Open AccessBiochemical and Genetic Analysis of the γ-Resorcylate (2,6-Dihydroxybenzoate) Catabolic Pathway in Rhizobium sp. Strain MTP-10005: Identification and Functional Analysis of Its Gene Cluster
Author(s) -
Masahiro Yoshida,
Tadao Oikawa,
Hitoshi Obata,
Katsumasa Abe,
Hisaaki Mihara,
Nobuyoshi Esaki
Publication year - 2007
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01675-06
Subject(s) - biology , operon , gene cluster , gene , rhizobium , transcription (linguistics) , escherichia coli , reductase , microbiology and biotechnology , plasmid , catabolism , gene expression , biochemistry , enzyme , linguistics , philosophy
We identified a gene cluster that is involved in the γ-resorcylate (2,6-dihydroxybenzoate) catabolism of the aerobic bacteriumRhizobium sp. strain MTP-10005. The cluster consists of thegraRDAFCBEK genes, andgraA ,graB ,graC , andgraD were heterologously expressed inEscherichia coli . Enzymological studies showed thatgraD ,graA ,graC , andgraB encode the reductase (GraD) and oxygenase (GraA) components of a resorcinol hydroxylase (EC 1.14.13.x), a maleylacetate reductase (GraC) (EC 1.3.1.32), and a hydroxyquinol 1,2-dioxygenase (GraB) (EC 1.13.11.37). Bioinformatic analyses suggested thatgraE ,graR , andgraK encode a protein with an unknown function (GraE), a MarR-type transcriptional regulator (GraR), and a benzoate transporter (GraK). Quantitative reverse transcription-PCR ofgraF , which encodes γ-resorcylate decarboxylase, revealed that the maximum relative mRNA expression level ([5.93 ± 0.82] × 10−4 ) ofgraF was detected in the total RNA of the cells after one hour of cultivation when γ-resorcylate was used as the sole carbon source. Reverse transcription-PCR ofgraDAFCBE showed that these genes are transcribed as a single mRNA and that the transcription of the gene cluster is induced by γ-resorcylate. These results suggested that thegraDAFCBE genes are responsible as an operon for the growth ofRhizobium sp. strain MTP-10005 on γ-resorcylate and are probably regulated by GraR at the transcriptional level. This is the first report of the γ-resorcylate catabolic pathway in an aerobic bacterium.