Conjugative transfer of preferential utilization of aromatic compounds from Pseudomonas putida CSV86

Area of Science:

• Microbial metabolism and genetics
• Environmental microbiology
• Bacterial conjugation

Background:

• Pseudomonas putida CSV86 exhibits preferential utilization of aromatic compounds (naphthalene, salicylate, benzyl alcohol, methylnaphthalene) over glucose.
• Methylnaphthalene degradation occurs via both ring- and side-chain hydroxylation pathways.
• A stable degradation property was observed, but a loss-of-function phenotype (Nap(-)Sal(-)MN(-)Balc(-)) emerged under specific conditions.

Purpose of the Study:

• To investigate the mechanism behind the preferential aromatic compound utilization in Pseudomonas putida CSV86.
• To determine if this metabolic property is transferable to other bacterial species.
• To identify the genetic basis for the observed degradation and preferential utilization pathways.

Main Methods:

• Conjugation experiments were performed to transfer the degradation property from P. putida CSV86 to Stenotrophomonas maltophilia CSV89.
• Phenotypic analysis of donor and transconjugant strains for aromatic compound utilization.
• PCR amplification using specific primers for dioxygenase genes and DNA-DNA hybridization were employed to confirm gene transfer.

Main Results:

• The aromatic compound degradation and preferential utilization property was successfully transferred to S. maltophilia CSV89 via conjugation.
• Transconjugants metabolized methylnaphthalene via both ring- and side-chain hydroxylation pathways, similar to the donor strain.
• The transferred properties were lost upon prolonged cultivation on glucose or 2YT medium, and no plasmid DNA was detected.

Conclusions:

• A probable conjugative element, likely not a plasmid, is involved in the metabolism of aromatic compounds and their preferential utilization over glucose.
• This element mediates both ring- and side-chain hydroxylation pathways for methylnaphthalene degradation.
• The instability of the transferred trait, particularly its loss on glucose, suggests complex regulatory mechanisms or integration/excision events.