title: Heterologous expression of pyrroloquinoline quinone (pqq) gene cluster confers mineral phosphate solubilization ability to Herbaspirillum seropedicae Z67.
abstract: Gluconic acid secretion mediated by the direct oxidation of glucose by pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (GDH) is responsible for mineral phosphate solubilization in Gram-negative bacteria. Herbaspirillum seropedicae Z67 (ATCC 35892) genome encodes GDH apoprotein but lacks genes for the biosynthesis of its cofactor PQQ. In this study, pqqE of Erwinia herbicola (in plasmid pJNK1) and pqq gene clusters of Pseudomonas fluorescens B16 (pOK53) and Acinetobacter calcoaceticus (pSS2) were over-expressed in H. seropedicae Z67. Transformants Hs (pSS2) and Hs (pOK53) secreted micromolar levels of PQQ and attained high GDH activity leading to secretion of 33.46 mM gluconic acid when grown on 50 mM glucose while Hs (pJNK1) was ineffective. Hs (pJNK1) failed to solubilize rock phosphate, while Hs (pSS2) and Hs (pOK53) liberated 125.47 μM and 168.07 μM P, respectively, in minimal medium containing 50 mM glucose under aerobic conditions. Moreover, under N-free minimal medium, Hs (pSS2) and Hs (pOK53) not only released significant P but also showed enhanced growth, biofilm formation, and exopolysaccharide (EPS) secretion. However, indole acetic acid (IAA) production was suppressed. Thus, the addition of the pqq gene cluster, but not pqqE alone, is sufficient for engineering phosphate solubilization in H. seropedicae Z67 without compromising growth under nitrogen-fixing conditions.
authors.affiliation: Molecular Microbial Biochemistry Laboratory, Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, 390 002, India.
authors.forename: Jitendra
authors.initials: J
authors.lastname: Wagh
authors.forename: Sonal
authors.initials: S
authors.lastname: Shah
authors.forename: Praveena
authors.initials: P
authors.lastname: Bhandari
authors.forename: G
authors.initials: G
authors.lastname: Archana
authors.forename: G Naresh
authors.initials: GN
authors.lastname: Kumar
mesh_terms: D016954:Acinetobacter calcoaceticus / Q000201:enzymology / Q000235:genetics; D053898:Biosynthetic Pathways / Q000235:genetics*; D004885:Erwinia / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D042803:Herbaspirillum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D060847:Metabolic Engineering; D008903:Minerals / Q000378:metabolism*; D005810:Multigene Family; D045542:PQQ Cofactor / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D008903:Minerals; D010710:Phosphates; D011994:Recombinant Proteins; D045542:PQQ Cofactor