A Genomic View of Sugar Transport in Mycobacterium smegmatis and Mycobacterium tuberculosis

Lehrstuhl für Mikrobiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 5, D-91058 Erlangen, Germany, Department of Microbiology, University of Alabama at Birmingham, 613 Bevill Biomedical Research Building, 845 19th Street South, Birmingham, AL 35294, U.S.A.

^* To whom correspondence should be addressed. Email: fritz.titgemeyer{at}googlemail.com. mnieder{at}uab.edu.

	Abstract

We present a comprehensive analysis of carbohydrate uptake systems of the soil bacterium Mycobacterium smegmatis and the human pathogen Mycobacterium tuberculosis. Our results show that M. smegmatis has 28 putative carbohydrate transporters. The majority of sugar transport systems (19/28) in M. smegmatis belongs to the ATP-binding cassette (ABC) transporter family. In contrast to previous reports, we identified in M. smegmatis genes encoding all components of the phosphotransferase system (PTS) including permeases for fructose, glucose, and dihydroxyacetone. It is anticipated that the PTS of M. smegmatis plays an important role in the global control of carbon metabolism similar as in other bacteria. M. smegmatis further possesses one putative glycerol facilitator of the major intrinsic protein (MIP) family, four sugar permeases of the major facilitator super family (MFS) of which one was assigned as a glucose transporter, and one galactose permease of the sodium solute super family (SSS). Our predictions were validated by gene expression, growth and sugar transport analyses. Strikingly, we detected only five sugar permeases in the slow-growing M. tuberculosis, of which two occur in M. smegmatis. Genes for a PTS are missing in M. tuberculosis. Our analysis brings thus the diversity of carbohydrate uptake systems between a fast- and a slow-growing mycobacterium to light, which reflects the lifestyles of M. smegmatis and M. tuberculosis in their natural habitats, the soil and the human body.