Expanding the role of FurA as essential global regulator in cyanobacteria

In the nitrogen-fixing heterocyst-forming cyanobacterium Anabaena sp. PCC 7120, the ferric uptake regulator FurA plays a global regulatory role. Failures to eliminate wild-type copies of furA gene from the polyploid genome suggest essential functions. In the present study, we developed a selectively regulated furA expression system by the replacement of furA promoter in the Anabaena sp. chromosomes with the Co2+/Zn2+ inducible coaT promoter from Synechocystis sp. PCC 6803. By removing Co2+ and Zn2+ from the medium and shutting off furA expression, we showed that FurA was absolutely required for cyanobacterial growth. RNA-seq based comparative transcriptome analyses of the furA-turning off strain and its parental wild-type in conjunction with subsequent electrophoretic mobility shift assays and semi-quantitative RT-PCR were carried out in order to identify direct transcriptional targets and unravel new biological roles of FurA. The results of such approaches led us to identify 15 novel direct iron-dependent transcriptional targets belonging to different functional categories including detoxification and defences against oxidative stress, phycobilisome degradation, chlorophyll catabolism and programmed cell death, light sensing and response, heterocyst differentiation, exopolysaccharide biosynthesis, among others. Our analyses evidence novel interactions in the complex regulatory network orchestrated by FurA in cyanobacteria

Effects of benzene and several pharmaceuticals on the growth and microcystin production in Microcystis ruginosa PCC 7806

Currently, the presence of several pharmaceuticals and other organic compounds called ‘emerging’ contaminants has increased in water bodies. These compounds do not need to persist in the environment to cause negative effects because they are continuously introduced. Hence, assessing the effects of these compounds on aquatic ecosystems is essential. Therefore, the aim of the present study was to analyse the effects of several emerging contaminants (ibuprofen, atenolol, diclofenac and paracetamol) and benzene on Microcystis aeruginosa PCC 7806 growth and toxicity. For this purpose, the growth and intracellular microcystin concentration in M. aeruginosa PCC 7806 were measured in presence of the four emerging contaminants and benzene. The growth rate was estimated by chlorophyll a concentration, and no relevant changes were found. Changes in the expression of the operon mcy were examined by semi-quantitative RT-PCR. Intracellular microcystin production was determined using a MicroCystest¿R kit, and no changes were observed compared to control cells. Thus, the tested concentrations of the contaminants analysed in this study do not have a significant effect on microcystin production in this strain under laboratory conditions

Variation in the synthesis of microcystin in response to saline and osmotic stress in Microcystis ruginosa PCC7806

The growth and synthesis of microcystin in Microcystis aeruginosa PCC7806 was studied in cells grown in the presence of NaCl or with sucrose. The saline stress caused a decrease in the transcript levels of mcyD, one of the genes involved in microcystin synthesis, which was correlated with a decrease in the content of microcystin-LR in the cells. The cells treated with sucrose also had reduced levels of mcyD transcripts and contents of microcystin-LR

Validation of metabolic syndrome using medical records in the SUN cohort

The objective of this study was to evaluate the validity of self reported criteria of Metabolic Syndrome (MS) in the SUN (Seguimiento Universidad de Navarra) cohort using their medical records as the gold standard. METHODS: We selected 336 participants and we obtained MS related data according to Adult Treatment Panel III (ATP III) and International Diabetes Federation (IDF). Then we compared information on the self reported diagnosis of MS and MS diagnosed in their medical records. We calculated the proportion of confirmed MS, the proportion of confirmed non-MS and the intraclass correlation coefficients for each component of the MS. RESULTS: From those 336 selected participants, we obtained sufficient data in 172 participants to confirm or reject MS using ATP III criteria. The proportion of confirmed MS was 91.2% (95% CI: 80.7- 97.1) and the proportion of confirmed non-MS was 92.2% (95% CI: 85.7-96.4) using ATP III criteria. The proportion of confirmed MS using IDF criteria was 100% (95% CI: 87.2-100) and the proportion of confirmed non-MS was 97.1% (95% CI: 85.1-99.9). Kappa Index was 0.82 in the group diagnosed by ATP III criteria and 0.97 in the group diagnosed by IDF criteria. Intraclass correlation coefficients for the different component of MS were: 0.93 (IC 95%:0.91- 0.95) for BMI; 0.96 (IC 95%: 0.93-0.98) for waist circumference; 0.75 (IC 95%: 0.66-0.82) for fasting glucose; 0.50 (IC 95%:0.35-0.639) for HDL cholesterol; 0.78 (IC 95%: 0.70-0.84) for triglycerides; 0.49 (IC 95%:0.34-0.61) for systolic blood pressure and 0.55 (IC 95%: 0.41-0.65) for diastolic blood pressure. CONCLUSIONS: Self-reported MS based on self reported components of the SM in a Spanish cohort of university graduates was sufficiently valid as to be used in epidemiological studies

