ENUMERATION OF SOIL CILIATE ACTIVE FORMS AND CYSTS BY A DIRECT COUNT METHOD

A two-step direct count method may be used to determine the proportions of active and encysted ciliates in soils. Ten 5 cm deep samples are collected with a 1 cm diameter cork borer from a 4 m2 area. The samples are thoroughly mixed and a 0.6 g subsample weighed. Of this, 0.2 g is mixed with 3 ml sterile soil extract and examined drop by drop and active ciliates recorded. The remaining 0.4 g is mixed with 10 ml bacterized soil extract, and 0.04-ml aliquots added to the inner 60 wells of a 96-well microtiter plate. The outer wells are filled with distilled water, the plate covered, and incubated at 20-23-degrees-C for 6-7 days. Each well is examined for ciliates, and the numbers and species recorded. From these two counts, active forms, cysts, and total numbers, per gram are calculated.