Polyethylene Terephthalate (PET) Primary Degradation Products Affect c-di-GMP-, cAMP-Signaling, and Quorum Sensing (QS) in Vibrio gazogenes DSM 21264

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Global plastic pollution in oceans and estuaries is increasing rapidly and it’s well known that bacteria colonize plastic particles of all sizes. _Vibri_o spp. are frequently found as part of the plastisphere. We recently showed that _Vibrio gazogenes_ DSM 21264 harbors a promiscuous esterase designated PET6. We now provide evidence that the _pet6_ gene is expressed under a wide range of environmental conditions in its native host. However, in PET- and PE-grown biofilms the _pet6_ gene expression was not affected by the type of surface. The _pet6_ transcription was sufficient to allow enzyme production and release of µM amounts of mono-(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid (TPA) already after 24 hours of incubation on PET foil. Notably, the highest _pet6_ gene transcription was observed in planktonic lifestyle in the presence of bis(2-hydroxyethyl) terephthalate (BHET) one of the primary degradation products of PET. BHET was further hydrolyzed by PET6 and UlaG, a lactonase that had not been known to be involved in BHET degradation. Elevated concentrations of BHET affected the major signaling circuits involved in bacterial quorum sensing (QS), c-di-GMP and cAMP-CRP signaling. This resulted in failure to form biofilms, synthesis of the red pigment prodigiosin and altered colony morphologies. While BHET had a very wide impact, TPA interfered mainly with the bacterial QS by attenuating the expression of the CAI-I autoinducer synthase gene. These observations imply a potential role of BHET and TPA as nutritional signals in _Vibrio gazogenes_ and that may affect its growth and survival in the plastisphere. IMPORTANCE: This study provides first evidence that _Vibrio gazogenes_ DSM 21264 secretes an active PET hydrolase and degrades the polymer using PET6 when growing in biofilms on foils and microplastic particles. The study further provides evidence that the primary PET degradation products BHET and TPA may have a profound impact on the global QS, c-di-GMP and cAMP-CRP signaling of _V. gazogenes_ and its capability to colonize plastic particles in the marine environment.

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