The impact of flow rate (simulated leaching) on plasmid transfer frequencybetween bacteria in a model rhizosphere system

Aims: To investigate the effect of flow rate and inoculation order on plasm id transfer frequency between bacteria in a model rhizosphere system. Methods and Results: A physical model system was constructed and used to de monstrate that although flow rate did affect plasmid transfer frequency for an introduced strain, the flow; rates necessary for a significant effect o n an established population were much higher than typical water flow rates found through soil. Plasmid transfer frequency was highly sensitive to stra in inoculation order. Conclusion: Flow rate may not have a significant effect on plasmid transfer frequency between established bacterial populations in the rhizosphere. Significance and Impact of Study: This study contributes to the current deb ate over the release and spread of genetically modified organisms into the environment. It also demonstrates that model controlled systems may be used to rapidly obtain initial data about the potential behaviour of microorgan isms, prior to more costly and lengthy glasshouse and held trials.