Molecular breeding of oil degrading microorganisms: Development of phenol degrading mutant of Pseudomonas cepacia AC1100

Abstract

Among the large number of toxic constituents of heavier fractions of crude oil, phenols, cresols, xylenols and naphthols are prominent aromatic members. The genome of Pseudomonas cepacia AC1100 is a reservoir of several translocating insertion elements that have gene regulatory functions. It is also encoding genes for catabolism of chlorinated analogues of phenoxyacetic acid and chlorophenols via a unique pathway that has chlorohydroxy-hydroquinone as the key intermediate. On long-term enrichment with phenoxyacetic acid, we could develop a mutant of P. cepacia which had acquired the ability to utilize phenol. Evidence is provided indicating that phenol induces the enzymes for its degradation via meta-pathway that converges on the pathway of benzoate metabolism. These enzymes were not functional in the wild type AC1100. Results of complementation studies involving introduction of cloned degradative genes for chloroaromatics into mutants of P. cepacia which were defective in acquiring phenol degrading ability, suggest that there may be possibility of closer links of meta-pathway genes with the genetic material encoding degradation of chlorinated analogues.