A Simple Device for Collecting Soil Cores for Microbiological Studies

Abstract

Soil samples have been collected for study in this laboratory by simply scooping up surface soil with a sterile glass culture tube, or for samples of deeper soil layers, digging a trench and pushing the mouth of a tube into a freshly exposed surface of the wall of the trench. This method presents a number of problems foremost of which are: tubes are easily broken in gravelly soil; some soil always sticks to the mouth of the tube, presenting a contamination problem in the laboratory; and the cotton plug often becomes covered with soil which dries to produce a dust aerosol when the tube is opened. As many of the samples processed are suspected of containing fungi pathogenic to man, the importance of the last two disadvantages of this method is readily apparent. A rather simple solution to all three problems was accomplished by modification of Tomac polypropylene plastic disposable syringes. We use 20-cc syringes because relatively large samples are required for our studies; however, smaller syringes are suitable where smaller samples are desired. Because they are calibrated volumetrically, the size of a sample can be readily determined. The syringes are modified in the following manner: the plunger is removed, then the tip is cut from the syringe barrel at the 0 graduation by means of a hacksaw or a similar small-toothed saw. If more than a few such samplers are to be made, a simple miter box-like device can be made to hold the saw and position the syringe. The end is then beveled as shown in FIG. 1A, using either coarse sandpaper or a suitable file, and then smoothed with a knife or scalpel. The rubber tip is taken off the plunger and pushed down the syringe barrel to about the 2-cc mark. The barrel with its plunger tip are then placed in a glassine syringe bag or other suitable wrapper and sterilized by autoclaving. The plunger handle is made of a different type of plastic which will not withstand autoclaving; however, since it is used only to push the core from the filled sampler, it does not need to be sterilized. Surface samples are taken by pushing the sampler into the soil with either a twisting or rocking motion until it is filled to the desired level. When deeper samples are to be collected, a trench is dug and lateral cores 191