title: Bacterial chitinase with phytopathogen control capacity from suppressive soil revealed by functional metagenomics.
abstract: Plant disease caused by fungal pathogens results in vast crop damage globally. Microbial communities of soil that is suppressive to fungal crop disease provide a source for the identification of novel enzymes functioning as bioshields against plant pathogens. In this study, we targeted chitin-degrading enzymes of the uncultured bacterial community through a functional metagenomics approach, using a fosmid library of a suppressive soil metagenome. We identified a novel bacterial chitinase, Chi18H8, with antifungal activity against several important crop pathogens. Sequence analyses show that the chi18H8 gene encodes a 425-amino acid protein of 46 kDa with an N-terminal signal peptide, a catalytic domain with the conserved active site F175DGIDIDWE183, and a chitinase insertion domain. Chi18H8 was expressed (pGEX-6P-3 vector) in Escherichia coli and purified. Enzyme characterization shows that Chi18H8 has a prevalent chitobiosidase activity with a maximum activity at 35 °C at pH lower than 6, suggesting a role as exochitinase on native chitin. To our knowledge, Chi18H8 is the first chitinase isolated from a metagenome library obtained in pure form and which has the potential to be used as a candidate agent for controlling fungal crop diseases. Furthermore, Chi18H8 may also answer to the demand for novel chitin-degrading enzymes for a broad range of other industrial processes and medical purposes.
authors.forename: Karin
authors.initials: K
authors.lastname: Hjort
authors.forename: Ilaria
authors.initials: I
authors.lastname: Presti
authors.forename: Annelie
authors.initials: A
authors.lastname: Elväng
authors.forename: Flavia
authors.initials: F
authors.lastname: Marinelli
authors.forename: Sara
authors.initials: S
authors.lastname: Sjöling
mesh_terms: D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D002686:Chitin / Q000378:metabolism; D002688:Chitinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005658:Fungi / Q000187:drug effects*; D015870:Gene Expression; D015723:Gene Library; D006863:Hydrogen-Ion Concentration; D056186:Metagenomics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D002686:Chitin; D002688:Chitinases