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A new Escherichia coli host/vector system has been engineered to allow tight and uniform modulation of gene expression and gamma origin (ori) plasmid copy number. Regulation of gamma ori plasmid copy number is achieved through arabinose-inducible expression of the necessary Rep protein, pi, whose gene was integrated into the chromosome of the host strain(More)
The introduction or creation of metabolic pathways in microbial hosts has allowed for the production of complex chemicals of therapeutic and industrial importance. However, these pathways rarely function optimally when first introduced into the host organism and can often deleteriously affect host growth, resulting in suboptimal yields of the desired(More)
A small-volume sentinel chamber was developed to assess the effects of environmental stresses on survival of sucrose-Percoll-purified Cryptosporidium parvum oocysts in soil and animal wastes. Chambers were tested for their ability to equilibrate with external chemical and moisture conditions. Sentinel oocysts were then exposed to stresses of the external(More)
BACKGROUND Artemisinin derivatives are the key active ingredients in Artemisinin combination therapies (ACTs), the most effective therapies available for treatment of malaria. Because the raw material is extracted from plants with long growing seasons, artemisinin is often in short supply, and fermentation would be an attractive alternative production(More)
Rhodobacter sphaeroides rpoE encodes a 19.2 kDa protein, sigma(E), related to members of the extra-cytoplasmic function subfamily of eubacterial RNA polymerase sigma factors. We demonstrate that sigma(E) directs transcription from rpoE P1, the promoter for the rpoEchrR operon, and from cycA P3, a promoter for the cytochrome c2 structural gene. Comparison of(More)
It is clear that multiple sites of interaction exist between sigmas and core subunits, likely reflecting the changing pattern of interactions that occur sequentially during the complex process of holoenzyme formation, open promoter formation, and initiation of transcription. Recent studies have revealed that a major site of interaction of Escherichia coli(More)
Prokaryotic RNA polymerase holoenzyme is composed of core subunits (alpha(2)betabeta'omega) plus a sigma factor that confers promoter specificity allowing for regulation of gene expression. Holoenzyme is known to undergo several conformational changes during the multiple steps of transcription initiation. However, the effects of these changes on the(More)
The structure and composition of the oocyst wall are primary factors determining the survival and hydrologic transport of Cryptosporidium parvum oocysts outside the host. Microscopic and biochemical analyses of whole oocysts and purified oocyst walls were undertaken to better understand the inactivation kinetics and hydrologic transport of oocysts in(More)
A series of low-copy expression vectors that permits the stable maintenance and regulated expression of highly toxic gene products has been developed. These vectors utilize the lactose promoter/operator system, and protect against read-through transcription from other promoters on the plasmid by placement of the rrnB T1T2 terminators upstream of the lactose(More)
Adaptation of bacterial cells to diverse habitats relies on the ability of RNA polymerase to respond to various regulatory signals. Some of these signals are conserved throughout evolution, whereas others are species specific. In this study we present a comprehensive comparative analysis of RNA polymerases from two distantly related bacterial species,(More)