Improving the catabolic functions of desiccation-tolerant soil bacteria

Bacterial strains were selected from a desiccated polluted soil for their d rought tolerance and their ability to grow on diesel oil in view of incorpo rating them in a bioaugmentation product. These products are useful in ease of recalcitrant xenobiotic pollution, where there is no intrinsic biodegra dation activity in the soil. These strains grow on the easily degradable co mponents of diesel oil. Introduction of new catabolic genes into these desi ccation-tolerant bacteria in order to improve their catabolic functions was considered. Plasmid-borne catabolic genes coding for enzymes involved in the degradatio n of more recalcitrant compounds (Isopropylbenzene, trichloroethene, 3-chlo robenzoate,4-chlorobiphenyl, biphenyl) were successfully introduced in some of the desiccation-tolerant strains by means of natural conjugation. Strai ns exhibiting good tolerance to desiccation and able to grow on the new car bon sources were obtained. The frequencies of integration of the plasmids r anged from 2 x 10(-8) to 9.2 10(-2) transconjugants/acceptor. Drought-tolerance is indeed important for bioaugmentation because of its in trinsic ecological significance and because a bioaugmentation starter has t o be conditioned in a desiccated form to ensure good shelf-life. The conser vation of the properties during storage was evaluated by accelerated storag e tests.