Screening system for xenosiderophores as potential drug delivery agents inmycobacteria

Citation
G. Schumann et U. Mollmann, Screening system for xenosiderophores as potential drug delivery agents inmycobacteria, ANTIM AG CH, 45(5), 2001, pp. 1317-1322
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
ISSN journal
0066-4804 → ACNP
Volume
45
Issue
5
Year of publication
2001
Pages
1317 - 1322
Database
ISI
SICI code
0066-4804(200105)45:5<1317:SSFXAP>2.0.ZU;2-X
Abstract
In order to establish a screening system for xenosiderophores which can be utilized by mycobacteria, we generated a set of mutants of Mycobacterium sm egmatis that are blocked in different steps of the well-known iron acquisit ion system. One mutant with a block in mycobactin biosynthesis was generate d from strain mc(2)155 by chemical mutagenesis, The exochelin biosynthesis gene fxbA and the ferric exochelin uptake gene fxuA, previously identified by Fiss et al, (E, H, Fiss, S, Yu, and W, R, Jacobs, Jr,, Mel. Microbiol, 1 4:557-559, 1994), were knocked out by gene replacement. Adjacent chromosoma l fragments were used for homologous recombination in order to replace wild -type genes by the kanamycin resistance gene from transposon Tn903, Gene re placement was confirmed by PCR, The isolated mutants show the expected phen otype: fxbA mutants are defective in exochelin biosynthesis, whereas fxuA m utants excrete a significantly larger amount of exochelin compared to the a mount excreted by the parent strain, This is due to their defectiveness in ferriexochelin uptake, as demonstrated in growth promotion assays. This new set of mutants allows differentiation of siderophores that supply mycobact eria with iron by ligand exchange with exochelin or mycobactin, by the use of separate siderophore uptake routes, or by the use of the exochelin perme ase, All these types of iron uptake routes were identified with 25 exogenou s siderophores as test substances. Siderophores that act without ligand exc hange are potential candidates as drug vectors that can be used to overcome permeability-mediated resistance.