MOBILIZATION OF BROAD-HOST-RANGE PLASMID FROM PSEUDOMONAS-PUTIDA TO ESTABLISHED BIOFILM OF BACILLUS AZOTOFORMANS - II - MODELING

A strain of Pseudomonas putida that harbors plasmids RK2 and pDLB101 w as exposed to a pure culture biofilm of Bacillus azotoformans grown in a rotating annular reactor. Transfer of the RK2 mobilizable pDLB101 p lasmid to B. azotoformans was monitored over a 4-day period. Experimen tal results demonstrated that the broad host range, RSF1010 derivative pDLB101 was transferred to and expressed by B. azotoformans. In the c ompanion article to th is work, the rate of plasmid transfer was quant ified as a function of the limiting nutrient, succinate, and as a func tion of the mechanism of transfer. A biofilm process simulation progra m (AQUASIM) was modified to analyze resultant experimental data. Al th ough the AQUASIM package was not designed to simulate or predict genet ic events in biofilms, modification of the rate process dynamics allow ed successful modeling of plasmid transfer. For the narrow range of su bstrate concentrations used in these experiments, nutrient level had o nly a slight effect on the rate and extent of plasmid transfer in biof ilms. However, further simulations using AQUASIM revealed that under n utrient poor conditions, the number of transconjugants appearing in th e biofilm was limited. (C) 1998 John Wiley & Sons, Inc.