ISSN:
1617-4623
Keywords:
Key wordsβ-Glucoside
;
Azospirillum irakense
;
Transcriptional repressor
;
LacI
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The salAB genes of Azospirillum irakense KBC1, which encode two aryl-β-glucosidases, are required for growth on salicin. In the 4-kb region upstream of the salAB genes, two additional genes, salC and salR, were identified. SalC shows characteristics of the outer membrane receptors in the FepA/FhuA family. The salCAB genes are transcribed as a polycistronic mRNA. The salR gene encodes a protein homologous to the LacI/GalR family of transcriptional repressors. Expression of the sal operon, measured by means of a salC-gusA translational fusion in A. irakense KBC1, requires the presence of aryl-β-glucosides such as arbutin and salicin. Expression is markedly enhanced when a simple carbon source, like glucose, cellobiose or malate, is added to the medium. In a salR mutant, expression of the salC-gusA fusion does not require an aryl-β-glucoside inducer. Expression of a salR-gusA fusion is constitutive. The product of arbutin hydrolysis (hydroquinone) partly inhibits the expression of a salC-gusA fusion in arbutin- or salicin-containing minimal medium. This effect is independent of SalR. Salicylalcohol, the hydrolysis product of salicin, also partly inhibits salC expression in a SalR-independent fashion, but only in salicin-containing minimal medium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00008692
