Expression of horizontally transferred gene clusters: activation by promoter-generating mutations

Citation
S. Dabizzi et al., Expression of horizontally transferred gene clusters: activation by promoter-generating mutations, RES MICROB, 152(6), 2001, pp. 539-549
Citations number
32
Categorie Soggetti
Microbiology
Journal title
RESEARCH IN MICROBIOLOGY
ISSN journal
09232508 → ACNP
Volume
152
Issue
6
Year of publication
2001
Pages
539 - 549
Database
ISI
SICI code
0923-2508(200107/08)152:6<539:EOHTGC>2.0.ZU;2-L
Abstract
The occurrence of promoter-generating mutations allowing the transcription of heterologous genes has been studied in a system based on the plasmid-med iated conjugal transfer of histidine biosynthetic genes from a donor bacter ium (Azospirillum brasilense) into a heterologous Escherichia coli mutant p opulation lacking histidine biosynthetic ability and initially unable to re cognize the transcriptional signal of the introgressed. gene(s). Under sele ctive stressful conditions, His(+) revertants accumulated in the E. coli Hi s(-) culture. The number of His(+) colonies was dependent on the time of in cubation under selective conditions, the strength of selective pressure, an d on the crowding of cells plated; moreover, it was independent of the phys iological status of the cell (i.e. the growth phase). Sequence analysis of plasmid DNA extracted from E. coli His(+) revertants revealed that single b ase substitutions in the region upstream of the A. brasilense his operon. r esulted in an adjustment of the pre-existing sequence that was rendered sim ilar to the E. coli - 10 promoter sequence and transcriptable by the host R NA-polymerase. One particular transition (C --> T) was predominant in the H is(+) revertants. Data presented here indicated that the barriers to the ex pression of horizontally transferred heterologous genes or operons may be o vercome in a short time scale and at high frequency, and supported the self ish operon model on the origin and evolution of gene clusters. (C) 2001 Edi tions scientifiques et medicales Elsevier SAS.