A new synthesis method for complex electric field patterning using a multichannel dense array system with applications in low-intensity noninvasive neuromodulation.

Multichannel coil array systems offer precise spatiotemporal electronic steering and patterning of electric and magnetic fields without the physical movement of coils or magnets. This capability could potentially benefit a wide range of biomagnetic applications such as low-intensity noninvasive neuromodulation or magnetic drug delivery. In this regard, the objective of this work is to develop a unique synthesis method, that enabled by a multichannel dense array system, generates complex current pattern distributions not previously reported in the literature. Simulations and experimental results verify that highly curved or irregular (e.g., zig-zag) patterns at singular and multiple sites can be efficiently formed using this method. The synthesis method is composed of three primary components; a pixel cell (basic unit of pattern formation), a template array ("virtual array": code that disseminates the coil current weights to the "physical" dense array), and a hexagonal coordinate system. Low-intensity or low-field magnetic stimulation is identified as a potential application that could benefit from this work in the future and as such is used as an example to frame the research.

Comparative Hydrophobic Core Dynamics Between Wild-Type Amyloid-ß Fibrils, Glutamate-3 Truncation, and Serine-8 Phosphorylation.

Post-translational modifications (PTMs) of amyloid-ß (Aß) species are implicated in the modulation of overall toxicities and aggregation propensities. We investigated the internal dynamics in the hydrophobic core of the truncated ΔE3 mutant fibrils of Aß1-40 and compared them with prior and new data for wild-type fibrils as well as with phosphorylated S8 fibrils. Deuteron static solid-state NMR techniques, spanning line-shape analysis, longitudinal relaxation, and chemical exchange saturation transfer methods, were employed to assess the rotameric jumps of several methyl-bearing and aromatic groups in the core of the fibrils. Taken together, the results indicate the rather significant influence of the PTMs on the hydrophobic core dynamics, which propagates far beyond the local site of the chemical modification. The phosphorylated S8 fibrils display an overall rigidifying of the core based on the higher activation barriers of motions than the wild-type fibrils, whereas the ΔE3 fibrils induce a broader variety of changes, some of which are thermodynamic in nature rather than the kinetic ones.

Transradial interventions in contemporary vascular surgery practice.

OBJECTIVES: Upper extremity arterial access is often required for endovascular procedures, especially for antegrade access to the visceral aortic branches. Radial arterial access has been shown previously to have low complication rates, and patients tolerate the procedure well and are able to recover quickly. However, transradial access remains relatively uncommon amongst vascular surgeons. METHODS: The radial artery was evaluated by ultrasound to evaluate for adequate caliber, and to identify any aberrant anatomy or arterial loops. A modified Barbeau test was performed to ensure sufficient collateral circulation. A cocktail of nitroglycerin, verapamil and heparin was administered intra-arterially to combat vasospasm. Sheaths up to 6 French were utilized for interventions. On completion of the procedure, a compression band was used for hemostasis in all cases. RESULTS: Twenty-five interventions were performed in 24 patients. The left radial artery was used in 23/25 cases (92.0%). Procedures included visceral and renal artery interventions; stent graft repair of a renal artery aneurysm; embolization of splenic, pancreaticoduodenal and internal mammary aneurysms; embolization of bilateral hypogastric arteries following blunt pelvic trauma; interventions for peripheral arterial disease; delivery of a renal snorkel graft during endovascular aortic aneurysm repair, and access for diagnostic catheters during thoracic endovascular aortic aneurysm repair. Technical success was 92.0%. There was one post-operative radial artery occlusion (4.3%) which led to paresthesias but resolved with anticoagulation. There were no instances of arterial rupture, hematoma, or hand ischemia requiring intervention. CONCLUSIONS: Using the transradial approach, we have demonstrated a high technical success rate over a range of clinical contexts with minimal morbidity and no significant complications such as bleeding or hand ischemia. The safety profile compares favorably to historical complication rates from brachial access. Radial access is a safe and useful skill for vascular surgeons to master.

Interleukin receptor activates a MYD88-ARNO-ARF6 cascade to disrupt vascular stability.

