Recombinant and wild-type Pseudomonas aureofaciens strains introduced into soil microcosms: effect on decomposition of cellulose and straw


  • This research was carried out in the laboratories of J.T. Trevors and H. Lee who are conducting research in microbiology with an emphasis on biodegradation of contaminants in soil and the use of molecular techniques in microbialecology. This paper is part of the doctoral research of L. England who is studying survival, persistence and non target effects of a genetically engineend micro-organism in soil.

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The effect of a genetically engineered Pseudomonas aureofaciens (Ps3732RNL11) strain (GEM) and the parental wild-type (Ps3732RN) on decomposition of cellulose paper, straw and calico cloth was assessed after 18 weeks incubation in laboratory soil microcosms. Effect(s) of inoculum density (103, 105, and 108 cells/ g dry soil) and single versus multiple bacterial inoculations were also investigated. Cellulose paper was completely decomposed after 18 weeks in all treatments. There were no significant differences (95% level), between treatments, in percentage decomposition of either straw or calico cloth. Recovery of the GEM at 18 weeks, using viable plating, was limited to treatments originally receiving 108 cells/g dry soil. Log 1.8 CFU/g dry soil were recovered from the single dose treatment while log 4.2 CFU/g dry soil were recovered from the multiple dose treatment Biolog metabolic tests were used to determine if the GEM or parental wild-type had any effect on overall carbon utilization in soil. Results suggested they did not. Detection of the recombinant lacZY gene sequence in soil using PCR suggested the possibility of viable but nonculturable cells and/or persistence of chromosomal DNA.