title: Identification and characterization of genes underlying chitinolysis in Collimonas fungivorans Ter331.
abstract: Through a combinatorial approach of plasposon mutagenesis, genome mining, and heterologous expression, we identified genes contributing to the chitinolytic phenotype of bacterium Collimonas fungivorans Ter331. One of five mutants with abolished ability to hydrolyze colloidal chitin carried its plasposon in the chiI gene coding for an extracellular endochitinase. Two mutants were affected in the promoter of chiP-II coding for an outer-membrane transporter of chitooligosaccharides. The remaining two mutations were linked to chitobiose/N-acetylglucosamine uptake. Thus, our model for the Collimonas chitinolytic system assumes a positive feedback regulation of chitinase activity by chitin degradation products. A second chitinase gene, chiII, coded for an exochitinase that preferentially released chitobiose from chitin analogs. Genes hexI and hexII showed coding resemblance to N-acetylglucosaminidases, and the activity of purified HexI protein towards chitin analogs suggested its role in converting chitobiose to N-acetylglucosamine. The hexI gene clustered with chiI, chiII, and chiP-II in one locus, while chitobiose/N-acetylglucosamine uptake genes colocalized in another. Both loci contained genes for conversion of N-acetylglucosamine to fructose-6-phosphate, confirming that C. fungivorans Ter331 features a complete chitin pathway. No link could be established between chitinolysis and antifungal activity of C. fungivorans Ter331, suggesting that the bacterium's reported antagonism towards fungi relies on other mechanisms.
authors.affiliation: Netherlands Institute of Ecology (NIOO-KNAW), Heteren, The Netherlands.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Fritsche
authors.forename: Wietse
authors.initials: W
authors.lastname: de Boer
authors.forename: Saskia
authors.initials: S
authors.lastname: Gerards
authors.forename: Marlies
authors.initials: M
authors.lastname: van den Berg
authors.forename: Johannes A
authors.initials: JA
authors.lastname: van Veen
authors.forename: Johan H J
authors.initials: JH
authors.lastname: Leveau
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002686:Chitin / Q000378:metabolism*; D002688:Chitinases / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004187:Disaccharides / Q000378:metabolism; D005636:Fructosephosphates / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006596:Hexosaminidases / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D042802:Oxalobacteraceae / Q000235:genetics*; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004187:Disaccharides; D005636:Fructosephosphates; D002686:Chitin; C032438:chitobiose; C027618:fructose-6-phosphate; C079639:1,4-beta-chitobiosidase; D006596:Hexosaminidases; D002688:Chitinases; D000117:Acetylglucosamine