title: High polyhydroxybutyrate production in Pseudomonas extremaustralis is associated with differential expression of horizontally acquired and core genome polyhydroxyalkanoate synthase genes.
abstract: Pseudomonas extremaustralis produces mainly polyhydroxybutyrate (PHB), a short chain length polyhydroxyalkanoate (sclPHA) infrequently found in Pseudomonas species. Previous studies with this strain demonstrated that PHB genes are located in a genomic island. In this work, the analysis of the genome of P. extremaustralis revealed the presence of another PHB cluster phbFPX, with high similarity to genes belonging to Burkholderiales, and also a cluster, phaC1ZC2D, coding for medium chain length PHA production (mclPHA). All mclPHA genes showed high similarity to genes from Pseudomonas species and interestingly, this cluster also showed a natural insertion of seven ORFs not related to mclPHA metabolism. Besides PHB, P. extremaustralis is able to produce mclPHA although in minor amounts. Complementation analysis demonstrated that both mclPHA synthases, PhaC1 and PhaC2, were functional. RT-qPCR analysis showed different levels of expression for the PHB synthase, phbC, and the mclPHA synthases. The expression level of phbC, was significantly higher than the obtained for phaC1 and phaC2, in late exponential phase cultures. The analysis of the proteins bound to the PHA granules showed the presence of PhbC and PhaC1, whilst PhaC2 could not be detected. In addition, two phasin like proteins (PhbP and PhaI) associated with the production of scl and mcl PHAs, respectively, were detected. The results of this work show the high efficiency of a foreign gene (phbC) in comparison with the mclPHA core genome genes (phaC1 and phaC2) indicating that the ability of P. extremaustralis to produce high amounts of PHB could be explained by the different expression levels of the genes encoding the scl and mcl PHA synthases.
authors.affiliation: Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Mariela V
authors.initials: MV
authors.lastname: Catone
authors.affiliation: Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Investigaciones en Biociencias Agrícolas y Ambientales, CONICET, Buenos Aires, Argentina.
authors.forename: Jimena A
authors.initials: JA
authors.lastname: Ruiz
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
authors.forename: Mildred
authors.initials: M
authors.lastname: Castellanos
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
authors.forename: Daniel
authors.initials: D
authors.lastname: Segura
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Espin
authors.affiliation: Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; IQUIBICEN, CONICET, Buenos Aires, Argentina.
authors.forename: Nancy I
authors.initials: NI
authors.lastname: López
mesh_terms: D000217:Acyltransferases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D006885:Hydroxybutyrates / Q000378:metabolism*; D011549:Pseudomonas / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D006885:Hydroxybutyrates; D000217:Acyltransferases; C077225:poly(3-hydroxyalkanoic acid) synthase