Fluorescent Sensor Arrays Can Predict and Quantify the Composition of Multicomponent Bacterial Samples

Fast and reliable identification of infectious disease agents is among the most important challenges for the healthcare system. The discrimination of individual components of mixed infections represents a particularly difficult task. In the current study we further expand the functionality of a ratiometric sensor array technology based on small-molecule environmentally-sensitive organic dyes, which can be successfully applied for the analysis of mixed bacterial samples. Using pattern recognition methods and data from pure bacterial species, we demonstrate that this approach can be used to quantify the composition of mixtures, as well as to predict their components with the accuracy of ~80% without the need to acquire additional reference data. The described approach significantly expands the functionality of sensor arrays and provides important insights into data processing for the analysis of other complex samples

CcpA regulates arginine biosynthesis in Staphylococcus aureus through repression of proline catabolism.

Staphylococcus aureus is a leading cause of community-associated and nosocomial infections. Imperative to the success of S. aureus is the ability to adapt and utilize nutrients that are readily available. Genomic sequencing suggests that S. aureus has the genes required for synthesis of all twenty amino acids. However, in vitro experimentation demonstrates that staphylococci have multiple amino acid auxotrophies, including arginine. Although S. aureus possesses the highly conserved anabolic pathway that synthesizes arginine via glutamate, we demonstrate here that inactivation of ccpA facilitates the synthesis of arginine via the urea cycle utilizing proline as a substrate. Mutations within putA, rocD, arcB1, argG and argH abolished the ability of S. aureus JE2 ccpA::tetL to grow in the absence of arginine, whereas an interruption in argJBCF, arcB2, or proC had no effect. Furthermore, nuclear magnetic resonance demonstrated that JE2 ccpA::ermB produced (13)C(5) labeled arginine when grown with (13)C(5) proline. Taken together, these data support the conclusion that S. aureus synthesizes arginine from proline during growth on secondary carbon sources. Furthermore, although highly conserved in all sequenced S. aureus genomes, the arginine anabolic pathway (ArgJBCDFGH) is not functional under in vitro growth conditions. Finally, a mutation in argH attenuated virulence in a mouse kidney abscess model in comparison to wild type JE2 demonstrating the importance of arginine biosynthesis in vivo via the urea cycle. However, mutations in argB, argF, and putA did not attenuate virulence suggesting both the glutamate and proline pathways are active and they, or their pathway intermediates, can complement each other in vivo

Inactivation of the Pta-AckA Pathway Causes Cell Death in \u3ci\u3eStaphylococcus aureus\u3c/i\u3e

During growth under conditions of glucose and oxygen excess, Staphylococcus aureus predominantly accumulates acetate in the culture medium, suggesting that the phosphotransacetylase-acetate kinase (Pta-AckA) pathway plays a crucial role in bacterial fitness. Previous studies demonstrated that these conditions also induce the S. aureus CidR regulon involved in the control of cell death. Interestingly, the CidR regulon is comprised of only two operons, both encoding pyruvate catabolic enzymes, suggesting an intimate relationship between pyruvate metabolism and cell death. To examine this relationship, we introduced ackA and pta mutations in S. aureus and tested their effects on bacterial growth, carbon and energy metabolism, cid expression, and cell death. Inactivation of the Pta-AckA pathway showed a drastic inhibitory effect on growth and caused accumulation of dead cells in both pta and ackA mutants. Surprisingly, inactivation of the Pta-AckA pathway did not lead to a decrease in the energy status of bacteria, as the intracellular concentrations of ATP, NAD+, and NADH were higher in the mutants. However, inactivation of this pathway increased the rate of glucose consumption, led to a metabolic block at the pyruvate node, and enhanced carbon flux through both glycolysis and the tricarboxylic acid (TCA) cycle. Intriguingly, disruption of the Pta-AckA pathway also induced the CidR regulon, suggesting that activation of alternative pyruvate catabolic pathways could be an important survival strategy for the mutants. Collectively, the results of this study demonstrate the indispensable role of the Pta-AckA pathway in S. aureus for maintaining energy and metabolic homeostasis during overflow metabolism

Tricarboxylic Acid Cycle-Dependent Regulation of \u3ci\u3eStaphylococcus epidermidis\u3c/i\u3e Polysaccharide Intercellular Adhesin Synthesis

