Effects of certain full and partial sterilization treatments on leaf litter

Abstract

Experiments are described which tested the effects of X-rays, gamma-irradiation, autoclaving, and propylene oxide on the organisms and chemical composition of hazel and oak leaf litter. X-ray treatment at 0.02 Mrad produced no major changes in the composition of the microbial populations, nor significant changes in the chemical composition of the litters. However, this treatment has been used to kill animals in litter, and it is a suggested treatment of litter if micro-organisms are to be studied in the absence of animals, or if a different population of animals is to be introduced. Autoclaving, gamma-irradiation, and propylene oxide, were effective as total sterilizing treatments: a Bacillus species was the only survivor detected. The results confirm that autoclaving is the most drastic of these treatments, and it appears to reduce the content of soluble tannins in the litter. Propylene oxide has certain disadvantages, which are discussed. Gamma-irradiation is at least as effective as autoclaving in killing organisms, and may he more so, as the Bacillus species appeared to be damaged more by irradiation than by the other treatments. Gamma-irradiation appears to leave at least some enzyme systems functioning, but storage of the treated material before use allows free enzyme activity to decline. The effect of storage time on free enzyme systems needs further study.