The multidrug efflux pump regulator AcrR directly represses motility in Escherichia coli

Efflux and motility are two key biological functions in bacteria. Recent findings have shown that efflux impacts flagellum biosynthesis and motility in Escherichia coli and other bacteria. AcrR is known to be the major transcriptional repressor of AcrAB-TolC, the main multidrug efflux pump in E. coli and other Enterobacteriaceae. However, the underlying molecular mechanisms of how efflux and motility are co-regulated remain poorly understood. Here, we have studied the role of AcrR in direct regulation of motility in E. coli. By combining bioinformatics, electrophoretic mobility shift assays (EMSAs), gene expression, and motility experiments, we have found that AcrR represses motility in E. coli by directly repressing transcription of the flhDC operon, but not the other flagellum genes/operons tested. flhDC encodes the master regulator of flagellum biosynthesis and motility genes. We found that such regulation primarily occurs by direct binding of AcrR to the flhDC promoter region containing the first of the two predicted AcrR-binding sites identified in this promoter. This is the first report of direct regulation by AcrR of genes unrelated to efflux or detoxification. Moreover, we report that overexpression of AcrR restores to parental levels the increased swimming motility previously observed in E. coli strains without a functional AcrAB-TolC pump, and that such effect by AcrR is prevented by the AcrR ligand and AcrAB-TolC substrate ethidium bromide. Based on these and prior findings, we provide a novel model in which AcrR senses efflux and then co-regulates efflux and motility in E. coli to maintain homeostasis and escape hazards. IMPORTANCE Efflux and motility play a major role in bacterial growth, colonization, and survival. In Escherichia coli, the transcriptional repressor AcrR is known to directly repress efflux and was later found to also repress flagellum biosynthesis and motility by Kim et al. (J Microbiol Biotechnol 26:1824-1828, 2016, doi: 10.4014/jmb.1607.07058). However, it remained unknown whether AcrR represses flagellum biosynthesis and motility directly and through which target genes, or indirectly because of altering the amount of efflux. This study reveals that AcrR represses flagellum biosynthesis and motility by directly repressing the expression of the flhDC master regulator of flagellum biosynthesis and motility genes, but not the other flagellum genes tested. We also show that the antimicrobial, efflux pump substrate, and AcrR ligand ethidium bromide regulates motility via AcrR. Overall, these findings support a novel model of direct co-regulation of efflux and motility mediated by AcrR in response to stress in E. coli.

Masculine men do not like feminine wording: The effectiveness of gendered wording in health promotion leaflets in the UK

Following mixed-methods sequential design and drawing on the message-audience congruence concept and homophily theory, across three studies in the UK, we examined the effect of gendered wording and endorser’s gender on the effectiveness of leaflets promoting walking. In Study 1, a mall-intercept study achieved 247 completed questionnaires. Results demonstrated that men and women indicated the highest behavioural intentions for communal wording presented by a male endorser. However, pairwise comparisons revealed that when the wording of the advert was agentic and the endorser was male, males indicated significantly higher scores of behavioural intentions compared with females. Attitude towards the ad for women was highest for communal wording/female endorser; for men it was for agentic wording/male endorser. In Study 2, consumers’ views towards the gendered content were explored in 20 semi-structured interviews. In study 3 we examined the impact of the respondent’s gender role identity on gendered content effectiveness. Overall, when controlled for level of gender role identity, only masculine males evaluated leaflets featuring communal wording negatively which suggests that wording matters only for masculine males, but not for other men and women. Theoretically, we identified that gender-based message-respondent congruence is not a necessary aspect of communications to be effective, except for one group: masculine males. Our study identified dominant gender role identity as a factor that explained respondents’ preferences for presented stimuli. Specifically, males who display masculine gender role identity differ in evaluations of communal wording from all other groups. Social and commercial marketers who target men and women with exercise-related services should consider the use of agentic wording endorsed by a male endorser when targeting masculine men to increase the likelihood of eliciting positive attitudes towards the communication. However, such distinctions should not be associated with differences in women’s evaluations or men who do not report masculine gender role identity.

Variation in the timing of Covid-19 communication across universities in the UK

During the Covid-19 pandemic, universities in the UK used social media to raise awareness and provide guidance and advice about the disease to students and staff. We explain why some universities used social media to communicate with stakeholders sooner than others. To do so, we identified the date of the first Covid-19 related tweet posted by each university in the country and used survival models to estimate the effect of university-specific characteristics on the timing of these messages. In order to confirm our results, we supplemented our analysis with a study of the introduction of coronavirus-related university webpages. We find that universities with large numbers of students are more likely to use social media and the web to speak about the pandemic sooner than institutions with fewer students. Universities with large financial resources are also more likely to tweet sooner, but they do not introduce Covid-19 webpages faster than other universities. We also find evidence of a strong process of emulation, whereby universities are more likely to post a coronavirus-related tweet or webpage if other universities have already done so.

