INTRODUCTION OF ANAEROBIC DECHLORINATING BACTERIA INTO SOIL SLURRY MICROCOSMS AND NESTED-PCR MONITORING

Desulfomonile tiedjei and Desulfitobacterium dehalogenans were chosen as model bacteria to demonstrate the introduction of an anaerobic micr obia reductive dechlorination activity into nonsterile soil slurry mic rocosms by inoculation. De novo 3-chlorobenzoate dechlorination activi ty was established with the bacterium D. tiedjei in microcosms normall y devoid of this dechlorination capacity. The addition of D. tiedjei t o microcosms supplemented with 20 mM pyruvate as the cosubstrate resul ted in total biotransformation of 1.5 mM 3-chlorobenzoate within 7 day s. The introduction of the bacterium Desulfitobacterium dehalogenans i nto nonsterile microcosms resulted in a shortening of the period requi red for dechlorination activity to be established. In microcosms inocu lated with Desulfitobacterium dehalogenans, total degradation of 6 mM 3-chloro-4-hydroxy-phenoxyacetic acid (3-Cl-4-OHPA) was observed after 4 days in contrast to the result in noninoculated microcosms, where t he total degradation of 3-Cl-4-OHPA by indigenous microorganisms was o bserved after 11 days. Both externally introduced bacterial strains we re detected in soil slurry microcosms by a nested-PCR methodology.