The innate immune response is essential for combating infectious disease. Macrophages and other cells respond to infection by releasing cytokines, such as interleukin-1ß (IL-1ß), which in turn activate a well-described, myeloid-differentiation factor 88 (MYD88)-mediated, nuclear factor-κB (NF-κB)-dependent transcriptional pathway that results in inflammatory-cell activation and recruitment. Endothelial cells, which usually serve as a barrier to the movement of inflammatory cells out of the blood and into tissue, are also critical mediators of the inflammatory response. Paradoxically, the cytokines vital to a successful immune defence also have disruptive effects on endothelial cell-cell interactions and can trigger degradation of barrier function and dissociation of tissue architecture. The mechanism of this barrier dissolution and its relationship to the canonical NF-κB pathway remain poorly defined. Here we show that the direct, immediate and disruptive effects of IL-1ß on endothelial stability in a human in vitro cell model are NF-κB independent and are instead the result of signalling through the small GTPase ADP-ribosylation factor 6 (ARF6) and its activator ARF nucleotide binding site opener (ARNO; also known as CYTH2). Moreover, we show that ARNO binds directly to the adaptor protein MYD88, and thus propose MYD88-ARNO-ARF6 as a proximal IL-1ß signalling pathway distinct from that mediated by NF-κB. Finally, we show that SecinH3, an inhibitor of ARF guanine nucleotide-exchange factors such as ARNO, enhances vascular stability and significantly improves outcomes in animal models of inflammatory arthritis and acute inflammation.

Path to Impact for Autonomous Field Deployable Chemical Sensors: A Case Study of in Situ Nitrite Sensors.

Natural freshwater systems have been severely affected by excess loading of macronutrients (e.g., nitrogen and phosphorus) from fertilizers, fossil fuels, and human and livestock waste. In the USA, impacts to drinking water quality, biogeochemical cycles, and aquatic ecosystems are estimated to cost US$210 billion annually. Field-deployable nutrient sensors (FDS) offer potential to support research and resource management efforts by acquiring higher resolution data than are currently supported by expensive conventional sampling methods. Following nearly 40 years of research and development, FDS instruments are now starting to penetrate commercial markets. However, instrument uncertainty factors (high cost, reliability, accuracy, and precision) are key drivers impeding the uptake of FDS by the majority of users. Using nitrite sensors as a case study, we review the trends, opportunities, and challenges in producing and implementing FDS from a perspective of innovation and impact. We characterize the user community and consumer needs, identify trends in research approaches, tabulate state-of-the-art examples and specifications, and discuss data life cycle considerations. With further development of FDS through prototyping and testing in real-world applications, these tools can deliver information for protecting and restoring natural waters, enhancing process control for industrial operations and water treatment, and providing novel research insights.

Integration of genetic and physical maps of the Primula vulgaris S locus and localization by chromosome in situ hybridization.

Heteromorphic flower development in Primula is controlled by the S locus. The S locus genes, which control anther position, pistil length and pollen size in pin and thrum flowers, have not yet been characterized. We have integrated S-linked genes, marker sequences and mutant phenotypes to create a map of the P. vulgaris S locus region that will facilitate the identification of key S locus genes. We have generated, sequenced and annotated BAC sequences spanning the S locus, and identified its chromosomal location. We have employed a combination of classical genetics and three-point crosses with molecular genetic analysis of recombinants to generate the map. We have characterized this region by Illumina sequencing and bioinformatic analysis, together with chromosome in situ hybridization. We present an integrated genetic and physical map across the P. vulgaris S locus flanked by phenotypic and DNA sequence markers. BAC contigs encompass a 1.5-Mb genomic region with 1 Mb of sequence containing 82 S-linked genes anchored to overlapping BACs. The S locus is located close to the centromere of the largest metacentric chromosome pair. These data will facilitate the identification of the genes that orchestrate heterostyly in Primula and enable evolutionary analyses of the S locus.

A marine heatwave drives significant shifts in pelagic microbiology.

Marine heatwaves (MHWs) cause disruption to marine ecosystems, deleteriously impacting macroflora and fauna. However, effects on microorganisms are relatively unknown despite ocean temperature being a major determinant of assemblage structure. Using data from thousands of Southern Hemisphere samples, we reveal that during an "unprecedented" 2015/16 Tasman Sea MHW, temperatures approached or surpassed the upper thermal boundary of many endemic taxa. Temperate microbial assemblages underwent a profound transition to niche states aligned with sites over 1000 km equatorward, adapting to higher temperatures and lower nutrient conditions bought on by the MHW. MHW conditions also modulate seasonal patterns of microbial diversity and support novel assemblage compositions. The most significant affects of MHWs on microbial assemblages occurred during warmer months, when temperatures exceeded the upper climatological bounds. Trends in microbial response across several MHWs in different locations suggest these are emergent properties of temperate ocean warming, which may facilitate monitoring, prediction and adaptation efforts.