A comparative study of the diagnostic accuracy of cone beam computed tomography and intraoral radiographic modalities for the detection of noncavitated caries

OBJECTIVES

The aim of this study was to determine the diagnostic accuracy of cone beam computed tomography (CBCT) in the detection of approximal and occlusal noncavitated carious lesions.

METHODS

A total of 135 extracted human posterior teeth were used. They were radiographed using the following: conventional film (Kodak Insight), a digital system (PSP plates Digora Optime, Soredex), and a CBCT system (NewTom 3G, Quantitative Radiology). All the images were assessed by two independent observers twice. Receiver operating characteristic analysis (Az) was used.

RESULTS

NewTom 3G 9″ CBCT was statistically inferior to conventional film and a digital system for the detection of approximal caries. NewTom 3G 9″ had significantly higher Az values than PSP plate (p < 0.05), but there were no statistically significant differences between the Az values for CBCT and film (p > 0.33) for occlusal surface caries.

CONCLUSION

The diagnostic accuracy of all three tested radiographic systems is low, and it is necessary to use other methods to improve early caries detection.

CLINICAL RELEVANCE

CBCT has found a wide application in different fields of dentistry. The report from a CBCT examination performed for any of these reasons should include all abnormal findings, and the detection of noncavitated caries lesions is especially important because it facilitates the use of noninvasive treatment.

Microscopic evaluation of the interface between glass-ionomer cements and tooth structures prepared using conventional instruments and the atraumatic restorative treatment (ART) technique

OBJECTIVE

The purpose of this study was to evaluate the effect of cavity preparation using hand instruments and conventional rotary instruments on the bonding of glass-ionomer cements to formerly carious teeth.

METHOD AND MATERIALS

In 2 experimental groups (12 teeth each with primary caries) caries was removed and cavities prepared using hand instruments according to the atraumatic restorative treatment (ART) technique or conventional rotary instruments. In the control group (12 caries-free teeth) Class 1 cavities were prepared using conventional instrumentation. Cavities in all teeth were restored with 1 of the commercial glass-ionomer cements designed for use with the ART technique, either Fuji IX (GC) or Ketac Molar (3M Espe). After 21 days of storage in physiologic saline at 37 degrees C, 3 400-microm-thick slices from each tooth were stained using the Mallory method and evaluated using a light transmitting microscope.

RESULTS

In all samples, a region of interaction was observed between the cement and dentin and enamel. However, the interface in teeth from which caries had been removed was different from that in the control group. All were stained using Mallory staining, but only teeth which had been carious showed coloration. No differences were found in intensity of color or appearance between the cavity preparation techniques.

CONCLUSION

The occurrence of caries in a tooth alters the bonding behavior of glass ionomers to that tooth. The method of caries removal (ART or conventional preparation) does not influence the quality of the interface between a glass ionomer and either dentin or enamel.

The Clinical Repair of Teeth Using Direct Filling Materials: Engineering Considerations

This paper reviews the way in which teeth damaged by caries may be repaired clinically. The mechanical effects of caries are described, as are the materials available to repair the damage caused by this disease. Studies are reported which have shown that caries reduces the compressive strength of the tooth to less than 50 per cent of its original value and that, by use of appropriate materials and placement techniques, this can be restored to some 80 per cent of this value. However, very few studies have been carried out which view tooth repair from an engineering perspective. Instead, emphasis is placed on determining clinical durability of repairs. This is related to repair strength but brings in other factors, such as the oral hygiene of the patient. Despite this complication, durability studies show that modern restorative materials perform well under clinical conditions, from which it may be concluded that the repair process allows a structure to be fabricated that is essentially sound from an engineering view-point, even if inferior to the original tooth structure provided by nature.

[Smoking addiction and patients' motivation to quit it among attenders of the Saldent 2006 conference]

This paper presents the results of a survey carried out among those attending the Saldent 2006 conference. The questionnaire used for this purpose included questions concerning smoking among dentists, permission to smoke in the dental surgery, patients motivation to quit smoking, knowledge regarding the harmful effect of smoking on the oral cavity and the possible need for teaching preventive measures on the subject during under- and postgraduate education. The results showed that when compared with those obtained 6 years ago smoking among the dentists has declined. Answers to the questions concerning the influence of smoking on oral cavity showed a high awareness of this danger among the questionnaire respondents. Also the high number of dentists who are motivating patients against smoking confirms the opinion that in the planning of antismoking programs dentists can play a significant role.

