscopic method for studying bacteria in soil, first proposed in 1917, was intended as a method of checking up other procedures for counting bacteria and as a means of determining the morphological types present. Recently Winogradski has employed the method for observing the kinds of organisms stimulated by addition of various ingredients to soil. It has been recognized for some time that the behavior of organisms in soil and in laboratory media may be very different. Without question it is more important to know their behavior in soil, but the difficulty of studying their physiology in soil has kept investigators from making much progress here. Following the line of investigation suggested by Winogradski''s work, the writer has found that the microscopic method promises to be fully as important for studying the food requirements of bacteria in soil. A soil may be selected in which microorganisms under investigation do not grow. Various nutrient materials may be added to different lots of soil and each lot sterilized in test tubes. Then the various tubes may be inoculated with the organism to be studied, and its ability to grow may be learned by microscopic examination. By using this method, interesting information has already been obtained about one previously unknown but very abundant organism in soil, and further data are being collected about others.