Proteogenomic Characterization of Pseudomonas veronii SM-20 Growing on Phenanthrene as Only Carbon and Energy Source.

In this study, we conducted an extensive investigation of the biodegradation capabilities and stress response of the newly isolated strain Pseudomonas veronii SM-20 in order, to assess its potential for bioremediation of sites contaminated with polycyclic aromatic hydrocarbons (PAHs). Initially, phenotype microarray technology demonstrated the strain's proficiency in utilizing various carbon sources and its resistance to certain stressors. Genomic analysis has identified numerous genes involved in aromatic hydrocarbon metabolism. Biodegradation assay analyzed the depletion of phenanthrene (PHE) when it was added as a sole carbon and energy source. We found that P. veronii strain SM-20 degraded approximately 25% of PHE over a 30-day period, starting with an initial concentration of 600 µg/mL, while being utilized for growth. The degradation process involved PHE oxidation to an unstable arene oxide and 9,10-phenanthrenequinone, followed by ring-cleavage. Comparative proteomics provided a comprehensive understanding of how the entire proteome responded to PHE exposure, revealing the strain's adaptation in terms of aromatic metabolism, surface properties, and defense mechanism. In conclusion, our findings shed light on the promising attributes of P. veronii SM-20 and offer valuable insights for the use of P. veronii species in environmental restoration efforts targeting PAH-impacted sites.

A global survey reveals a divergent extradiol dioxygenase clade as a widespread complementary contributor to the biodegradation of mono- and polycyclic aromatic hydrocarbons.

Extradiol dioxygenation is a key reaction in the microbial aerobic degradation of mono- and polycyclic aromatic hydrocarbon catecholic derivatives. It has been reported that many bacterial enzymes exhibiting such converging functions act on a wide range of catecholic substrates. The present study reports a new subfamily of extradiol dioxygenases (EXDOs) with broad substrate specificity, the HrbC EXDOs. The new clade belongs to the XII cluster within family 2 of the vicinal oxygen chelate superfamily (EXDO-VC2), which is typically characterized by a preference for bicyclic substrates. Coding hrbC orthologs were isolated by activity-based screening of fosmid metagenomic libraries from large DNA fragments derived from heavily PAH-contaminated soils. They occurred as solitary genes within conserved sequences encoding enzymes for amino acid metabolism and were stably maintained in the chromosomes of the Betaproteobacteria lineages harboring them. Analysis of contaminated aquifers revealed coexpression of hrbC as a polycistronic mRNA component. The predicted open reading frames were verified by cloning and heterologous expression, confirming the expected molecular mass and meta-cleavage activity of the recombinant enzymes. Evolutionary analysis of the HrbC protein sequences grouped them into a discrete cluster of 1,2-dihydroxynaphthalene dioxygenases represented by a cultured PAH degrader, Rugosibacter aromaticivorans strain Ca6. The ecological importance and relevance of the new EXDO genes were confirmed by PCR-based mapping in different biogeographical localities contaminated with a variety of mono- and polycyclic aromatic compounds. The cosmopolitan distribution of hrbC in PAH-contaminated aquifers supports our hypothesis about its auxiliary role in the degradation of toxic catecholic intermediates, contributing to the composite EXDO catabolic capacity of the world's microbiomes.