In pursuit of developing an oil-degrading microbial consortium, we used the principle of "plasmid assisted molecular breeding" (PAMB) in a continuous culture system. Three marine bacteria, Pseudomonas putida, Brevibacterium epidermidis and Pseudomonas diminuta, with distinct colony traits, growth rates, and crude oil-degrading abilities (75, 74 and 60% respectively at 1% v/v concentration) were examined for changes functional role in a continuous culture system. The changes observed in the ratio from 4:2:1 through the experimental period are discussed. Pseudomonas putida increased in number in the first 15 days and declined thereafter with a concomitant 10-fold increase in P. diminuta population as observed on day 24. This reversal in trend of the least dominant strain evolging as the most predominant one is highlighted, together with the total oil degradation and emulsifying activity in continuous culture