Indigenizing and Ruralizing NCI Screen to Save Program: Resources, Optimizing Outreach, Teaching, Science (ROOTS).

Colorectal cancer (CRC) is a complex health disparity in many Indigenous and rural populations. While it affects anyone regardless of race, age, gender, or other common differences among people, Indigenous and rural populations are at a higher risk of dying from colorectal cancer. An NCI Screen to Save (S2S) program was culturally tailored to promote awareness and knowledge of colorectal cancer and screening in both Indigenous and rural communities across a sector in Northeastern USA. Indigenous and rural community outreach teams at an NCI-designated cancer center partnered with a community advisory board to provide an indigenized/ruralized version of the NCI Screen to Save program delivered to both Indigenous and rural/suburban communities. In total, n = 79 pre/post surveys were obtained from n = 82 participants, who had an average age of 49 years. Findings demonstrated that Indigenous/rural participants in both off-territory/non-reservation communities and a tribal community that received a culturally tailored version of NCI's S2S program were able to identify both smoking and tobacco use along with lack of physical activity as risk factors for colorectal cancer. Post-intervention, participants reported being more likely to increase physical activity. Most importantly, participants said they would be more likely to be screened for colorectal cancer along with their family and friends based on their cancer screening experiences. Culturally tailored CRC messaging is an effective means for increasing screening intentions and decreasing cancer health disparities among both indigenous and rural populations. Future research should include the relationship of diet to obesity-related cancers, greater integration of Indigenous-rural patient navigation programs, creation of more information on genetic screening, and quality improvement to service translational science initiatives.

Importance of biofilm formation for promoting plant growth under salt stress in Pseudomonas putida KT2440.

An underutilized experimental design was employed to isolate adapted mutants of the model bacterium Pseudomonas putida KT2440. The design involved subjecting a random pool of mini-Tn5 mutants of P. putida KT2440 to multiple rounds of selection in the rhizosphere of soybean plants irrigated with a NaCl solution. The isolated adapted mutants, referred to as MutAd, exhibited a mutation in the gene responsible for encoding the membrane-binding protein LapA, which plays a role in the initial stages of biofilm formation on abiotic surfaces. Two MutAd bacteria, MutAd160 and MutAd185, along with a lapA deletion mutant, were selected for further investigation to examine the impact of this gene on salt tolerance, rhizosphere fitness, production of extracellular polymeric substances (EPS), and promotion of plant growth. Despite the mutants' inability to form biofilms, they were able to attach to soybean seeds and roots. The MutAd bacteria demonstrated an elevated production of EPS when cultivated under saline conditions, which likely compensated for the absence of biofilm formation. MutAd185 bacteria exhibited enhanced root attachment and promoted the growth of soybean plants in slightly saline soils. The proposed experimental design holds promise for expediting bacterial adaptation to the rhizosphere of plants under specific environmental conditions, identifying genetic mutations that enhance bacterial fitness in those conditions, and thereby increasing their capacity to promote plant growth.

Understanding social network support, composition, and structure among cancer caregivers.

OBJECTIVE: We examined the social network support, composition, and structure of pediatric cancer caregivers. METHODS: We used a self-report survey to collect egocentric social network data from 107 caregivers of pediatric cancer patients and calculated descriptive statistics to examine cancer-related support network composition, function, and structure. We then ran logistic regressions to examine the relationships between network characteristics and overall satisfaction with social support. RESULTS: Family members were the most common source of emotional support and logistical support, and health care providers were the most common source of informational support. Participants perceived the "most helpful" forms of support as being: (1) emotional support from family and health care providers; (2) informational support from health care providers and other cancer caregivers; and (3) logistical support from family. Overall, caregivers wished that 9.8% of their network ties had provided more support, with family members being the most common alter type to disappoint caregivers and offer less support than needed/expected. Caregivers who reported higher network disappointment (having network members who offered less support than needed/expected) were significantly less satisfied with emotional support than those with lower network disappointment (Odds Ratio = 0.18, p = 0.02), and caregivers with higher network disappointment were significantly less satisfied with logistical support compared to those with lower network disappointment (Odds Ratio = 0.14, p = 0.01). CONCLUSION: Our results show differences in the nature of social support provided by different types of network members. These findings have implications for tailoring social network interventions to improve caregiver and family outcomes.

Less is more: Enterobactin concentration dependency in copper tolerance and toxicity.