The release of ions by compomers under neutral and acidic conditions

Three commercial compomers have been studied for their interaction with aqueous solutions (i.e. water at pH 5.9 and lactic acid at pH 2.7). Light-cured discs of these materials (12.8 diameter x 1 mm depth; Dyract AP, Compoglass F and F2000) were prepared and stored in 5 cm(3) of either water or lactic acid at pH 2.7. After 1 week, mass changes, pH changes and ion-release were determined. For the specimens stored in water, the effect of maturation under neutral conditions was studied by continuing storage for 3 months, followed by storage in lactic acid for a further week after which ion release and pH change were determined. Student's t-test was used to determine statistical significance of any changes observed. All three cured compomers absorbed water and altered the pH of the solutions, though this was statistically significant only in lactic acid. They were found to release Na, Ca, Sr, Al, Si, P and F ions, with greater amounts being released in acidic conditions than neutral ones. More fluoride was released in acid than in water, but the proportion of free (uncomplexed) fluoride to bound (complexed) fluoride was much lower than in neutral conditions. This was attributed to the formation of strong complexes with aluminium. Maturing specimens for 3 months made very little difference to their interaction with the acid solution, except for the total release of fluoride, which was some two to three greater than from the immature specimens.

The interaction of glass-ionomer cements containing vinylphosphonic acid with water and aqueous lactic acid

A glass-ionomer cement containing an acrylic acid/vinyl phosphonic acid copolymer, has been investigated for its interaction with water and with aqueous lactic acid and the results compared with those from conventional glass-ionomers based on polyacrylic acid. Cylindrical specimens (12 mm high x 6 mm diameter) were placed in 8 cm3 of aqueous lactic acid (20 mmol dm(-3); pH 2.7) for 1 week, at the end of which the pH was determined. Each specimen was then placed in a fresh 8 cm3 volume of lactic acid and the pH determined after a further week. This procedure was continued for a total of 13 weeks for each specimen. Experiments were also carried out on similar specimens exposed to 8 cm3 of water for 1 week only. Further experiments were carried out in which discs of cement were exposed to thin films (0.15 mm) of lactic acid at pH 4.5, with pH values determined at 30 s, 1, 2, 5 and 10 min. After 1 week, cements had changed the pH of the lactic acid to a mean value of 3.63 (SD 0.08) while in weeks 2-13 they changed it to a mean value of 3.31 (SD 0.11). After 1 week in aqueous lactic acid the cements had gained mass by a mean of 1.26% (SD 0.59%) compared with 1.22% (SD 0.14%) in water. After 13 weeks in lactic acid, cements had lost a mean of 2.83% (SD 0.74%) in mass. Thin films of aqueous lactic acid changed from pH 4.5-5.1 at 30 s and to a steady value of 5.6 (SD 0.3) between 2 and 10 min. These results were similar to those for conventional glass-ionomer cements based on carboxylic acid polymers. Hence, it was concluded that the presence of the vinylphosphonic acid units made no significant difference to the interaction of cements with aqueous solutions.

The rate of change of pH of lactic acid exposed to glass-ionomer dental cements

The rate of change of pH of aqueous lactic acid at pH 4.2-4.5 (i.e. a little below that of active caries in vivo) in contact with disks of various commercial glass-ionomer cements has been determined in two configurations. In the first of them, a thin film set-up, 20 microl of solution was spread across the surface of a cement disk (diameter: 13 mm), and its pH determined by pressing a flat-ended electrode against the film at varying time intervals. In the second, a similar disk was immersed in 1.5 ml of solution, removed after varying time intervals, after which the pH of the solution was measured using a round-ended electrode. The latter measurement was more reliable, in that the pH electrode had time to equilibrate, whereas the former was more realistic because the film was approximately the same thickness as that of saliva on a tooth surface. Both series of experiments showed measurable differences in pH after only 30 s, with the thin-film configuration showing a range of pH changes of 0.5-1.2 units depending on the cement and the small volume configuration showing a range of 0.1-0.5 units, also depending on the cement. After 10 min, in the small volume experiments, the pH had generally increased further. The extent and speed of the change in pH led to the conclusion that ability of glass-ionomers to increase pH is likely to be an important mechanism of caries protection under clinical conditions.

Storage of polyacid-modified resin composites ("compomers") in lactic acid solution

OBJECTIVES

The aim of this study was to determine the interaction of four polyacid-modified resin composites with aqueous lactic acid solutions, and to compare changes with those for a glass-ionomer cement and a conventional resin composite.

METHODS

For each material, namely Compoglass F, Dyract AP, Hytac and Ana Compomer, plus AquaCem (glass-ionomer cement) and Pekafil (conventional composite resin), five cylindrical specimens of 4 mm diameter x 6 mm height were prepared and weighed. They were stored individually in 2.0 cm3 of 0.02 mol l-1 lactic acid solution for 1 week then the pH was determined and the specimens reweighed. The lactic acid solution was replenished, and the specimens were stored for a further week, after which the pH and specimen weights were again measured. This was repeated at 1 week intervals until the specimens were 6 weeks old. Differences were analysed by ANOVA followed by Newman-Keuls post hoc analysis.

