Accumulation and degradation of polyphosphate in Acinetobacter sp.

Biological phosphate removal from waste water is a biotechnological alternative to chemical phosphorus precipitation. This process is obtained by recycling the sludge through anaerobic and aerobic zones. In the anaerobic parts phosphate is released by the sludge and during anaerobiosis phosphate is taken up. Biological phosphate removal is dependent on the enrichment of activated sludge with polyphosphate accumulating Acinetobacter . Like activated sludge, pure cultures of strictly aerobic Acinetobacter sp. absorbe phosphate (up to 100 mg phosphorus per g dry biomass) during aerobic conditions and release it anaerobically. The aim of this study was to gather knowledge on the uptake and release of phosphate by Acinetobacter and the metabolic functions of polyphosphate.The accumulation of polyphosphate by pure cultures of Acinetobacter strain 210A depended on the presence of an intra- or extracellular energy source (chapter 2). The highest amount of polyphosphate was found in cells in which energy supply was not limited, namely at low growth rates under sulphur limitation, and in the stationary phase of growth when either the nitrogen or the sulphur source was depleted. Accumulation of polyphosphate was also possible during endogenous respiration. When this respiration was blocked with KCN the phosphate uptake stopped, while the inhibition of the protein synthesis with streptomycin enhanced the accumulation of phosphate, which indicated the competition between protein synthesis and polyphosphate synthesis for energy. There was a pronounced effect of the temperature on phosphorus accumulation but this effect varied from strain to strain.The role and behaviour of cations in the accumulation and release of phosphate was studied (chapter 3). PO 43-was released together with 1.8 protons. Mg 2+appeared to be the most important counterion of polyphosphate in Acinetobacter strain 210A. It was released and taken up simultaneously with phosphate. Mg 2+was not an essential polyphosphate counterion. If Mg 2+was depleted, stationary cultures of Acinetobacter strain 210A took up the same amount of phosphate with Ca 2+as the most important counterion. In the presence of Mg 2+stationary cultures did not need Ca 2+for their phosphate absorption, but the presence of K +seemed to be crucial for this process, although this cation did not play a quantitatively important role as a polyphosphate counterion. In addition, the influx and efflux of K +was independent of phosphate uptake and release. Continuous cultivation at low growth rates under K +-limitation did not result in polyphosphate accumulation, while under substrate or Mg 2+- limitation large amounts of polyphosphate were present in the cells. The same effect was found in activated sludge. 5 mg K +per litre was needed for a satisfactory biological phosphate removal in the aerobic zone of a wastewater treatment plant. Granules of Mgpolyphosphate in Acinetobacter strain 210A could serve as a Mg 2+-reserve. Cells with these granules were able to grow in a medium free of Mg 2+, whereas cells without granules were not, they only grew in the presence of extracellular Mg 2+. Polyphosphate in cell-free extracts of Acinetobacter strain 210A could be degraded by the enzymes polyphosphatase or polyphosphate:AMP phosphotransferase (chapters 4 and 6). Polyphosphate glucokinase, polyphosphate dependent NAD-kinase and polyphosphatekinase were not detectable. Polyphosphate:AMP phosphotransferase was also found in Acinetobacter strain B8, but not in Acinetobacter strain P, which contained only polyphosphatekinase. Both strains were able to accumulate large amounts of polyphosphate. In strains that cannot accumulate this biopolymer, no or very small activities of polyphosphatekinase and polyphosphate: AMP phosphotransferase were found. All strains showed activities of adenylate kinase. It was demonstrated that by the combined action of polyphosphate:AMP phosphotransferase and adenylate kinase a continuous regeneration of ATP from AMP or ADP was possible as long as polyphosphate was present. Polyphosphate:AMP phosphotransferase could use native and synthetic polyphosphate as substrate and showed a maximum activity at a pH of 8.5. Its activity was stimulated by (NH 4 ) 2 SO 4 , the K m for AMP appeared to be 0.6 mM, and V max was 60 nmol.min -1.mg -1protein. Polyphosphatase in cell-free extracts of strain 210A was able to hydrolyse native polyphosphate and synthetic Mg-polyphosphate. The K- and Na-form, however, were not degraded. The activities of polyphosphate:AMP phosphotransferase and adenylate kinase in activated sludge correlated well with the ability of the sludge to remove phosphate biologically from waste water.Degradation of polyphosphate invivo in Acinetobacter strain 210A occurred if the energy supply in the cell was stopped, for example under anaerobiosis or in the presence of KCN, α-dinitrophenol or N-N'-dicyclohexylcarbodiimid (chapter 5). The degradation and synthesis of polyphosphate was dependent on the ATP concentration in the cells. Lower ATP concentrations caused a faster phosphate release. This release was stimulated by alcohols. The transmembrane protongradient seemed to play an important role in the anaerobic energy metabolism of this strictly aerobic bacterium. Addition of α-dinitrophenol, a protonionophore, decreased the cellular ATP concentration and stimulated the polyphosphate degradation. The role of polyphosphate as an energy reserve invivo has been demonstrated by experiments in which five strains were incubated anaerobically. Cells of Acinetobacter strains 210A and B8, which were able to accumulate polyphosphate, released large amounts of ortho-phosphate anaerobically and contained high levels of ATP. Cells of two other strains of Acinetobacter and one strain of Pseudomonas which didn't accumulate polyphosphate, showed a much smaller release of phosphate and contained only low ATP concentrations. Cells of strain 210A cultivated under phosphorus limitation or at 350C did not contain detectable amounts of polyphosphate. As a result their ATP level was low and they released only small or negligible amounts of phosphate under anaerobic conditions.Mg-polyphosphate in Acinetobacter sp. is a multifunctional compound. It can serve as: (1) an energy reserve if it is degraded by a reaction with AMP, catalyzed by polyphosphate: AMP phosphotransferase, (2) a phosphorus reserve if it is hydrolyzed by polyphosphatase, and (3) a Mg 2+reserve whereby Mg 2+can be replaced by Ca 2+as a counterion. The most important role of polyphosphate in wastewater treatment plants with biological phosphate removal, and probably also in natural environments, is its use as an energy reserve to sustain temporary anaerobiosis. This property might explain the enrichment of activated sludge subjected to alternating anaerobic and aerobic conditions with polyphosphate accumulating Acinetobacter sp.