The ability of siderophores to play roles beyond iron acquisition has been recently proven for many of them and evidence continues to grow. An earlier work showed that the siderophore enterobactin is able to increase copper toxicity by reducing Cu2+ to Cu+, a form of copper that is more toxic to cells. Copper toxicity is multifaceted. It involves the formation of reactive oxygen species (ROS), mismetallation of enzymes and possibly other mechanisms. Given that we previously reported on the capacity of enterobactin to alleviate oxidative stress caused by various stressors other than copper, we considered the possibility that the siderophore could play a dual role regarding copper toxicity. In this work, we show a bimodal effect of enterobactin on copper toxicity (protective and harmful) which depends on the siderophore concentration. We found that the absence of enterobactin rendered Escherichia coli cells more sensitive to copper, due to the reduced ability of those cells to cope with the metal-generated ROS. Consistently, addition of low concentrations of the siderophore had a protective effect by reducing ROS levels. We observed that in order to achieve this protection, enterobactin had to enter cells and be hydrolyzed in the cytoplasm. Further supporting the role of enterobactin in oxidative stress protection, we found that both oxygen and copper, induced the expression of the siderophore and also found that copper strongly counteracted the well-known downregulation effect of iron on enterobactin synthesis. Interestingly, when enterobactin was present in high concentrations, cells became particularly sensitive to copper most likely due to the Cu2+ to Cu+ reduction, which increased the metal toxicity leading to cell death.

An initial investigation of using smartphone-enabled micro-temporal data collection to increase acceptability, feasibility, and validity of research on cancer caregiving.

PURPOSE: Smartphone-enabled micro-temporal data collection has potential to increase reliability, validity, and feasibility of participant-reported data and is a promising strategy for pediatric oncology supportive care and quality-of-life research. Given the demands of pediatric cancer caregiving, we sought to understand the feasibility and acceptability of smartphone data collection that included short surveys administered daily for 14 days via text message link. METHODS: We recruited pediatric cancer caregivers, whose children (ages 0-18 years) were on active treatment, to complete a 14-day daily survey study via smartphone. We implemented our study procedures and examined feasibility through study enrollment rates, reasons for refusal, retention rates, number of reminders and number of completed surveys. We examined acceptability using caregiver ratings of survey length, burden, and ease of completion on a smartphone. RESULTS: We recruited (N = 75) caregivers to the study and had an 84% enrollment rate. Reasons for declining participation included passive refusal (n = 13) and too busy (n = 1). The participant retention rate was 100% and compliance with daily survey completion was 99%. Most surveys were completed following two prompts and took participants 5 minutes or less to complete. Caregivers rated the surveys as easy to complete, low burden, and just right in length. CONCLUSION: A daily self-report, using a brief (≤5 minutes) survey administered on a smartphone via text message prompt, is a feasible and acceptable method. Future research should extend these findings to understand the generalizability across pediatric cancer caregiving contexts.

Behavioral parenting skills as a novel target for improving medication adherence in young children: Feasibility and acceptability of the CareMeds intervention.

In pediatric cancer care, medication non-adherence is a significant driver of avoidable suffering and death. There is a lack of interventions designed for families of young children, where patient medication refusal/avoidance is a common barrier to adherence. We developed the CareMeds intervention which focuses on caregiver skills training to help young children take medicine calmly and without use of restraint techniques. The goal of this preliminary study was to assess the acceptability and feasibility of the CareMeds intervention. Caregivers of pediatric cancer patients (ages 2-10) whose children were on a home-based oral medication regimen were recruited to participate. Feasibility was examined through study enrollment and retention rates as well as reasons for refusal and drop out. Acceptability was evaluated through usability of and engagement with intervention components and an acceptability questionnaire. Feasibility: We recruited N = 9 caregivers to participate in this intervention pilot study and had a 75% enrollment rate. Reasons for declining included scheduling concerns (n = 2) and lack of interest (n = 1). The participant retention rate was 100% with 100% adherence to intervention sessions. Acceptability: Parents rated the sessions and resource materials as acceptable and reported frequent use of skills taught in the intervention. The CareMeds intervention is an acceptable and feasible strategy for caregivers of pediatric cancer patients and warrants future research to examine the efficacy of behavioral parenting skills interventions to improve medication adherence in young children.

Antimicrobial activity of MccJ25(G12Y) against gram-negative foodborne pathogens in vitro and in food models.