RESULTS

All four polyacid-modified composites increased the pH of the solutions at all time intervals by at least 0.26 pH units (significant to at least p < 0.01). This effect was similar to that of the glass-ionomer (but significantly less, p < 0.05) while significantly greater (p < 0.05) than that for the composite, Pekafil, which, by contrast, had no effect on pH. The observed rise in pH reduced significantly over time (ANOVA, p < 0.05). After 1 week, all pH changes were accompanied by net reductions in specimen mass, indicating susceptibility to acid erosion. Hytac was significantly more resistant to this erosion than the other materials; conversely, it had the least effect on solution pH.

SIGNIFICANCE

These results show that polyacid-modified resin composites neutralise lactic acid in vitro but suffer erosion in the process.

The long-term interaction of dental cements with lactic acid solutions

A study of the interaction of dental cements with lactic acid solutions has been carried out in which individual cement specimens were repeatedly exposed to 20 mmol dm(-3) lactic acid for periods of a week. After each week of storage, the mass of the specimens was recorded and the pH of the solution determined. The glass-ionomers showed an initial increase in mass, followed by a decline that became steady from 6 weeks. Zinc polycarboxylate and zinc phosphate cements, by contrast, showed no early gain in mass, but eroded steadily more or less from the start of their exposure to lactic acid. For all cements, acid erosion followed linear kinetics, at rates ranging from 0.5%/week for the zinc phosphate to 0.28%/week for one of the glass-ionomers, Chelonfil (ESPE, Germany). At the end of six months, the zinc phosphate had lost 14.2% of its initial mass, the zinc polycarboxylate 9.9% and the glass-ionomers between 6.2 and 7.2%. Erosion was accompanied on every occasion by neutralization of the acid solution. Both erosion and neutralization continued steadily throughout the experiment. The effectiveness of neutralization was in the following order: zinc polycarboxylate>zinc phosphate>glass-ionomer. The pH change in Week 1 was much greater for the glass-ionomers and the zinc polycarboxylate than in all subsequent weeks.

A preliminary study of the effect of glass-ionomer and related dental cements on the pH of lactic acid storage solutions

Glass-ionomer cements, both self-hardening and resin-modified, have been shown to increase the pH of lactic acid solutions in which they are stored. Similar results have been obtained for a zinc phosphate and a zinc polycarboxylate cement. The pH was increased over a period of 7 days by between 1.54 and 2.65 pH units from an initial value of pH of 2.60, depending on the cement. It is concluded that, as a result of this ability to neutralize surrounding aqueous solutions, these materials may have the beneficial effect in vivo of inhibiting caries development. In the case of glass-ionomers, this mechanism might complement that of fluoride release.

Results of epidemiological examinations of the temporomandibular joint in adolescents and young adults

An epidemiological investigation of the temporomandibular joint in 800 persons was undertaken, including two groups of 400 persons aged 15-18 and 19-22 years. The numbers of boys and girls was about the same. Interview and clinical examination comprised morphological and functional features of the stomatognathic system. The TMJ examination carried out included mandibular movements, pain and sound symptoms. The results of the examinations were noted, counted by electronic methods and statistically analysed. From the material, two groups were selected: without TMJ symptoms (OTMJ group) and with TMJ disorders (TMJ group). TMJ disorders were evident in 67.62% of the examined persons and this was common to both age groups. In groups with TMJ disorders a significant incidence of girls was found. In groups with TMJ disorders the number of statistically significant pathological features in the stomatognathic system increased with age. TMJ disorders appeared in both age groups in various forms, separately or in combination, with different frequency. With reference to the number and kind of symptoms obtained on interview and/or on clinical examination, four degrees of intensity of TMJ disorders have been defined and their incidence discussed.

Musculo-articular disorders of the stomatognathic system in school children examined according to clinical criteria

The present investigations were undertaken for establishing the frequency of musculo-articular disorders of the stomatognathic system in healthy children as well as determining their features and degree. The study covered 500 children from Warsaw's primary schools--250 children aged 6-8 years and 250 aged 13-15 years. An incidence of disorder of 56-4 and 67-6% was found in the groups of younger and older children, respectively; their number and severity being significantly higher among the latter. The chi-square test showed no relation between the disorders of the temporomandibular joint and malocclusion or the premature loss of teeth in the group of younger children; in the older group the correlation was significant but of very low degree. The suggestion is made that the correlation between musculo-articular disorders, malocclusions and loss of teeth, is probably determined by the length of time during which the dysfunction is exerting its effect.