Dissemination of catabolic plasmids among desiccation-tolerant bacteria in soil microcosms.
The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trichloroethene and isopropylbenzene degradation pathways, was used as the inoculum, no transconjugant was isolated but the strain remained in the soil. This plasmid had a narrow host range. Pseudomonas putida strain C8S3 was used as the inoculum in a second approach. It bore a broad host range conjugative plasmid harboring a natural transposon, RP4::Tn4371, responsible for biphenyl and 4-chlorobiphenyl degradation pathways. The inoculating population slowly decreased from its original level (10(6) colony-forming units [CFU]/g of dry soil) to approx 3 x 10(2) CFU/g of dry soil after 3 wk. Transconjugant populations degrading biphenyl appeared in constant humidity soil (up to 2 x 10(3) CFU/g) and desiccating soil (up to 10(4) CFU/g). The feasibility of plasmid dissemination as a bioaugmentation technique was demonstrated in desiccating soils. The ecologic significance of desiccation in bioaugmentation was demonstrated: it upset the microbial ecology and the development of transconjugants.
Weekers
F
F
Walloon Center for Industrial Biology, University of Liege, Belgium. p.thonart@ulg.ac.be
Rodriguez
C
C
Jacques
P
P
Mergeay
M
M
Thonart
P
P
D001419:Bacteria / Q000235:genetics*; D018407:Bacterial Physiological Phenomena; D001709:Biotechnology; D003227:Conjugation, Genetic; D003890:Desiccation; D017753:Ecosystem; D008957:Models, Genetic; D010957:Plasmids / Q000235:genetics*; D016958:Pseudomonas putida / Q000235:genetics / Q000502:physiology; D012240:Rhodococcus / Q000235:genetics / Q000502:physiology; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000302:isolation & purification / Q000378:metabolism
D012989:Soil Pollutants