The use of bacteriocins is a promising alternative to improve food security through the biocontrol of food pathogens and spoilage microorganisms. Gram-negative produced microcin J25(G12Y), known as (MccJ25(G12Y)) is a variant of the well-studied and characterized antimicrobial peptide, microcin J25 (MccJ25). In the present work, we explored the activity of this microcin against Gram-negative bacteria linked to foodborne diseases. We evaluated the in vitro antimicrobial activity of MccJ25(G12Y) in solid medium against a collection of pathogenic and food-altering strains and studied its activity and stability in meat and dairy food systems. We show that MccJ25(G12Y) exhibited the same in vitro antimicrobial spectrum as its parental microcin (MccJ25) against different Gram-negative foodborne pathogens and spoilage strains. We highlight that low concentrations of MccJ25(G12Y) between 0.45 and 29.4 µM were able to inhibit a substantial number of pathogens, including Salmonella, Escherichia, Shigella and Enterobacter genus. We also demonstrate the antimicrobial effectiveness of the peptide against Escherichia coli O157:H7 NCTC 12900, Enterobacter cloacae CECT 194, and Salmonella enterica CECT 4396 in fish and beef burgers and yogurt. MccJ25(G12Y) was added or not to food matrices inoculated with the foodborne pathogens at 105 CFU/g or mL. Afterward, food products were stored at 4 °C and selective media for the specific enumeration were used to determine the antimicrobial susceptibility of each pathogen to MccJ25(G12Y). The viability of the three pathogens was significantly reduced in the different food biological environments. In yogurt, the peptide decreased E. coli numbers on day 5 by about 4 log 10 CFU/mL as compared to non-treated samples. For S. enterica and E. cloacae no viable cells were detected at the end of the treatment. Adding MccJ25(G12Y) to fish burgers decreased E. cloacae numbers during storage 2 log10 CFU/g on the first day, reaching a difference of about 5 log 10 CFU/g after 10 days compared to non-treated control. Finally, the peptide decreased E. coli O157:H7 numbers on the beef burgers samples during storage on day 10 by about 3 log 10 CFU/g as compared to non-treated samples. The stability analysis demonstrated that MccJ25(G12Y) is capable of remaining active in these food matrices for a considerable time during the storage at refrigeration temperatures. These results reinforce the studies on the potential applicability of this microcin as a biopreservative in the food industry.

Plant growth promotion by Pseudomonas putida KT2440 under saline stress: role of eptA.

New strategies to improve crop yield include the incorporation of plant growth-promoting bacteria in agricultural practices. The non-pathogenic bacterium Pseudomonas putida KT2440 is an excellent root colonizer of crops of agronomical importance and has been shown to activate the induced systemic resistance of plants in response to certain foliar pathogens. In this work, we have analyzed additional plant growth promotion features of this strain. We show it can tolerate high NaCl concentrations and determine how salinity influences traits such as the production of indole compounds, siderophore synthesis, and phosphate solubilization. Inoculation with P. putida KT2440 significantly improved seed germination and root and stem length of soybean and corn plants under saline conditions compared to uninoculated plants, whereas the effects were minor under non-saline conditions. Also, random transposon mutagenesis was used for preliminary identification of KT2440 genes involved in bacterial tolerance to saline stress. One of the obtained mutants was analyzed in detail. The disrupted gene encodes a predicted phosphoethanolamine-lipid A transferase (EptA), an enzyme described to be involved in the modification of lipid A during lipopolysaccharide (LPS) biosynthesis. This mutant showed changes in exopolysaccharide (EPS) production, low salinity tolerance, and reduced competitive fitness in the rhizosphere.

A preliminary test of a brief intervention to lessen young adults' cannabis use: Episode-level smartphone data highlights the role of protective behavioral strategies and exercise.