The E3 ubiquitin ligase CHIP and the molecular chaperone Hsc70 form a dynamic, tethered complex.

The E3 ubiquitin ligase CHIP (C-terminus of Hsc70 Interacting Protein, a 70 kDa homodimer) binds to the molecular chaperone Hsc70 (a 70 kDa monomer), and this complex is important in both the ubiquitination of Hsc70 and the turnover of Hsc70-bound clients. Here we used NMR spectroscopy, biolayer interferometry, and fluorescence polarization to characterize the Hsc70-CHIP interaction. We found that CHIP binds tightly to two molecules of Hsc70 forming a 210 kDa complex, with a Kd of approximately 60 nM, and that the IEEVD motif at the C-terminus of Hsc70 (residues 642-646) is both necessary and sufficient for binding. Moreover, the same motif is required for CHIP-mediated ubiquitination of Hsc70 in vitro, highlighting its functional importance. Relaxation-based NMR experiments on the Hsc70-CHIP complex determined that the two partners move independently in solution, similar to "beads on a string". These results suggest that a dynamic C-terminal region of Hsc70 provides for flexibility between CHIP and the chaperone, allowing the ligase to "search" a large space and engage in productive interactions with a wide range of clients. In support of this suggestion, we find that deleting residues 623-641 of the C-terminal region, while retaining the IEEVD motif, caused a significant decrease in the efficiency of Hsc70 ubiquitination by CHIP.

Heterogeneous expression of the virulence-related adhesin Epa1 between individual cells and strains of the pathogen Candida glabrata.

We investigated the relevance of gene expression heterogeneity to virulence properties of a major fungal pathogen, Candida glabrata. The organism's key virulence-associated factors include glycosylphosphatidylinositol-anchored adhesins, encoded subtelomerically by the EPA gene family. Individual-cell analyses of expression revealed very striking heterogeneity for Epa1, an adhesin that mediates ∼95% of adherence to epithelial cells in vitro. The heterogeneity in Epa1 was markedly greater than that known for other yeast genes. Sorted cells expressing high or low levels of Epa1 exhibited high and low adherence to epithelial cells, indicating a link between gene expression noise and potential virulence. The phenotypes of sorted subpopulations reverted to mixed phenotypes within a few generations. Variation in single-cell Epa1 protein and mRNA levels was correlated, consistent with transcriptional regulation of heterogeneity. Sir-dependent transcriptional silencing was the primary mechanism driving heterogeneous Epa1 expression in C. glabrata BG2, but not in CBS138 (ATCC 2001). Inefficient silencing in the latter strain was not due to a difference in EPA1 sequence or (sub)telomere length and was overcome by ectopic SIR3 expression. Moreover, differences between strains in the silencing dependence of EPA1 expression were evident across a range of clinical isolates, with heterogeneity being the greatest in strains where EPA1 was subject to silencing. The study shows how heterogeneity can impact the virulence-related properties of C. glabrata cell populations, with potential implications for microbial pathogenesis more broadly.

Ordered assembly of heat shock proteins, Hsp26, Hsp70, Hsp90, and Hsp104, on expanded polyglutamine fragments revealed by chemical probes.

In Saccharomyces cerevisae, expanded polyglutamine (polyQ) fragments are assembled into discrete cytosolic aggregates in a process regulated by the molecular chaperones Hsp26, Hsp70, Hsp90, and Hsp104. To better understand how the different chaperones might cooperate during polyQ aggregation, we used sequential immunoprecipitations and mass spectrometry to identify proteins associated with either soluble (Q25) or aggregation-prone (Q103) fragments at both early and later times after induction of their expression. We found that Hsp26, Hsp70, Hsp90, and other chaperones interact with Q103, but not Q25, within the first 2 h. Further, Hsp70 and Hsp90 appear to be partially released from Q103 prior to the maturation of the aggregates and before the recruitment of Hsp104. To test the importance of this seemingly ordered process, we used a chemical probe to artificially enhance Hsp70 binding to Q103. This treatment retained both Hsp70 and Hsp90 on the polyQ fragment and, interestingly, limited subsequent exchange for Hsp26 and Hsp104, resulting in incomplete aggregation. Together, these results suggest that partial release of Hsp70 may be an essential step in the continued processing of expanded polyQ fragments in yeast.