Prospective study of changes in sugar-sweetened beverages consumption and incidence of metabolic syndrome and its components

The incidence of the metabolic syndrome (MetS) is increasing and lifestyle behaviours may play a role. The aim of the present study was to prospectively assess the association between changes in the consumption of sugar-sweetened beverages (SSB) and the incidence of the MetS and its components in a Spanish cohort of university graduates. We included 8157 participants initially free of the MetS and followed up during at least 6 years. SSB consumption was collected by a FFQ previously validated in Spain. The change in SSB consumption was calculated as the difference between SSB consumption at a 6-year follow-up and baseline consumption. The MetS was defined according to the International Diabetes Federation and the American Heart Association/National Heart, Lung, and Blood Institute's new definition of the MetS that had harmonised previous definitions. The associations between changes in SSB intake and the MetS were examined using multiple logistic regression. We observed 361 incident cases of the MetS. Participants who increased their consumption of SSB (upper v. lower quintile) had a significantly higher risk of developing the MetS (adjusted OR 2·2, 95 % CI 1·4, 3·5; P for trend = 0·003). Similarly, they presented a significantly higher risk of developing high blood pressure (adjusted OR 1·6, 95 % CI 1·3, 2·1), central obesity (adjusted OR 2·3, 95 % CI 1·9, 2·7), hypertriacylglycerolaemia (adjusted OR 1·7, 95 % CI 1·1, 2·6) or impaired fasting glucose (adjusted OR 1·6, 95 % CI 1·1, 2·2). In conclusion, an increase in SSB consumption was associated with a higher risk of developing the MetS and other metabolic disorders after 6 years of follow-up in a Mediterranean cohort of university graduates

Dietary α‐Linolenic Acid, Marine ω‐3 Fatty Acids, and Mortality in a Population With High Fish Consumption: Findings From the PREvención con DIeta MEDiterránea (PREDIMED) Study

Background: Epidemiological evidence suggests a cardioprotective role of α‐linolenic acid (ALA), a plant‐derived ω‐3 fatty acid. It is unclear whether ALA is beneficial in a background of high marine ω‐3 fatty acids (long‐chain n‐3 polyunsaturated fatty acids) intake. In persons at high cardiovascular risk from Spain, a country in which fish consumption is customarily high, we investigated whether meeting the International Society for the Study of Fatty Acids and Lipids recommendation for dietary ALA (0.7% of total energy) at baseline was related to all‐cause and cardiovascular disease mortality. We also examined the effect of meeting the society's recommendation for long‐chain n‐3 polyunsaturated fatty acids (≥500 mg/day). Methods and Results: We longitudinally evaluated 7202 participants in the PREvención con DIeta MEDiterránea (PREDIMED) trial. Multivariable‐adjusted Cox regression models were fitted to estimate hazard ratios. ALA intake correlated to walnut consumption (r=0.94). During a 5.9‐y follow‐up, 431 deaths occurred (104 cardiovascular disease, 55 coronary heart disease, 32 sudden cardiac death, 25 stroke). The hazard ratios for meeting ALA recommendation (n=1615, 22.4%) were 0.72 (95% CI 0.56–0.92) for all‐cause mortality and 0.95 (95% CI 0.58–1.57) for fatal cardiovascular disease. The hazard ratios for meeting the recommendation for long‐chain n‐3 polyunsaturated fatty acids (n=5452, 75.7%) were 0.84 (95% CI 0.67–1.05) for all‐cause mortality, 0.61 (95% CI 0.39–0.96) for fatal cardiovascular disease, 0.54 (95% CI 0.29–0.99) for fatal coronary heart disease, and 0.49 (95% CI 0.22–1.01) for sudden cardiac death. The highest reduction in all‐cause mortality occurred in participants meeting both recommendations (hazard ratio 0.63 [95% CI 0.45–0.87]). Conclusions: In participants without prior cardiovascular disease and high fish consumption, dietary ALA, supplied mainly by walnuts and olive oil, relates inversely to all‐cause mortality, whereas protection from cardiac mortality is limited to fish‐derived long‐chain n‐3 polyunsaturated fatty acids. Clinical Trial Registration URL: http://www.Controlled-trials.com/. Unique identifier: ISRCTN35739639