Brief interventions are increasingly being used to help young adults to moderate their cannabis use. We conducted a randomized clinical trial of a brief (4 weekly sessions), in-person intervention that included a smartphone application that reinforced the use of protective behavioral strategies (PBSs) to lessen cannabis use. Young adults (N = 37; 24 men) who regularly used cannabis were randomized to 2 intervention conditions rooted in cognitive-behavioral therapy (CBT) and motivational enhancement therapy (MET). Along with learning CBT + MET strategies, participants in 1 of the conditions were instructed to engage in exercise. All participants used smartphone-based ecological momentary assessment to provide episode-level reports about use of cannabis and PBSs. Two multilevel structural equation models were run to test the study hypotheses that (a) cannabis use would be reduced over the course of the 6-month study, (b) reductions would be moderated by intervention condition, and (c) episode-level PBS use would predict episode-level cannabis use. Participants reduced their cannabis use by approximately 1 half of a standard joint per time point. The MET + CBT + Exercise condition reduced cannabis use to a greater degree than did the MET + CBT condition. With episode-level PBS use in the model, reductions in cannabis use were independent of intervention condition. Our findings suggest that young adults will engage with a smartphone app that serves as a component of an in-person intervention to moderate their cannabis use. Intervention content that promotes the use of PBSs and exercise facilitates reductions in cannabis use. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Effects of exercise on experimentally manipulated craving for cannabis: A preliminary study.

Cannabis is the most commonly used illicit drug in the United States, and craving for cannabis is related to cannabis use. Exercise has been demonstrated to reduce craving for substances. To examine the effects of exercise on cannabis craving, we conducted a 3-week within-subject crossover experiment. Young-adult men (n = 35) and women (n = 11), age 18-25 years (M = 20.76, SD = 1.68), who regularly (≥3 times per week) used cannabis participated in a cue exposure paradigm to stimulate craving. After each of three separate craving inductions, they completed a 10-min bout of exercise that varied in intensity (rest, moderate, vigorous). Craving was assessed before and after the induction, immediately following the exercise, and at three 10-min intervals (total of 30 min). Results of condition-specific, repeated measures analyses of variance showed nonsignificant reductions in immediate postexercise craving for the moderate and vigorous conditions. We used latent growth modeling to examine the trajectory of craving rebound during the 30 min following exercise and explored the effect of baseline weekly cannabis use in predicting craving rebound. Within 30 min postexercise, craving rebounded for both the moderate, F(3, 135) = 9.10, p < .01, and vigorous, F(3, 135) = 3.48, p < .05, conditions. We found that among cannabis users reporting larger quantities of typical weekly cannabis use, craving rebounded more quickly following vigorous than moderate exercise, b = 0.02, SE = 0.02, 95% confidence interval [0.00, 0.06]. The findings suggest that moderate exercise may be useful for reducing craving, particularly among those who use larger quantities of cannabis. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Beneficial rhizobacteria immobilized in nanofibers for potential application as soybean seed bioinoculants.

Seed inoculation with plant growth promoting rhizobacteria (PGPR) is an ideal tool to supply the soil with a high density of beneficial microorganisms. However, maintaining viable microorganisms is a major problem during seed treatment and storage. In this work, an evaluation was made of the effect of bacterial immobilization in nanofibers on the stability (viability and maintenance of beneficial properties) of two potential PGPR, Pantoea agglomerans ISIB55 and Burkholderia caribensis ISIB40. Moreover, the impact of soybean seed coating with nanofiber-immobilized rhizobacteria on bacterial survival during seed storage and on germination and plant growth parameters was determined. Bacterial nanoimmobilization and subsequent seed coating with nanofiber-immobilized rhizobacteria were carried out by electrospinning. The results demonstrate that this technique successfully immobilized P. agglomerans ISIB55 and B. caribensis ISIB40 because it did not affect the viability or beneficial properties of either rhizobacteria. Seed coating with nanofiber-immobilized rhizobacteria improved P. agglomerans ISIB55 and B. caribensis ISIB40 survival on seeds stored for 30 days and contributed to the successful colonization of both bacteria on the plant root. Moreover, seed coating with P. agglomerans ISIB55 increased germination, length and dry weight of the root. Furthermore, seed coating with B. caribensis ISIB40 increased leaf number and dry weight of the shoot. Therefore, the technique applied in the present work to coat seeds with nanofiber-immobilized PGPR could be considered a promising eco-friendly approach to improve soybean production using a microbial inoculant.

The effects of perceived quality on behavioral economic demand for marijuana: A web-based experiment.

