HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (Papers in Press[PDF]) All Versions of this Article: mic.0.028688-0v1 155/6/1866    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Ganas, P. Articles by Brandsch, R. Search for Related Content PubMed PubMed Citation Articles by Ganas, P. Articles by Brandsch, R. Agricola Articles by Ganas, P. Articles by Brandsch, R.

Uptake of L-nicotine and of 6-hydroxy-L-nicotine by Arthrobacter nicotinovorans and by Escherichia coli is mediated by facilitated diffusion and not by passive diffusion or active transport

¹ Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research;
² Universität Freiburg

ABSTRACT

The mechanism by which L-nicotine is taken up by bacteria that are able to grow on it is unknown. Nicotine degradation by Arthrobacter nicotinovorans, a Gram + soil bacterium, is linked to the presence of the catabolic megaplasmid pAO1. [14C]-L-nicotine uptake assays with A. nicotinovorans showed transport of nicotine across the cell membrane to be energy independent and saturable with a Km of 6.2 ± 0.1 µM and a Vmax of 0.70 ± 0.08 µmol min-1 mg-1 protein. This is in accord with a mechanism of facilitated diffusion, driven by the nicotine concentration gradient. Nicotine uptake was coupled to its intracellular degradation and an A. nicotinovorans strain unable to degrade nicotine (pAO1-) showed no nicotine import. However, when the nicotine dehydrogenase genes were expressed in this strain import of [14C]-L-nicotine took place. A. nicotinovorans pAO1- and Escherichia coli were also unable to import 6-hydroxy-L-nicotine, but expression of the 6-hydroxy-L-nicotine oxidase gene allowed both bacteria to take up this compound. L-nicotine uptake was inhibited by D-nicotine, 6-hydroxy-L-nicotine and 2-amino-L-nicotine which may indicate transport of these nicotine derivatives by a common permease. Attempts to correlate nicotine uptake with pAO1 genes with similarity to amino acid transporters failed. In contrast to the situation at the blood-brain barrier nicotine transport across the cell membrane by these bacteria was not by passive diffusion or active transport but by facilitated diffusion.

³ E-mail: roderich.brandsch{at}biochemie.uni-freiburg.de