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Transcriptional regulation of the growth phase regulated porin, OpnS in the mutualistic bacterium, Xenorhabdus nematophila
Author(s) -
Hoeven Ransome,
Forst Steven
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.782.31
Subject(s) - biology , repressor , transcription (linguistics) , regulon , transcription factor , bacterial outer membrane , mutant , effector , genetics , porin , microbiology and biotechnology , gene , escherichia coli , linguistics , philosophy
Porins are small water filled channels that allow nutrients to diffuse across the outer membrane of Gram negative bacteria. The goal of this study was to characterize the transcriptional regulation of a novel porin, OpnS, in Xenorhabdus nematophila . RT‐PCR and urea SDS‐PAGE analysis of outer membrane proteins revealed that opnS mRNA and OpnS protein were expressed predominantly as cells transitioned into stationary phase. The EnvZ‐OmpR two‐component signal transduction system was shown to control the transcription of opnS . Expression of opnS mRNA as well as OpnS protein levels were reduced in both mutant strains. To quantify the level of transcription, a opnS‐lacZ fusion was constructed and β‐galactosidase activity was measured in wild type, ompR − and envZ − strains. β‐gal activity was reduced by 50% and 20% in the ompR − and envZ − mutants respectively. A 2‐fold increase in β–gal activity was observed in a strain in which var1 , encoding a putative global regulator of transcription, was inactivated. 5′ RACE studies of the upstream region of the opnS gene revealed the presence of two transcription start sites suggesting the existence of two sigma 70 promoters. Further, promoter deletions using opnS‐lacZ fusions identified putative repressor and activation sites to both promoters 1 and 2 of the regulatory region. Understanding the regulation and function of OpnS in the life cycle of X. nematophila are in progress.