Circadian rhythms in microalgae production

Abstract Thesis: Circadian rhythms in microalgae production Lenneke de Winter The sun imposes a daily cycle of light and dark on nearly all organisms. The circadian clock evolved to help organisms program their activities at an appropriate time during this daily cycle. For example, UV sensitive processes, like DNA replication, can be scheduled to occur during the night (Nikaido and Johnson, 2000). In this way, the circadian clock causes rhythms in metabolic, physiological and/or behavioural events (Mittag et al., 2005). These circadian rhythms continue for some period of time following exposure to continuous light (Harding Jr et al., 1981) and have a duration of approximately 24 hours. In microalgae, circadian rhythms were observed in many processes, like nitrogen fixation, chemotaxis, photosynthesis and the cell division cycle (Mittag, 2001), which might affect the production of microalgae. Microalgae biomass can be used as source for potential biofuels, chemicals, materials, foods, feeds and high-value bioactives (Chisti, 2007; Hu et al., 2008; Wijffels and Barbosa, 2010). However, the current production process of microalgae needs to be optimized in order to become economically feasible (Norsker et al., 2011). Researchers focussed on optimizing PBR design (Molina et al., 2001; Morweiser et al., 2010; Sierra et al., 2008), operating strategies (Cuaresma et al., 2011; Morweiser et al., 2010; Olivieri et al., 2014) and microalgae metabolism (Guschina and Harwood, 2006; Klok et al., 2013a), but as of yet did not consider the possible influence of circadian rhythms on microalgae production. Biomass growth rate, biomass yield on light, and the biochemical composition of algal biomass are important factors in the production of microalgae. These factors are likely to be influenced by the day/night cycle and the circadian clock. Therefore, the aim of the work presented in this thesis was to obtain more insight in circadian rhythms in microalgae grown in photobioreactors. In chapter 2 it is described how the green microalgae Neochloris oleoabundans was grown in a photobioreactor operated as a turbidostat under continuous red LED light. Cell division in N. oleoabundans was shown to be under control of the circadian clock, and took place by multiple fission during the natural night. Due to the synchronized cell division, oscillations in biomass yield and composition were observed, despite the continuous red LED light. Synchronization disappeared under continuous white LED light, and therefore it was concluded that a blue light receptor might be involved in triggering synchronous cell division of N. oleoabundans. As biomass composition is also dependent on other culture conditions, the same set-up was used in chapter 3, only this time the culture was grown nitrogen-limited, as this is the most commonly used method for the production of storage components. In this way, it was shown that under nitrogen limitation the circadian clock was still timing cell division to the natural night. However, because of the lower growth rate, two subpopulations were observed which divided alternately every other day. Again, oscillations in biomass composition were observed. Neutral lipids were built up during the day, especially in cells that were arrested in their cell cycle. After having studied the circadian clock under continuous light conditions, a step was made to day/night cycles. Chapter 4 describes a comparison of biomass yield and composition between a synchronized culture under day/night cycles and a randomly dividing culture under continuous white LED light. In this way it was shown that circadian rhythms had a small influence on biomass yield, with biomass yield on light being 10-15% higher in synchronized cultures. Also biomass composition was influenced, as in continuous light starch never had to be spend for respiration during a dark period and therefore starch content remained higher. For the experiments with a day/night cycle, no difference was found between light supplied at constant intensity (block) or light supplied in a more natural way (sine). Therefore, providing light in a block showed to be a good and easy to operate alternative to using sinuses when working with day/night cycles in the laboratory. Chapter 5 takes a closer look at the multiple fission cell cycle of N. oleaobundans. Day/night cycles of different lengths and intensities were studied, as algae are exposed to different day lengths over the course of a year. Maximum growth rate and start of starch synthesis seemed to be regulated by the circadian clock and were scheduled after approximately 6-7 hours from sunrise. Therefore, they were not influenced by day length. However, day length did have an influence on biomass composition. In longer days, more starch was accumulated. The changes in biomass composition could also be correlated to the cell cycle of N. oleoabundans, and therefore knowledge about the timing of cell division showed to be important for the production of biomass with a desired concentration of protein, lipids, carbohydrates or pigments. In chapter 6 the implications of the overall results of this thesis for current research protocols and microalgae processes are discussed. First the occurrence of circadian rhythms in different species of microalgae is discussed, in order to establish the general nature of these rhythms. Based on the findings for N. oleoabundans, it is concluded that more research should be done using day/night cycles, as experiments under constant light are not representative for outdoor microalgae production. Still more knowledge is required on circadian rhythms in microalgae production and therefore some opportunities for future research are presented. Finally, it is discussed how manipulation of circadian rhythms might help to improve future microalgae production. </p

Alternative pediatric metabolic syndrome definitions impact prevalence estimates and socioeconomic gradients