Features of protein-protein interactions that translate into potent inhibitors: topology, surface area and affinity.

Protein-protein interactions (PPIs) control the assembly of multi-protein complexes and, thus, these contacts have enormous potential as drug targets. However, the field has produced a mix of both exciting success stories and frustrating challenges. Here, we review known examples and explore how the physical features of a PPI, such as its affinity, hotspots, off-rates, buried surface area and topology, might influence the chances of success in finding inhibitors. This analysis suggests that concise, tight binding PPIs are most amenable to inhibition. However, it is also clear that emerging technical methods are expanding the repertoire of 'druggable' protein contacts and increasing the odds against difficult targets. In particular, natural product-like compound libraries, high throughput screens specifically designed for PPIs and approaches that favour discovery of allosteric inhibitors appear to be attractive routes. The first group of PPI inhibitors has entered clinical trials, further motivating the need to understand the challenges and opportunities in pursuing these types of targets.

Stable fixation of short-stem femoral implants in patients 70 years and older.

BACKGROUND: Limitations of conventional uncemented femoral stems persist, including proximal-distal mismatch, nonideal load transfer, loss of bone, and difficulties with minimally invasive surgery. Metaphyseal-engaging short-stem implants have been designed to address these issues in THA. While these devices have been studied in younger patients, it is unclear whether they offer advantages in older patients. QUESTIONS/PURPOSES: We asked whether the stability and bony ingrowth of an off-the-shelf short stem in patients 70 years and older were similar to those achieved in patients younger than 70 years at 2-year followup. Furthermore, we asked whether pain and function scores were affected by age, bone quality, or varus alignment. PATIENTS AND METHODS: We retrospectively reviewed 60 patients (65 hips) 70 years and older (mean, 75 years; range, 70-86 years) treated with an uncemented short stem (range, 90-105 mm). We compared radiographic alignment, stability, and bony ingrowth, as well as Harris hip scores and WOMAC pain scores, to a cohort of 89 patients (91 hips) younger than 70 years. Minimum followup was 24 months (mean, 35 months; range, 24-60 months). RESULTS: Radiographs showed proximal bony ingrowth and stable fixation of all implants. Average Harris hip score at last followup was 88 (range, 70-100) for the 70 years and older cohort and 93 (range, 70-100) for younger than 70 years cohort; no patients reported thigh pain. Postoperative WOMAC scores averaged 6 (range, 0-43) and 5 (range, 0-25), respectively. CONCLUSIONS: Short-stem implants provide solid, dependable fixation in osteoporotic bone at minimum 2-year followup, while meeting some of the limitations in conventional primary THA. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Floral heteromorphy in Primula vulgaris: progress towards isolation and characterization of the S locus.

BACKGROUND: The common primrose, Primula vulgaris, along with many other species of the Primulaceae, exhibits floral heteromorphy in which different individuals develop one of two possible forms of flower, known as pin and thrum. Both flower types are hermaphrodite and exhibit reciprocal positions of male and female reproductive structures, which together with a sporophytic incompatibility system, prevent self-pollination and promote out-crossing. The development of the two different forms of flower is controlled by a co-adapted linkage group of genes known as the S locus. SCOPE: Here progress towards identification and characterization of these genes is described to provide a molecular genetic explanation of the different floral characteristics that define heterostyly in Primula as observed and described by Charles Darwin. Previous work to identify and characterize developmental mutations linked to the P. vulgaris S locus, together with the isolation of S locus-linked genes and polymorphic DNA sequences markers, is summarized. The development of tools are described which will facilitate isolation and characterization of the S locus and its environs, including the creation of two expressed sequence tag libraries from pin and thrum flowers, as well as the construction and screening of two bacterial artificial chromosome (BAC) libraries containing thrum genomic DNA. Screening of these libraries with four S locus-linked sequences has enabled us to assemble four BAC contigs representing over 40 individual overlapping BAC clones which represent over 2·2 Mb of S locus-linked genomic sequence. PCR-based approaches for identification of the allelic origin of these BACs are described as well as identification of an additional 14 S locus-linked genes within BAC-end sequences. CONCLUSIONS: On-going work to assemble the four S locus-linked contigs into one contiguous sequence spanning the S locus is outlined in preparation for sequence analysis and characterization of the genes located within this region.

