The ortho-phenylphenol degrading Sphingomonas haloaromaticamans strain P3

Ortho-phenylphenol (OPP) is a fungicide widely used by the fruit packaging industry to prevent post-harvest infestation during storage. A Sphingomonas haloaromaticamans strain P3 was previously isolated as an OPP degrader from a contaminated soil in Greece. To explore the OPP catabolic pathway a genomic-proteomic approach was followed. Four catabolic operons with a putative role in OPP metabolism were identified via genomic analysis. A complete OPP-operon with genes responsible for the transformation of OPP to benzoic acid (BA) and 2-hydroxypenta-2,4-dienoate, a ben/cat and a complete bph operon which convert the above metabolites to Krebs cycle intermediates were identified in scaffold3. A second ben/cat operon was identified in scaffold1. Comparative proteomic analysis revealed over 200 genes differentially regulated in the presence of OPP, BA or succinate. Different over-expressed proteins with putative role in OPP degradation were identified, showing their highest homology to genes of scaffold3. Transcriptional analysis of the putative catabolic genes further confirm the specific activation of operons of scaffold3 during OPP degradation, while a weak up-regulation of the ben/cat operon of scaffold1 was observed only when the bacterium was grown on BA. The loss of degrading ability in plasmid cured cells indicate a possible plasmidic location of scaffold3.