Christian G. Daughton

Accelerated parathion degradation in soil by inoculation with parathion-utilizing bacteria.

The use of microorganisms for the decontamination of pollutants in the environment is only a recently acknowledged feasibility, even though sewage and certain industrial liquid wastes are routinely treated biologically. Nearly all of the research has been directed toward the use of microbial preparations for the cleanup of oil spills (BERNER et al., 1975; MIGET, 1973; STEWART, 1975); several oil-degrading microbial preparations are commercially available (ANONYMOUS, 1970; ATLAS and BARTHA, 1973). Potential problems involved with the use of microbial inocula in the environment have been discussed in reference to oil cleanup (COBERT et al., 1973; ZOBELL, 1973). Only in the past decade have investigators shown that soil undesirably contaminated with a pesticide could possibly be decontaminated by inoculation with specifically adapted microorganisms. This idea perhaps was first embodied in the experiments of AUDUS (1951), who inadvertantly showed that bacteria, acclimated to utilize the herbicide 2,4-D, could acelerate its disappearance from soil when applied as an inoculum. Probably not for another 15 years did anyone attempt to use acclimated microorganisms for the purposeful detoxication of pesticides in soil. MACRAE and ALEXANDER (1965) attempted to protect alfalfa seeds from the herbicide 4-(2,4-DB) by inoculation with a heavy suspension of 4-(2,4-DB)-utilizing Fiavobacterium sp. prior to planting. ANDERSON et al. (1970) inoculated soils containing 1 ppm DDT with spore suspensions of a DDT-degrading fungus. BOYCE THOMPSON INSTITUTE researchers (1971) inoculated soil containing the herbicide Bromacil with Penicillium paraherquei which could degrade 20 ppm Bromacil in liquid culture. LEHTOM~KI and NIEMELA (1975) added large inocula of axenic oil-degrading bacterial cultures to oil-contaminated soils. All of these studies were under laboratory conditions, and results were negative for nonsterile soils inoculated with the various microorganisms. On the other hand, there have been positive results from the inoculation of non-sterile laboratory soil. KEARNEY et al. (1969) showed accelerated DDT disappearance from flooded soils inoculated with DDT-acclimated Enterobacter aero~enes. CLARK AND WRIGHT (1970) showed that the phytotoxicity of isopropyl N-phenylcarbamate (IPC)-fortified soils was decreased by inoculation with IPC-utilizing Arthrobacter sp. SETHUNATHAN (1973) reported that 26.5 ppm parathion in flooded soils could be hydrolyzed at a rate