Improved synthesis of 15-deoxyspergualin analogs using the Ugi multi-component reaction.

Spergualin is a natural product that exhibits immunosuppressive, anti-tumor and anti-bacterial activities. Its derivatives, such as 15-deoxyspergualin (15-DSG), have been clinically approved for acute allograft rejection. However, the reported syntheses are cumbersome (>10 steps) and they suffer from low overall yields (∼0.3% to 18%). Moreover, spergualin and its derivatives are chemically unstable and rapidly hydrolyzed in aqueous buffer. Here, we have re-explored these issues and report a modified synthetic route with significantly improved overall yield (∼31% to 47%). The key transformation is a microwave-accelerated Ugi multi-component reaction that is used to generate the peptoid core in a single step. Using the products of this route, we found that modifications of the hemiaminal significantly increased chemical stability. Thus, we anticipate that this synthetic route will improve access to biologically active 15-DSG derivatives.

Mechanisms of vascular stability and the relationship to human disease.

PURPOSE OF REVIEW: The genetic basis for a variety of vascular malformation syndromes have been described, with an increasing functional understanding of the associated genes. RECENT FINDINGS: Genes responsible for familial vascular malformation syndromes have increasingly been shown to be involved in the control of vascular stability. SUMMARY: Genes involved in vascular stability pathways are good candidates for causing vascular malformation syndromes. Although these findings confirm the biologic importance of the involved pathways, further explanations are required to describe the focal nature of disease.

A motif in the C-terminal domain of phiC31 integrase controls the directionality of recombination.

Bacteriophage C31 encodes an integrase, which acts on the phage and host attachment sites, attP and attB, to form an integrated prophage flanked by attL and attR. In the absence of accessory factors, C31 integrase cannot catalyse attL x attR recombination to excise the prophage. To understand the mechanism of directionality, mutant integrases were characterized that were active in excision. A hyperactive integrase, Int E449K, gained the ability to catalyse attL x attR, attL x attL and attR x attR recombination whilst retaining the ability to recombine attP x attB. A catalytically defective derivative of this mutant, Int S12A, E449K, could form stable complexes with attP/attB, attL/attR, attL/attL and attR/attR under conditions where Int S12A only complexed with attP/attB. Further analysis of the Int E449K-attL/attR synaptic events revealed a preference for one of the two predicted synapse structures with different orientations of the attL/attR sites. Several amino acid substitutions conferring hyperactivity, including E449K, were localized to one face of a predicted coiled-coil motif in the C-terminal domain. This work shows that a motif in the C-terminal domain of C31 integrase controls the formation of the synaptic interface in both integration and excision, possibly through a direct role in protein-protein interactions.

Does the (13)C of foliage-respired CO(2) and biochemical pools reflect the (13)C of recently assimilated carbon?

Isotopic labelling experiments were conducted to assess relationships among (13)C of recently assimilated carbon (deltaC(A)), foliage respiration (deltaC(F)), soluble carbohydrate (deltaC(SC)), leaf waxes (deltaC(LW)) and bulk organic matter (deltaC(OM)). Slash pine, sweetgum and maize were grown under (13)C depleted CO(2) to label biomass and then placed under ambient conditions to monitor the loss of label. In pine and sweetgum, deltaC(F) of labelled plants (approximately -44 and -35 per thousand, respectively) rapidly approached control values but remained depleted by approximately 4-6 per thousand after 3-4 months. For these tree species, no or minimal label was lost from deltaC(SC), deltaC(LW) and deltaC(OM) during the observation periods. deltaC(F) and deltaC(SC) of labelled maize plants rapidly changed and were indistinguishable from controls after 1 month, while deltaC(LW) and deltaC(OM) more slowly approached control values and remained depleted by 2-6 per thousand. Changes in deltaC(F) in slash pine and sweetgum fit a two-pool exponential model, with the fast turnover metabolic pool (approximately 3-4 d half-life) constituting only 1-2% of the total. In maize, change in deltaC(F) fits a single pool model with a half-life of 6.4 d. The (13)C of foliage respiration and biochemical pools reflect temporally integrated values of deltaC(A), with change in isotopic composition dampened by the size of metabolic carbon reserves and turnover rates.

