The bio operon on the acquired symbiosis island of Mesorhizobium sp. strain R7A includes a novel gene involved in pimeloyl-CoA synthesis

• Published in: Microbiology (Society for General Microbiology) Vol. 147; no. 5; pp. 1315 - 1322
• Main Authors: Sullivan, John T, Brown, Steven D, Yocum, R. Rogers, Ronson, Clive W
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.05.2001; Society for General Microbiology
• Subjects: Acyl Coenzyme A - biosynthesis; Acyltransferases - genetics; Acyltransferases - metabolism; Amino Acid Sequence; Bacterial Proteins - genetics; Bacteriology; beta -Ketoacyl-acyl carrier protein synthase III; bioA gene; bioBFD gene; Biological and medical sciences; Biotin - biosynthesis; bioZ gene; DNA Transposable Elements; Freshwater; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Genetic Complementation Test; Genetics; Lotus corniculatus; Mesorhizobium; Microbiology; Molecular Sequence Data; Mutagenesis, Insertional; nadABC gene; Niacin - biosynthesis; nifA gene; Nitrogen Fixation - genetics; Operon; panD gene; Plants - microbiology; Rhizobiaceae - genetics; Rhizobiaceae - growth & development; Rhizobiaceae - metabolism; Sequence Alignment; Sequence Analysis, DNA; Symbiosis; Thiamine - biosynthesis; Transcription Factors - genetics; Vitamins - biosynthesis; Symbiosis; Nucleotide sequence; Enzyme; Operon; Lotus corniculatus; Vitamin; Vegetal microorganism relation; Homology; Gene organization; Biosynthesis; Biotin; Leguminosae; Dicotyledones; Angiospermae; Bacteria; Spermatophyta; Biosynthesis precursor; Fodder crop; Rhizobiaceae; Aminoacid sequence; Nicotinic acid derivatives
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/00221287-147-5-1315

Department of Microbiology, University of Otago, PO Box 56, Dunedin, New Zealand 1 OmniGene Bioproducts Inc., Cambridge, MA 02138, USA 2 Author for correspondence: Clive W. Ronson. Tel: +64 3 4797701. Fax: +64 3 4798540. e-mail: clive.ronson{at}stonebow.otago.ac.nz The symbiosis island of Mesorhizobium sp. strain R7A is a 500 kb chromosomal genetic element that upon transfer converts nonsymbiotic mesorhizobia to symbionts able to nodulate and fix nitrogen with Lotus corniculatus . Four genomic species of nonsymbiotic mesorhizobia have been isolated. All were auxotrophic for thiamin and biotin and three were auxotrophic for nicotinate, whereas derivatives of the strains containing the symbiosis island were prototrophic for all three vitamins. In this work, a 13·2 kb region of the island that converts the nonsymbionts to nicotinate and biotin prototrophy was characterized. The region contained orthologues of the Escherichia coli bioBFD and A genes arranged in an operon with a novel gene, bioZ , a nadABC operon, the nitrogen-fixation regulatory gene nifA , and a homologue of the pantothenate biosynthesis gene panD . The bioZ gene product was similar toß-ketoacyl-acyl carrier protein synthase III (FabH). bioZ ::Tn 5 mutants grew poorly in the absence of biotin and the bioZ gene complemented an E. coli bioH mutant, suggesting that its product is involved in the synthesis of pimeloyl-CoA. The bio operon was not required for symbiosis, as only mutants in the nifA gene were impaired in symbiosis, and a bioA ::Tn 5 mutant was not impaired in rhizosphere colonization. The rationale for the vitamin biosynthetic loci being located on an acquired genetic element that is absent from nonsymbiotic mesorhizobia remains to be determined. Keywords: biotin biosynthesis, ß-ketoacyl-acyl carrier protein synthase III, horizontal gene transfer Abbreviations: NMN, nicotinic acid mononucleotide The GenBank accession number for the sequence reported in this paper is AF311738 .