Experiments requiring strong repression and precise control of cloned genes can be difficult to conduct because of the relatively high basal level of expression of currently employed promoters. We report the construction of a family of vectors that contain a reengineered lacIq-lac promoter-operator complex in which cloned genes are strongly repressed in the absence of inducer. The vectors, all based on the broad-host-range plasmid pBBR1, are mobilizable and stably replicate at moderate copy number in representatives of the alpha- and gammaproteobacteria. Each vector contains a versatile multiple cloning site that includes an NdeI site allowing fusion of the cloned gene to the initiation codon of lacZ. In each tested bacterium, a uidA reporter fused to the promoter was not expressed at a detectable level in the absence of induction but was inducible by 10- to 100-fold, depending on the bacterium. The degree of induction was controllable by varying the concentration of inducer. When the vector was tested in Agrobacterium tumefaciens, a cloned copy of the traR gene, the product of which is needed at only a few copies per cell, did not confer activity under noninducing conditions. We used this attribute of very tight and variably regulatable control to assess the relative amounts of TraR required to activate the Ti plasmid conjugative transfer system. We identified levels of induction that gave wild-type transfer frequencies, as well as levels that induced correspondingly lower frequencies of transfer. We also used this system to show that the antiactivator TraM sets the level of intracellular TraR required for tra gene activation.
- American Society for Microbiology
- Broad-host-range expression vectors with tightly regulated ...
3 Water Utilities that Lowered their Arsenic Levels with AdEdge
Finding an appropriate solution to address arsenic in raw water can be challenging for utilities. Studies have shown that when ingested in high concentrations, it is linked to cancer in the skin, lungs, bladder and kidney, and can cause significant skin changes, such as thickening and pigmentation, as well as other health issues. For this reason, the U.S. Environmental Protection Agency (EPA) has a maximum contaminant level standard of 0.01 mg/L. Throughout the country, municipalities are looking for ways to...
The first monitoring well in Engbertsdijksvenen is a reality
On Wednesday 20 December 2017, the first monitoring well of the groundwater monitoring network Engbertsdijksvenen was realised on the parcel of landowner Wilharms in Vriezenveen. This monitoring well serves to monitor the effects of the measures required for the Nature Objectives of the Engbertsdijksveen. One of these goals is the recovery of living high moor. In addition to this monitoring well, Eijkelkamp Soil & Water will also install 58 other monitoring wells within a radius of approximately 1.5 kilometres...
On-Line Fast Analysis of AMC from ppt to % levels in Clean Air Room
To ensure people’s safety and a good repeatability of industrial process, near real-time risk management and the continuous monitoring are crucial. In the semiconductor fabrication process, particle control is an essential part. Clean room technology, which relies on the use of HEPA and ULPA filtration, has in the past exclusively focused on the control of micro- and nano-particles. Nevertheless, as a consequence of device reduction, Airborne Molecular Contaminations (AMCs) has also become a key detractor...
Living near a fracking well means more asthma attacks
It`s probably telling that the word ‘fracking’ sounds just shy of a curse word. Researchers at the Johns Hopkins Bloomberg School of Public Health have found that people who live near active, unconventional natural gas wells operated by the fracking industry were significantly more likely to suffer from asthma attacks. It’s the latest in a string of studies that has linked the fracking industry to health issues including lower birth weights, skin problems and upper respiratory issues. First...
Area monitoring of specific ppb-level constituents utilizing process gas chromatography
ABSTRACTIn most of the industrialized countries worldwide, increasingly stringent environmental regulations require the continuous reduction of a wide range of emission sources and components. Despite local variations concerning concentrations, absolute emission quantity, target priorities and timetables, regulations typically require active compliance and proof thereof. The impact of more stringent regulation requires, in addition to point source, frequent area monitoring of target constituents. Whereas point...