USE OF DNA PROBES AND PLASMID CAPTURE IN A SEARCH FOR NEW INTERESTINGENVIRONMENTAL GENES

Adaptation to a stressed environment leads to organisms bearing DNA, e ncoding defense mechanisms. These mechanisms can be heavy metal resist ance, catabolism of organic xenobiotics or stress reactions. Genes res ponsible for these mechanisms can be used for monitoring changing envi ronments and therefore it can be important to store such bacteria in a bank. DNA-probing will be presented by the use of DNA fragments (of A lcaligenes eutrophus) coding for heavy metal resistance or xenobiotic degradation. Some strains do not grow on petri dishes and accordingly cannot be isolated from soils. In order to isolate plasmids from such strains, coding for heavy metal resistances or xenobiotic degradations , an exogenous plasmid isolation method was developed. In this method, the endogenous population is conjugated with Pseudomonas or Alcaligen es strains bearing a retrotransfer plasmid like RP4. In that way new p lasmids from various sources including non-culturable strains could be obtained. With these methods, a large number of specimens adapted to stressed situations can be isolated or constructed (in the case of the exogenous plasmid isolation method). They form a source of interestin g genetic material that can be used to restore polluted areas in natur al areas, if necessary with the aid of genetic engineering (in vitro o r in vivo techniques). Full knowledge of such bacteria and their resis tance mechanisms or degradation pathways, can lead to new construction s able to attack recalcitrant mixtures of different organics and to re sist heavy metals.