RESEARCH ARTICLE Open Access Characterization of the biotin uptake system encoded by the biotin-inducible bioYMN operon of Corynebacterium glutamicum Jens Schneider 1 , Petra Peters-Wendisch 1,3* , K Corinna Stansen 1 , Susanne Götker 1 , Stanislav Maximow 2 , Reinhard Krämer 2 and Volker F Wendisch 1 Abstract Background: The amino acid-producing Gram-positive Corynebacterium glutamicum is auxotrophic for biotin although biotin ring assembly starting from the precursor pimeloyl-CoA is still functional. It possesses AccBC, the a- subunit of the acyl-carboxylases involved in fatty acid and mycolic acid synthesis, and pyruvate carboxylase as the only biotin-containing proteins. Comparative genome analyses suggested that the putative transport system BioYMN encoded by cg2147, cg2148 and cg2149 might be involved in biotin uptake by C. glutamicum. Results: By comparison of global gene expression patterns of cells grown with limiting or excess supply of biotin or with dethiobiotin as supplement replacing biotin revealed that expression of genes coding for enzymes of biotin ring assembly and for the putative uptake system was regulated according to biotin availability. RT-PCR and 5’-RACE experiments demonstrated that the genes bioY, bioM, and bioN are transcribed from one promoter as a single transcript. Biochemical analyses revealed that BioYMN catalyzes the effective uptake of biotin with a concentration of 60 nM biotin supporting a half-maximal transport rate. Maximal biotin uptake rates were at least five fold higher in biotin-limited cells as compared to cells grown with excess biotin. Overexpression of bioYMN led to an at least 50 fold higher biotin uptake rate as compared to the empty vector control. Overproduction of BioYMN alleviated biotin limitation and interfered with triggering L-glutamate production by biotin limitation. Conclusions: The operon bioYMN from C. glutamicum was shown to be induced by biotin limitation. Transport assays with radio-labeled biotin revealed that BioYMN functions as a biotin uptake system. Overexpression of bioYMN affected L-glutamate production triggered by biotin limitation. Background Biotin is a vitamin in humans (vitamin H or B7). Biotin deficiency is rarely observed in humans, e.g. after pro- longed consumption of raw egg whites that contains biotin-binding avidin [1], as the normal microflora of the large intestine is considered to provide sufficient supply of biotin. If biotin is lacking, multiple carboxylase deficiencies arise [1] because biotin is a cofactor of the biotin-dependent carboxylases, which occur in all domains of life [2]. Many bacteria can synthesize biotin, but biotin auxotrophic bacteria such as Corynebacterium glutamicum require uptake of biotin from the habitat. Biotin synthesis can be subdivided into synthesis of pimelic acid followed by the biotin ring assembly [3]. Biotin ring assembly occurs via the well-studied enzymes 8-amino-7-oxononanoate synthase, 7,8-diami- nononanoate synthase, dethiobiotin synthase and biotin synthase encoded by bioF, bioA, bioD and bioB, respec- tively [2]. Pimelate synthesis occurs via two alternative routes as found in Bacillus subtilis and Escherichia coli, respectively [3]. In B. subtilis, pimeloyl-CoA is generated by interception of fatty acid biosynthesis by P450-depen- dent BioI, which yields pimeloyl-ACP chains by oxida- tive cleavage of long-chain acyl-ACPs [4]. In E. coli , malonyl-CoA methyl ester is generated by SAM-depen- dent methyltransferase BioC as a primer molecule and afterwards elongated in fatty acid biosynthesis to yield methyl-pimeloyl-ACP which finally is demethylated by * Correspondence: petra.peters-wendisch@uni-bielefeld.de 1 Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany Full list of author information is available at the end of the article Schneider et al. BMC Microbiology 2012, 12:6 http://www.biomedcentral.com/1471-2180/12/6 © 2012 Schneider et al; licensee BioMed Central Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.