Phenolic compound degradation by Pseudomonas syringae
phylogroup 2 strains
Teresa Ann Coutinho
Published online: 4 June 2018
Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2018
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.
Keywords Pseudomonas syringae
Bacterial species belonging to the Pseudomonas syringae
complex cause disease on several herbaceous and woody
hosts (Lamichhane et al., 2014, 2015). This bacterial spe-
cies is considered one of the most economically important
pathogens and it has been extensively used to model
plant-pathogen interactions (Mansfield et al., 2012). Even
though most of the research on this pathogen was focused
on herbaceous hosts, several recent studies have investigat-
ed the molecular basis of virulence on woody hosts
(Green et al., 2010;Lamichhaneetal.,2014; Nowell et
al., 2016; Caballo-Ponce et al., 2017).
Several factors have been identified to be of importance for
virulence of P. syringae on woody hosts, such as metabolic
pathways involved in the degradation of phenolic compounds
(Green et al., 2010; Nowell et al., 2016). These pathways
include the beta-ketoadipate and protocatechute pathways.
Both pathways have been well characterized bioinformatically
in the chestnut pathogen, Pseudomonas syringae pv. aesculi,
and are involved in the degradation of protocatechuate and
catechol to tricarboxylic acid cycle intermediates, respectively
(Green et al., 2010; Harwood and Parales, 2003).
Nine genomospecies were identified in the P. syringae
complex based on DNA:DNA hybridization (DDH) (Gardan
et al., 1999). Average nucleotide analyses (ANI) (Marcelletti
and Scortichini, 2014) confirmed the existence of the majority
of these genomospecies (gs), with the exception of gs 3 and 8.
Recently, Berge et al. (2014) described the presence of 13
phylogroups using Multilocus Sequence Analyses (MLSA)
of concatenated housekeeping genes including cts, gapA,
gyrB and rpoD which largely correspond to the nine
genomospecies defined by Gardan et al. (1999).
* Teresa Ann Coutinho
Department of Microbiology and Plant Pathology, Forestry and
Agricultural Biotechnology Institute, University of Pretoria, Private
Bag X20, Pretoria 00282, South Africa
Department of Zoology and Entomology, Forestry and Agricultural
Biotechnology Institute, University of Pretoria, Private Bag X20,
Pretoria 00282, South Africa
Agricultural Research Council, Infruitec-Nietvoorbij, Private Bag
X5026, Stellenbosch 7599, South Africa
Centre for Bioinformatics and Computational Biology, Department
of Biochemistry, Faculty of Natural and Agricultural Sciences,
University of Pretoria, Private Bag X20, Pretoria 00282, South Africa
Journal of Plant Pathology (2018) 100:279–286