BACKGROUND: Given the growing legalization of recreational marijuana use and related increase in its prevalence in the United States, it is important to understand marijuana's appeal. We used a behavioral economic (BE) approach to examine whether the reinforcing properties of marijuana, including "demand" for marijuana, varied as a function of its perceived quality. METHODS: Using an innovative, Web-based marijuana purchase task (MPT), a sample of 683 young-adult recreational marijuana users made hypothetical purchases of marijuana across three qualities (low, mid and high grade) at nine escalating prices per joint, ranging from $0/free to $20. RESULTS: We used nonlinear mixed effects modeling to conduct demand curve analyses, which produced separate demand indices (e.g., Pmax, elasticity) for each grade of marijuana. Consistent with previous research, as the price of marijuana increased, marijuana users reduced their purchasing. Demand also was sensitive to quality, with users willing to pay more for higher quality/grade marijuana. In regression analyses, demand indices accounted for significant variance in typical marijuana use. CONCLUSIONS: This study illustrates the value of applying BE theory to young adult marijuana use. It extends past research by examining how perceived quality affects demand for marijuana and provides support for the validity of a Web-based MPT to examine the appeal of marijuana. Our results have implications for policies to regulate marijuana use, including taxation based on the quality of different marijuana products.

Enterobactin as Part of the Oxidative Stress Response Repertoire.

Microorganisms produce siderophores to facilitate iron uptake and even though this trait has been extensively studied, there is growing evidence suggesting that siderophores may have other physiological roles aside from iron acquisition. In support of this notion, we previously linked the archetypal siderophore enterobactin with oxidative stress alleviation. To further characterize this association, we studied the sensitivity of Escherichia coli strains lacking different components of the enterobactin system to the classical oxidative stressors hydrogen peroxide and paraquat. We observed that strains impaired in enterobactin production, uptake and hydrolysis were more susceptible to the oxidative damage caused by both compounds than the wild-type strain. In addition, meanwhile iron supplementation had little impact on the sensitivity, the reducing agent ascorbic acid alleviated the oxidative stress and therefore significantly decreased the sensitivity to the stressors. This indicated that the enterobactin-mediated protection is independent of its ability to scavenge iron. Furthermore, enterobactin supplementation conferred resistance to the entE mutant but did not have any protective effect on the fepG and fes mutants. Thus, we inferred that only after enterobactin is hydrolysed by Fes in the cell cytoplasm and iron is released, the free hydroxyl groups are available for radical stabilization. This hypothesis was validated testing the ability of enterobactin to scavenge radicals in vitro. Given the strong connection between enterobactin and oxidative stress, we studied the transcription of the entE gene and the concomitant production of the siderophore in response to such kind of stress. Interestingly, we observed that meanwhile iron represses the expression and production of the siderophore, hydrogen peroxide and paraquat favour these events even if iron is present. Our results support the involvement of enterobactin as part of the oxidative stress response and highlight the existence of a novel regulation mechanism for enterobactin biosynthesis.

A behavioral economic approach to assessing demand for marijuana.

In the United States, marijuana is the most commonly used illicit drug. Its prevalence is growing, particularly among young adults. Behavioral economic indices of the relative reinforcing efficacy (RRE) of substances have been used to examine the appeal of licit (e.g., alcohol) and illicit (e.g., heroin) drugs. The present study is the first to use an experimental, simulated purchasing task to examine the RRE of marijuana. Young-adult (M age = 21.64 years) recreational marijuana users (N = 59) completed a computerized marijuana purchasing task designed to generate demand curves and the related RRE indices (e.g., intensity of demand-purchases at lowest price; Omax-max. spent on marijuana; Pmax-price at which marijuana expenditure is max). Participants "purchased" high-grade marijuana across 16 escalating prices that ranged from $0/free to $160/joint. They also provided 2 weeks of real-time, ecological momentary assessment reports on their marijuana use. The purchasing task generated multiple RRE indices. Consistent with research on other substances, the demand for marijuana was inelastic at lower prices but became elastic at higher prices, suggesting that increases in the price of marijuana could lessen its use. In regression analyses, the intensity of demand, Omax, and Pmax, and elasticity each accounted for significant variance in real-time marijuana use. These results provide support for the validity of a simulated marijuana purchasing task to examine marijuana's reinforcing efficacy. This study highlights the value of applying a behavioral economic framework to young-adult marijuana use and has implications for prevention, treatment, and policies to regulate marijuana use.

The alternative role of enterobactin as an oxidative stress protector allows Escherichia coli colony development.