BACKGROUND: There is no consensus regarding the definition of pediatric metabolic syndrome (MetS). This study assessed the impact of alternative definitions on the prevalence, children identified, and association with socioeconomic status (SES). METHODS: Data were from the prospective multigenerational Dutch Lifelines Cohort Study. At baseline, 9754 children participated, and 5085 (52.1%) with average follow-up of 3.0 (SD = 0.75) years were included in the longitudinal analyses; median ages were 12 (IQR = 10-14) and 14 years (IQR = 12-15), respectively. We computed MetS prevalence according to five published definitions and measured the observed proportion of positive agreement. We used logistic regression to assess the SES-MetS association, adjusted for age and sex. Longitudinal models were also adjusted for baseline MetS. RESULTS: MetS prevalence and positive agreement varied between definitions, from 0.7 to 3.0% and from 0.34 (95% CI: 0.28; 0.41) to 0.66 (95% CI: 0.58; 0.75) at baseline, respectively. We consistently found a socioeconomic gradient; in the longitudinal analyses, each additional year of parental education reduced the odds of having MetS by 8% (95% CI: 1%; 14%) to 19% (95% CI: 7%; 30%). CONCLUSIONS: Alternative MetS definitions had differing prevalence estimates and agreed on 50% of the average number of cases. Additionally, regardless of the definition, low SES was a risk factor for MetS. IMPACT: Little is known about the impact of using different definitions of pediatric metabolic syndrome on study results. Our study showed that the choice of pediatric metabolic syndrome definition produces very different prevalence estimates. We also showed that the choice of definition influences the socioeconomic gradient. However, low socioeconomic status was consistently a risk factor for having pediatric metabolic syndrome. In conclusion, studies using different definitions of metabolic syndrome could be reasonably compared when investigating the association with socioeconomic status but not always validly when comparing prevalence studies

Socioeconomic Health Inequalities in Adolescent Metabolic Syndrome and Depression:No Mediation by Parental Depression and Parenting Style

We assessed to what extent parental depression and parenting style mediate the relationships between different measures of parental socioeconomic status (SES) and both depression and metabolic syndrome (MetS) in adolescents, and whether sex moderates these mechanisms. Data were from the prospective multigenerational Dutch Lifelines Cohort Study. Our sample consisted of 1217 adolescents with an average follow-up of 33.3 (SD = 7.33) months and a median baseline age of 13 (IQR:13–14) years. We used structural equation models to assess the direct and indirect effects of SES on baseline and changes at follow-up in both depression and MetS, and to assess moderation by sex. For each additional year of education, continuous MetS scores were 0.098 (95%CI: 0.020; 0.184) units lower at baseline and decreased 0.079 (95%CI: 0.004; 0.158) units at follow-up. No other direct or indirect effects of SES were found, and there was no moderation by sex. Additionally, warmer parenting style was generally associated with more favorable outcome scores. Therefore, improving parenting style may improve health for all adolescents. However, in this study parental depression and parenting style did not account for adolescent socioeconomic health inequalities. This may be partly due to good access to social services within the Netherlands

The role of functional health literacy in long-term treatment outcomes in psychosocial care for adolescents

Although among adolescents with psychosocial problems low health literacy may increase the risk of poor treatment outcomes, the contributing mechanisms within treatment remain unclear. A better understanding of these mechanisms could contribute to improved treatment processes and outcomes. This study aims to examine the relationship between functional health literacy, treatment processes (treatment adherence, learning processes), and treatment outcome (level of psychosocial problems) in adolescents in psychosocial care. We used data from a prospective cohort study among adolescents aged 12-18 (N = 390), collected in four successive measurements: at entry into care, and 3, 12, and 24 months thereafter. We used a mixed effect model to investigate the association between level of functional health literacy (adequate vs. inadequate) and treatment processes (treatment adherence, learning processes) and treatment outcome (level of psychosocial problems). Between adolescents with adequate and inadequate functional health literacy, we found no differences or change over time in adherence or learning processes. The level of psychosocial problems significantly declined over time (β = - 1.70, 95% CI [- 2.72, - 0.69], p = .001) to a similar degree in both groups, though, in all measurements, the level was consistently higher for adolescents with inadequate health literacy. We conclude that health literacy levels did not affect change in treatment processes nor in outcomes of psychosocial treatment. However, the consistently higher level of psychosocial problems among adolescents with inadequate health literacy suggests an unaddressed need in psychosocial care

Diagnosis of Fanconi Anemia: Mutation Analysis by Multiplex Ligation-Dependent Probe Amplification and PCR-Based Sanger Sequencing

Fanconi anemia (FA) is a rare inherited disease characterized by developmental defects, short stature, bone marrow failure, and a high risk of malignancies. FA is heterogeneous: 15 genetic subtypes have been distinguished so far. A clinical diagnosis of FA needs to be confirmed by testing cells for sensitivity to cross-linking agents in a chromosomal breakage test. As a second step, DNA testing can be employed to elucidate the genetic subtype of the patient and to identify the familial mutations. This knowledge allows preimplantation genetic diagnosis (PGD) and enables prenatal DNA testing in future pregnancies. Although simultaneous testing of all FA genes by next generation sequencing will be possible in the near future, this technique will not be available immediately for all laboratories. In addition, in populations with strong founder mutations, a limited test using Sanger sequencing and MLPA will be a cost-effective alternative. We describe a strategy and optimized conditions for the screening of FANCA, FANCB, FANCC, FANCE, FANCF, and FANCG and present the results obtained in a cohort of 54 patients referred to our diagnostic service since 2008. In addition, the follow up with respect to genetic counseling and carrier screening in the families is discussed

Online Hate: From the Far-Right to the ‘Alt-Right’, and from the Margins to the Mainstream

In the 1990s and early 2000s, there was much discussion about the democratic and anti-democratic implications of the Internet. The latter particularly focused on the ways in which the far-right were using the Internet to spread hate and recruit members. Despite this common assumption, the American far-right did not harness the Internet quickly, effectively or widely. More recently, however, they have experienced a resurgence and mainstreaming, benefitting greatly from social media. This chapter examines the history of their use of the Internet with respect to: (1) how this developed in response to political changes and emerging technologies; (2) how it reflected and changed the status of such movements and their brand of hate; and (3) the relationship between online activity and traditional methods of communication