Phenolic compound degradation by Pseudomonas syringae phylogroup 2 strains

Abstract

It has recently been shown that Pseudomonas syringae strains pathogenic to woody hosts belonging to phylogroup (PG) 2 lack phenolic compound degradation pathways such as the beta-ketoadipate and protocatechuate pathways. The aim of this study was to analyse a selection of P. syringae PG 2 genomes, including those used previously to determine if they had other phenolic compound degradation pathways and to determine whether or not they were functional. Twenty-one publicly available genomes of PG 2 strains were analyzed. These strains had previously been isolated from both woody and herbaceous hosts. Phenolic degradation enzymes were present in 5 (23%) of the strains analysed, originating from both woody and herbaceous hosts. Hypothetical pathways were proposed to determine if catechol, anthranilate and benzoic acid were degraded by these strains. Both spectrophotometric and HPLC were used to determine phenolic compound degradation. The five strains with phenolic degradation enzymes were able to metabolize catechol, and HRI-W 7924 and MAFF 301072 could also metabolize anthranilate and benzoate, respectively. The study showed that even though some PG 2 strains lack the beta-ketoadipate and protocatechuate pathways, they still have phenolic compound degrading enzymes that may play a role in virulence.