Numerous bacteria have evolved different iron uptake systems with the ability to make use of their own and heterologous siderophores. However, there is growing evidence attributing alternative roles for siderophores that might explain the potential adaptive advantages of microorganisms having multiple siderophore systems. In this work, we show the requirement of the siderophore enterobactin for Escherichia coli colony development in minimal media. We observed that a strain impaired in enterobactin production (entE mutant) was unable to form colonies on M9 agar medium meanwhile its growth was normal on LB agar medium. Given that, neither iron nor citrate supplementation restored colony growth, the role of enterobactin as an iron uptake-facilitator would not explain its requirement for colony development. The absence of colony development was reverted either by addition of enterobactin, the reducing agent ascorbic acid or by incubating in anaerobic culture conditions with no additives. Then, we associated the enterobactin requirement for colony development with its ability to reduce oxidative stress, which we found to be higher in media where the colony development was impaired (M9) compared with media where the strain was able to form colonies (LB). Since oxyR and soxS mutants (two major stress response regulators) formed colonies in M9 agar medium, we hypothesize that enterobactin could be an important piece in the oxidative stress response repertoire, particularly required in the context of colony formation. In addition, we show that enterobactin has to be hydrolyzed after reaching the cell cytoplasm in order to enable colony development. By favoring iron release, hydrolysis of the enterobactin-iron complex, not only would assure covering iron needs, but would also provide the cell with a molecule with exposed hydroxyl groups (hydrolyzed enterobactin). This molecule would be able to scavenge radicals and therefore reduce oxidative stress.

Analytical Problems and Suggestions in the Analysis of Behavioral Economic Demand Curves.

Behavioral economic demand curves (Hursh, Raslear, Shurtleff, Bauman, & Simmons, 1988) are innovative approaches to characterize the relationships between consumption of a substance and its price. In this article, we investigate common analytical issues in the use of behavioral economic demand curves, which can cause inconsistent interpretations of demand curves, and then we provide methodological suggestions to address those analytical issues. We first demonstrate that log transformation with different added values for handling zeros changes model parameter estimates dramatically. Second, demand curves are often analyzed using an overparameterized model that results in an inefficient use of the available data and a lack of assessment of the variability among individuals. To address these issues, we apply a nonlinear mixed effects model based on multivariate error structures that has not been used previously to analyze behavioral economic demand curves in the literature. We also propose analytical formulas for the relevant standard errors of derived values such as P max, O max, and elasticity. The proposed model stabilizes the derived values regardless of using different added increments and provides substantially smaller standard errors. We illustrate the data analysis procedure using data from a relative reinforcement efficacy study of simulated marijuana purchasing.

Functional and structural study of the dimeric inner membrane protein SbmA.

SbmA protein has been proposed as a dimeric secondary transporter. The protein is involved in the transport of microcins B17 and J25, bleomycin, proline-rich antimicrobial peptides, antisense peptide phosphorodiamidate morpholino oligomers, and peptide nucleic acids into the Escherichia coli cytoplasm. The sbmA homologue is found in a variety of bacteria, though the physiological role of the protein is hitherto unknown. In this work, we carried out a functional and structural analysis to determine which amino acids are critical for the transport properties of SbmA. We created a set of 15 site-directed sbmA mutants in which single conserved amino acids were replaced by glycine residues. Our work demonstrated that strains carrying the site-directed mutants V102G, F219G, and E276G had a null phenotype for SbmA transport functions. In contrast, strains carrying the single point mutants W19G, W53G, F60G, S69G, N155G, R190, L233G, A344G, T255G, N308G, and R385G showed transport capacities indistinguishable from those of strains harboring a wild-type sbmA. The strain carrying the Y116G mutant exhibited mixed phenotypic characteristics. We also demonstrated that those sbmA mutants with severely impaired transport capacity showed a dominant negative phenotype. Electron microscopy data and in silico three-dimensional (3D) homology modeling support the idea that SbmA forms a homodimeric complex, closely resembling the membrane-spanning region of the ATP-binding cassette transporter family. Direct mapping of the sbmA single point mutants on the protein surface allowed us to explain the observed phenotypic differences in transport ability.

Macrophage environment turns otherwise MccJ25-resistant Salmonella into sensitive.