Component Microenvironments and System Biogeography Structure Microorganism Distributions in Recirculating Aquaculture and Aquaponic Systems.

Flowthrough and pond aquaculture system microbiome management practices aim to mitigate fish disease and stress. However, the operational success of recirculating aquaculture systems (RAS) depends directly on system microbial community activities. In RAS, each component environment is engineered for a specific microbial niche for waste management, as the water continuously flowing through the system must be processed before returning to the rearing tank. In this study, we compared waste management component microbiomes (rearing tank water, pH correction tank, solid-waste clarifier, biofilter, and degassing tower) within a commercial-scale freshwater RAS by high-throughput 16S rRNA gene sequencing. To assess consistency among freshwater RAS microbiomes, we also compared the microbial community compositions of six aquaculture and aquaponic farms. Community assemblages reflected site and source water relationships, and the presence of a hydroponic subsystem was a major community determinant. In contrast to the facility-specific community composition, some sequence variants, mainly classified into Flavobacterium, Cetobacterium, the family Sphingomonadaceae, and nitrifying guilds of ammonia-oxidizing archaea and Nitrospira, were common across all facilities. The findings of this study suggest that, independently of system design, core taxa exist across RAS rearing similar fish species but that system design informs the individual aquatic microbiome assemblages. Future RAS design would benefit from understanding the roles of these core taxa and then capitalizing on their activities to further reduce system waste/added operational controls.IMPORTANCE Recirculating aquaculture systems (RAS) are agroecosystems for intensive on-land cultivation of products of fisheries. Practitioners that incorporate edible plant production into RAS refer to these facilities as aquaponic systems (AP). RAS have the potential to offset declining production levels of wild global fisheries while reducing waste and product distance to market, but system optimization is needed to reduce costs. Both RAS and AP rely on microbial consortia for maintaining water quality and promoting fish/plant health, but little is known about the microorganisms actually present. This lack of knowledge prevents optimization of designs and operational controls to target the growth of beneficial microbial species or consortia. The significance of our research is in identifying the common microorganisms that inhabit production RAS and AP and the operational factors that influence which microorganisms colonize and become abundant. Identifying these organisms is a first step toward advanced control of microbial activities that improve reproducibility and reduce costs.

Seizures following picornavirus infection.

PURPOSE: We demonstrate the establishment and characterization of a novel virus infection-induced seizure model in C57BL/6 mice. METHODS: C57BL/6 mice were infected with Theiler's murine encephalomyelitis virus (TMEV) or mock infected. Mice were followed for seizures, weight change, body temperature, motor function (righting reflex, rotorod) and neurological manifestations (inflammation [perivascular cuffing], pyknotic neurons, transforming growth factor [TGF]-beta expression). RESULTS: C57BL/6 mice are susceptible to seizures induced by TMEV infection. Approximately 50% of C57BL/6 mice develop transient afebrile seizures. Motor function and coordination are impaired in seized mice. Pyramidal neuron pyknosis and TGF-beta expression correlate with seizure activity in the hippocampus. DISCUSSION: The characterization of this model will enable the investigation of viral and immune contributions in the central nervous system to the development of seizure disorders in humans.

Natural and synthetic tetracycline-inducible promoters for use in the antibiotic-producing bacteria Streptomyces.

Bacteria in the genus Streptomyces are major producers of antibiotics and other pharmacologically active compounds. Genetic and physiological manipulations of these bacteria are important for new drug discovery and production development. An essential part of any 'genetic toolkit' is the availability of regulatable promoters. We have adapted the tetracycline (Tc) repressor/operator (TetR/tetO) regulatable system from transposon Tn10 for use in Streptomyces. The synthetic Tc controllable promoter (tcp), tcp830, was active in a wide range of Streptomyces species, and varying levels of induction were observed after the addition of 1-100 ng/ml of anhydrotetracycline (aTc). Streptomyces coelicolor contained an innate Tc-controllable promoter regulated by a TetR homologue (SCO0253). Both natural and synthetic promoters were active and inducible throughout growth. Using the luxAB genes expressing luciferase as a reporter system, we showed that induction factors of up to 270 could be obtained for tcp830. The effect of inducers on the growth of S.coelicolor was determined; addition of aTc at concentrations where induction is optimal, i.e. 0.1-1 microg/ml, ranged from no effect on growth rate to a small increase in the lag period compared with cultures with no inducer.