Abstract

In this investigation we tried to transfer plasmid encoded silver and antibiotic resistance genes from Acinetobacter baumannii BL54 to E. coli k12 J53.2 and Pseudomonas (a soil microflora) by conjugation and transformation in different soil microcosms and study the survival of the isolated bacterium in each soil. Clay loam, fine clay, sandy and clay soils were collected from different area of mahrashtra in India. Microcosm was developed for each type of soil in the glass tube (150 x 25 mm) with 2 g soil moistened with 1 ml 0.5% sterile saline. The conjugation frequency was lowest in sterile clay soil with frequency of 0.2 x 10^-6, while, it was maximum in clay loam soil with frequency of 0.6 x 10^-6. Similarly, in non-sterile soil microcosms, the rate of conjugation was highest in clay loam soil with frequency of 0.09 x 10^-6 while was lowest in sandy soil (0.03 x 10^-6). Rapid death of the organisms was observed within 9 days of incubation in presence of selection in sandy soil, while in fine clay, survival of the organisms was extended beyond 11 days. The Pseudomonas transformant survived for more than 40 days in presence of selection. From above results it can be concluded that plasmid mediated silver and antibiotic resistant genes were transferred in different soil by conjugation process. However, the rate of conjugation was affected by soil type. Soil transformant considerably survived in fine clay containing high amount of organic carbon and neutral pH as compared to sandy soil.  

Key words: Conjugation, soil type, survival, plasmid, Acinetobacter baumannii.