BACKGROUND: Microcin J25 (MccJ25) is a plasmid-encoded antibiotic peptide produced by Escherichia coli (E. coli). MccJ25 enters into the sensitive E. coli strains by the outer membrane receptor FhuA and the inner membrane proteins TonB, ExbB, ExbD and SbmA. The resistance of Salmonella enterica serovar Typhimurium (S. Typhimurium) to MccJ25 is attributed to the inability of its FhuA protein to incorporate the antibiotic into the cell. RESULTS: In this work we demonstrate that S. Typhimurium becomes notably susceptible to MccJ25 when replicating within macrophages. In order to determine the possible cause of this phenomenon, we studied the sensitivity of S. Typhimurium to MccJ25 at conditions resembling those of the internal macrophage environment, such as low pH, low magnesium and iron deprivation. We observed that the strain was only sensitive to the antibiotic at low pH, leading us to attribute the bacterial sensitization to this condition. A MccJ25-resistant E. coli strain in which fhuA is deleted was also inhibited by the antibiotic at low pH. Then, we could assume that the MccJ25 sensitivity change observed in both E. coli fhuA and S. Typhimurium is mediated by a MccJ25 uptake independent of the FhuA receptor. Moreover, low pH incubation also sensitized S. Typhimurium to the hydrophobic antibiotic novobiocin, which does not affect enteric bacteria viability because it is unable to penetrate the bacterial outer membrane. This observation supports our hypothesis about low pH producing a modification in the bacterial membrane permeability that allows an unspecific MccJ25 uptake. On the other hand, MccJ25 inhibited S. Typhimurium when cells were preincubated in acidic pH medium and then treated at neutral pH with the antibiotic. CONCLUSIONS: Our results suggest that acidic condition does not alter MccJ25 hydrophobicity but irreversibly modifies bacterial membrane permeability. This would allow an unspecific antibiotic uptake into the cell.From our data it is possible to infer that intracellular pathogenic strains, which are in vitro resistant to MccJ25, could become susceptible ones in vivo. Therefore, the MccJ25 action spectrum would be broader than what in vitro experiments indicate.

Catecholate siderophores protect bacteria from pyochelin toxicity.

BACKGROUND: Bacteria produce small molecule iron chelators, known as siderophores, to facilitate the acquisition of iron from the environment. The synthesis of more than one siderophore and the production of multiple siderophore uptake systems by a single bacterial species are common place. The selective advantages conferred by the multiplicity of siderophore synthesis remains poorly understood. However, there is growing evidence suggesting that siderophores may have other physiological roles besides their involvement in iron acquisition. METHODS AND PRINCIPAL FINDINGS: Here we provide the first report that pyochelin displays antibiotic activity against some bacterial strains. Observation of differential sensitivity to pyochelin against a panel of bacteria provided the first indications that catecholate siderophores, produced by some bacteria, may have roles other than iron acquisition. A pattern emerged where only those strains able to make catecholate-type siderophores were resistant to pyochelin. We were able to associate pyochelin resistance to catecholate production by showing that pyochelin-resistant Escherichia coli became sensitive when biosynthesis of its catecholate siderophore enterobactin was impaired. As expected, supplementation with enterobactin conferred pyochelin resistance to the entE mutant. We observed that pyochelin-induced growth inhibition was independent of iron availability and was prevented by addition of the reducing agent ascorbic acid or by anaerobic incubation. Addition of pyochelin to E. coli increased the levels of reactive oxygen species (ROS) while addition of ascorbic acid or enterobactin reduced them. In contrast, addition of the carboxylate-type siderophore, citrate, did not prevent pyochelin-induced ROS increases and their associated toxicity. CONCLUSIONS: We have shown that the catecholate siderophore enterobactin protects E. coli against the toxic effects of pyochelin by reducing ROS. Thus, it appears that catecholate siderophores can behave as protectors of oxidative stress. These results support the idea that siderophores can have physiological roles aside from those in iron acquisition.

A beverage-specific measure of expectancies for malt liquor: development and initial testing.

Malt liquor (ML) is a unique, high alcohol content beverage marketed to encourage heavy drinking. We developed the Malt Liquor Expectancy Questionnaire (MLEQ), a beverage-specific measure of alcohol expectancies, and examined its association with typical weekly ML use, typical weekly alcohol use, and alcohol problems. Forty positive and 40 negative expectancy items were administered to a sample of 639 young adults who regularly consumed ML. Exploratory and confirmatory factor analyses led to the development of the 30-item MLEQ. The MLEQ consists of two positive (i.e., Social Facilitation and Enjoyment, Enhanced Sexuality) and two negative factors (i.e., Aggression and Negative Consequences; Impairment and Physical Symptoms) that possess good internal consistency, test-retest reliability, and convergent validity. The psychometrically sound MLEQ contributes to the limited research on beverage-specific expectancies and heavy drinking.