RECOMBINANT AND WILD-TYPE PSEUDOMONAS-AUREOFACIENS STRAINS INTRODUCEDINTO SOIL MICROCOSMS - EFFECT ON DECOMPOSITION OF CELLULOSE AND STRAW

The effect of a genetically engineered Pseudomonas aureofaciens (Ps373 2RNL11) strain (GEM) and the parental wild-type (Ps3732RN) on decompos ition of cellulose paper, straw and calico cloth was assessed after 18 weeks incubation in laboratory soil microcosms. Effect(s) of inoculum density (10(3), 10(5), and 10(8) cells/g dry soil) and single versus multiple bacterial inoculations were also investigated. Cellulose pape r was completely decomposed after 18 weeks in all treatments. There we re no significant differences (95% level), between treatments, in perc entage decomposition of either straw or calico cloth. Recovery of the GEM at 18 weeks, using viable plating, was limited to treatments origi nally receiving 10(8) cells/g dry soil. Log 1.8 CFU/g dry soil were re covered from the single dose treatment while log 4.2 CFU/g dry soil we re recovered from the multiple dose treatment. Biolog metabolic tests were used to determine if the GEM or parental wildtype 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 su ggested the possibility of viable but nonculturable cells and/or persi stence of chromosomal DNA.