title: The loss of function of PhaC1 is a survival mechanism that counteracts the stress caused by the overproduction of poly-3-hydroxyalkanoates in Pseudomonas putidaΔfadBA.
abstract: The poly-3-hydroxylkanoate (PHA)-overproducing mutant Pseudomonas putida U ΔfadBA (PpΔfadBA) lacks the genes encoding the main β-oxidation pathway (FadBA). This strain accumulates enormous amounts of bioplastics when cultured in chemically defined media containing PHA precursors (different n-alkanoic or n-aryl-alkanoic acids) and an additional carbon source. In medium containing glucose or 4-hydroxy-phenylacetate, the mutant does not accumulate PHAs and grows just as the wild type (P. putida U). However, when the carbon source is octanoate, growth is severely impaired, suggesting that in PpΔfadBA, the metabolic imbalance resulting from a lower rate of β-oxidation, together with the accumulation of bioplastics, causes severe physiological stress. Here, we show that PpΔfadBA efficiently counteracts this latter effect via a survival mechanism involving the introduction of spontaneous mutations that block PHA accumulation. Surprisingly, genetic analyses of the whole pha cluster revealed that these mutations occurred only in the gene encoding one of the polymerases (phaC1) and that the loss of PhaC1 function was enough to prevent PHA synthesis. The influence of these mutations on the structure of PhaC1 and the existence of a protein-protein (PhaC1-PhaC2) interaction that explains the functionality of the polymerization system are discussed herein.
authors: Departamento de Biología Molecular, Facultad de Veterinaria, Universidad de León, León, 24071, Spain.
authors: José I
authors: JI
authors: Obeso
authors: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, Alicante, 03202, Spain.
authors: Beatriz
authors: B
authors: Maestro
authors: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Elche, Alicante, 03202, Spain.
authors: Jesús M
authors: JM
authors: Sanz
authors: Departamento de Biología Molecular, Facultad de Veterinaria, Universidad de León, León, 24071, Spain.
authors: Elías R
authors: ER
authors: Olivera
authors: Departamento de Biología Molecular, Facultad de Veterinaria, Universidad de León, León, 24071, Spain.
authors: José M
authors: JM
authors: Luengo
mesh_terms: D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D063566:Biodegradable Plastics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002210:Caprylates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D010648:Phenylacetates / Q000378:metabolism; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D016958:Pseudomonas putida / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D063566:Biodegradable Plastics; D002210:Caprylates; D010648:Phenylacetates; D054813:Polyhydroxyalkanoates; C026246:4-hydroxyphenylacetate; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase; D005947:Glucose; C031492:octanoic acid