gamma-Lindane increases microcystin synthesis in microcystis aeruginosa PCC7806

HCH factories, and the waste dumpsites associated to its production, have become a global environmental concern, and their runoff could pollute ground and surface waters with high levels of the pollutant. In this study, the influence of lindane (¿-HCH) on microcystin production has been investigated in Microcystis aeruginosa PCC7806. This toxic cyanobacterium is highly tolerant to ¿-lindane (20 mg/L), and produces more toxin (microcystin) in the presence of the pollutant. Microcystis degrades ¿-lindane and presence of ¿-lindane induces genes involved in its own degradation (nirA). RT-PCRsq has been used to monitor changes in levels of transcripts encoded by the mcy operon (mcyD, mcyH and mcyJ), responsible for the microcystin synthesis machinery, as well as other genes involved in its transcriptional regulation, such as ntcA and fur family members. The presence of lindane in the culture media induces mcyD expression, as well as ntcA gene transcription, while other genes, such as mcyH, (putative ABC transporter), are downregulated. The amount of microcystin found in the cells and the culture media is higher when M. aeruginosa is treated with ¿-lindane than in control cells. The results\ suggest that in a lindane polluted environment, Microcystis toxic strains may enhance their microcystin synthesis

2-oxoglutarate enhances NtcA binding activity to promoter regions of the microcystin synthesis gene cluster

The binding affinity of NtcA towards promoter regions of the microcystin gene cluster from Microcystis aeruginosa PCC 7806 has been analyzed by band-shift assay (EMSA). The key nitrogen transcriptional regulator exhibits affinity for two fragments of the bidirectional mcyDA promoter, as well as for promoter regions of mcyE and mcyH. The presence of 2-oxoglutarate increased by 2.5 fold the affinity of NtcA for the mcyA promoter region. The 2-oxoglutarate effect peaked at 0.8 mM, a physiological concentration for this compound under nitrogen-limiting conditions. The results suggest that the 2-oxoglutarate level, as a signal of the C to N balance of the cells, regulates the microcystin gene cluster. © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.This work was funded by the Spanish Ministry of Education and Science (BFU2006-03454 and BFU2009-07424).Peer Reviewe

Nut consumption and 5-y all-cause mortality in a Mediterranean cohort: The SUN project

10.1016/j.nut.2014.02.018Objective: The aim of this study was to assess the association between nut consumption and all-cause mortality after 5-y follow-up in a Spanish cohort. Methods: The SUN (Seguimiento Universidad de Navarra, University of Navarra Follow-up) project is a prospective cohort study, formed by Spanish university graduates. Information is gathered by mailed questionnaires collected biennially. In all, 17 184 participants were followed for up to 5 y. Baseline nut consumption was collected by self-reported data, using a validated 136-item semi-quantitative food frequency questionnaire. Information on mortality was collected by permanent contact with the SUN participants and their families, postal authorities, and the National Death Index. The association between baseline nut consumption and all-cause mortality was assessed using Cox proportional hazards models to adjust for potential confounding. Baseline nut consumption was categorized in two ways. In a first analysis energy-adjusted quintiles of nut consumption (measured in g/d) were used. To adjust for total energy intake the residuals method was used. In a second analysis, participants were categorized into four groups according to pre-established categories of nut consumption (servings/d or servings/wk). Both analyses were adjusted for potential confounding factors. Results: Participants who consumed nuts =2/wk had a 56% lower risk for all-cause mortality than those who never or almost never consumed nuts (adjusted hazard ratio, 0.44; 95% confidence intervals, 0.23-0.86). Conclusion: Nut consumption was significantly associated with a reduced risk for all-cause mortality after the first 5 y of follow-up in the SUN project

Microcystin-LR Binds Iron, and Iron Promotes Self-Assembly

The microcystin-producing Microcystis aeruginosa PCC 7806 and its close strain, the nonproducing Microcystis aeruginosa PCC 7005, grow similarly in the presence of 17 μM iron. Under severe iron deficient conditions (0.05 μM), the toxigenic strain grows slightly less than in iron-replete conditions, while the nonproducing microcystin strain is not able to grow. Isothermal titration calorimetry performed at cyanobacterial cytosol or meaningful environmental pHs values shows a microcystin-LR dissociaton constant for Fe and Fe of 2.4 μM. Using atomic force microscopy, 40% of microcystin-LR dimers were observed, and the presence of iron promoted its oligomerization up to six units. Microcystin-LR binds also Mo, Cu, and Mn. Polymeric microcystin binding iron may be related with a toxic cell colony advantage, providing enhanced iron bioavailability and perhaps affecting the structure of the gelatinous sheath. Inside cells, with microcystin implicated in the fitness of the photosynthetic machinery under stress conditions, the toxin would be involved in avoiding metal-dependent Fenton reactions when photooxidation causes disassembly of the iron-rich photosystems. Additionally, it could be hypothesized that polymerization-depolymerization dynamics may be an additional signal that could trigger changes (for example, in the binding of microcystin to proteins).Peer Reviewe