Staphylococcus epidermidis is a major nosocomial pathogen primarily infecting immunocompromised individuals or those with implanted biomaterials (e.g., catheters). Biomaterial-associated infections often involve the formation of a biofilm on the surface of the medical device. In S. epidermidis, polysaccharide intercellular adhesin (PIA) is an important mediator of biofilm formation and pathogenesis. Synthesis of PIA is regulated by at least three DNA binding proteins (IcaR, SarA, and σB) and several environmental and nutritional conditions. Previously, we observed the environmental conditions that increased PIA synthesis decreased tricarboxylic acid (TCA) cycle activity. In this study, S. epidermidis TCA cycle mutants were constructed, and the function of central metabolism in PIA biosynthesis was examined. TCA cycle inactivation altered the metabolic status of S. epidermidis, resulting in a massive derepression of PIA biosynthetic genes and a redirection of carbon from growth into PIA biosynthesis. These data demonstrate that the bacterial metabolic status is a critical regulatory determinant of PIA synthesis. In addition, these data lead us to propose that the TCA cycle acts as a signal transduction pathway to translate external environmental cues into intracellular metabolic signals that modulate the activity of transcriptional regulators

EVALUATION OF ELASTIC-STRENGTH PROPERTIES OF CEMENT-EPOXY SYSTEMS

The relevance of the study is determined by the conditions of operation and completion of wells in modern conditions. In the process of well construction, the plugging material used to fasten casing strings experiences dynamic loads, as a result of which it loses its integrity, which leads to leakage of the annulus and subsequent crossflows of formation fluids. Dynamic loads include the dynamics of the drilling tool during normalization, operations for secondary opening, hydraulic fracturing, casing pressure testing after the waiting period for the cement stone to harden. The elastic properties of cement stone from various compositions were determined using ultrasonic evaluation methods, the strength properties were determined by destructive testing methods according to API 10B-2 / ISO 10426-2 standards. There are a number of works and industry solutions of well cementing contractors related to the creation of elastic cement systems, however, in many respects, these developments do not fully solve the identified problems and are dependent on imported components. The main aim: development of the composition of a cement slurry with increased elastic-strength properties from Russian components. Object: cement stone and its elastic-strength properties. Results. In the course of experimental studies, an increase in the bending strength and improvement in the elastic properties of cement-epoxy stone are noted when using epoxy resin as part of the cement system, the distribution of the resin in the composition of the cement stone using 3D X-ray scanning methods is determined, the advantages and disadvantages of additives-elasticizers are noted, concentrations of additives that improve the technological properties of cement mortar and stone are selected

Intergovernmental Relations and Diplomacy on the Western Mediterranean in 323-264 B.C.

В монографии рассматриваются военные и дипломатические контакты государств Западного Средиземноморья в период от смерти Александра Македонского до начала Первой Пунической войны. Автор анализирует связи Рима, Карфагена, Сиракуз между собой и с восточноэллинистическими державами, рассматривает развитие их дипломатической активности, изучает регулировавшие их отношения международно-правовые нормы

Methodology Approbation for the Overhead Power Lines Sag Determining by the Period of Conductor Owned Oscillations

The relevance of the problem is justified and the review of existing methods for determining the overhead line sag by the period of the conductor owned oscillations is conducted. The method of controlling the sag by the period of its own oscillations is briefly presented. The experimental installation for conducting full-scale tests is described, which includes the conductor (64 m), rigid fasteners at the points of conductor suspension, accelerometer, and temperature sensor mounted on the conductor, data from which are processed and recorded by the specialized software. The measurement method is explained with a detailed description. The conductor oscillations spectral analysis is performed. The results of experimental main harmonic frequency measurements, conductor, and changes in the sag are presented. A comparative results analysis showed the efficiency of the proposed method. The described method for determining the sag is easy to use (it is enough to install an accelerometer on the conductor and process data from it) and can be recommended for monitoring the condition of overhead power lines. The correlation of changes in the conductor oscillations spectral harmonics amplitude with temperature was studied. It is found that the correlation coefficient initially increases with the growth of the harmonics number. It is maximal for the ninth harmonic R = −0.9, and then slowly weakens, remaining between 0.9 and 0.8. This property of high-frequency harmonic oscillations can be used in the high-voltage lines condition diagnosis

Assessment of the Technical Condition of High-Voltage Insulators during Operation

During the operation process of high-voltage insulators, the characteristics of assessing their technical state are evaluated by using remote contactless monitoring and by subsequent forecasting of their residual life based on the developed set of diagnostic parameters of critical defects. Special attention is paid to the challenges of the practical application for remote contactless monitoring of high-voltage insulators’ current operating state. Measurements of characteristics for partial discharges on high-voltage insulators with various types of critical defects taken by electromagnetic and acoustic sensors are described. Based on the measurements, it was found that the unusual properties of the PD begin to manifest themselves starting from the intensities q ≥ 1.5–2 nC, and their maximum intensity can reach 5–7 nC. Up to PD intensities q ≤ 3 nC, most parameters of PD characteristics measured by electromagnetic and acoustic sensors correspond with an accuracy of 70–90%. It was found that for small defects with sizes d ≤ 300 μm in HVI, the PD intensity does not exceed 100 pC and depends little on the size of the defect. However, with an increase in the size of defects above 0.4–0.6 mm, a sharp rise in the intensity of the emerging VLPD begins