Plasmid-encoded phthalate catabolic pathway in Arthrobacter keyseri 12B.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Phthalate catabolism is a key microbial process.
• Arthrobacter keyseri possesses enzymes for phthalate degradation.
• Understanding these pathways can aid in bioremediation and genetic engineering.

Purpose of the Study:

• To identify and characterize genes involved in phthalate catabolism from Arthrobacter keyseri.
• To elucidate the enzymatic steps in the conversion of phthalates to protocatechuates.
• To develop a screening method for identifying relevant genes in recombinant organisms.

Main Methods:

• Enzymatic conversion of substituted benzoates by Arthrobacter keyseri.
• Chromogenic assay using iron-containing medium.
• Cloning and DNA sequencing of genes from plasmid pRE1.
• Restriction mapping and functional analysis of genetic units.

Main Results:

• 2-substituted benzoates were converted to 2-substituted 3,4-dihydroxybenzoates (protocatechuates).
• Accumulated protocatechuates formed colored chelates, enabling a chromogenic screen.
• Genes encoding phthalate 3,4-dioxygenase and dehydrogenase were identified and sequenced.
• The pht operon responsible for phthalate to protocatechuate conversion was characterized, along with other genetic units.

Conclusions:

• A novel chromogenic method was established for identifying genes involved in phthalate catabolism.
• The genetic organization and sequence of the phthalate catabolic pathway (pht operon) in Arthrobacter keyseri were elucidated.
• Recombinant E. coli strains expressing these genes demonstrated enzymatic activities, confirming their roles in the pathway.