A homologue of the tryptophan-rich sensory protein TspO and FixL regulate a novel nutrient deprivation-induced Sinorhizobium meliloti locus

Citation
Me. Davey et Fj. De Bruijn, A homologue of the tryptophan-rich sensory protein TspO and FixL regulate a novel nutrient deprivation-induced Sinorhizobium meliloti locus, APPL ENVIR, 66(12), 2000, pp. 5353-5359
Citations number
59
Categorie Soggetti
Biology,Microbiology
Journal title
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
ISSN journal
00992240 → ACNP
Volume
66
Issue
12
Year of publication
2000
Pages
5353 - 5359
Database
ISI
SICI code
0099-2240(200012)66:12<5353:AHOTTS>2.0.ZU;2-G
Abstract
A nutrient deprivation-induced locus in Sinorhizobium meliloti strain 1021 was identified by use of a Tn5-luxAB reporter gene transposon, The tagged l ocus is comprised of two open reading frames (ORFs) designated ndiA and ndi B for nutrient deprivation-induced genes A and B. Comparison of the deduced amino acid sequences of both ndiA and ndiB to the protein databases failed to reveal similarity to any known genes. The expression of the ndi locus w as found to be induced by carbon and nitrogen deprivation, osmotic stress, and oxygen limitation and during entry into stationary phase. To identify r egulatory components involved in the control of ndi gene expression, a seco nd round of mutagenesis was performed on the primary ndiB::Tn5-lunAB-tagged strain (C22) with transposon Tn1721, A double-mutant strain was obtained t hat lacked ndi locus transcriptional activity under ail of the inducing con ditions tested. The Tn1721-tagged gene showed a high degree of similarity t o tryptophan-rich sensory protein TspO from Rhodobacter sphaeroides, as wel l as to mitochondrial benzodiazepine receptor pK18 from mammals. Induction of the ndi::Tn5-luxAB reporter gene fusion was restored under all inducing conditions by introducing the tspO coding region, from either S, meliloti o r R sphaeroides, in trans. Furthermore, it was found that, in addition to t spO,fixL, which encodes the sensor protein of an oxygen-sensing two-compone nt system, is required for full expression of the ndi locus, but only under low oxygen tension.