PIAAC Numeracy Task Complexity Schema: Factors that impact on item difficulty

This paper describes some lessons learned from international adult numeracy assessments that can help in understanding the challenges that people, including both adults and school students, have when solving numeracy tasks and their levels of performance on functional mathematical problems. The paper presents a theoretical schema of five factors that predict, separately and in interaction, the complexity or level of difficulty of mathematically-related assessment tasks, including tasks that incorporate texts and require literacy or reading skills, which are very common in adults\u27 lives. The model was originally developed as part of the development of the Adult Literacy and LifeSkills survey in the mid \u2790s, but later adapted and effectively used within the Programme for the International Assessment of Adult Competencies (PIAAC), a.k.a. OECD Survey of Adult Skills. The five complexity factors described in the model are grouped into two factors addressing mainly textual aspects of tasks, and three factors addressing the mathematical aspects of tasks. These factors can assist test developers, researchers and educators in predicting task difficulty and in targeting the development of items and tasks to more efficiently cover the range of student performance and skill levels

Corrigendum to: Associations between illness cognitions and health-related quality of life in the first year after diagnosis of amyotrophic lateral sclerosis (vol 132, 109974, 2020)

The authors regret that in the original published article the first and surnames for two authors were presented in the incorrect order and should be swapped around. The correct names for the second and fifth authors are M.W.M. Post and J.M.A. Visser-Meily respectively. The authors would like to apologise for any inconvenience caused

Associations between illness cognitions and health-related quality of life in the first year after diagnosis of amyotrophic lateral sclerosis

Objective: To describe illness cognitions among patients with amyotrophic lateral sclerosis (ALS), to study crosssectional associations between illness cognitions and health-related quality of life (HRQoL) and to study the predictive value of illness cognitions measured shortly after the diagnosis for HRQoL at follow-up. Methods: Prospective longitudinal design. We administered Self-report questionnaires at study onset (n = 72) and follow-up (n = 48). Median follow-up period was 10.0 months. At baseline median ALS Functional Rating Scale-Revised was 43, median time since onset of symptoms was 13.6 months, 79% of patients presented with spinal onset. Illness cognitions Helplessness, Acceptance and Disease Benefits were measured with the Illness Cognitions Questionnaire (ICQ) and HRQoL with the ALS Assessment Questionnaire (ALSAQ-40). Correlational and regression analyses were used. Results: Patients experienced more Helplessness at follow-up. We found no significant changes in Acceptance or Disease Benefits at follow-up. In cross-sectional analyses, Helplessness was independently related to worse HRQoL at baseline (beta = 0.44; p =.001) and Acceptance and Disease Benefits were independently related to worse HRQoL at follow-up (beta = -0.17, p =.045) and (beta = -0.186, p =.03 respectively). Longitudinal analyses showed that, adjusted for disease severity at baseline, Helplessness at baseline was a predictor of worse HRQoL at follow-up (beta = 0.43; p =.006). None of the illness cognitions were a significant predictor of HRQoL with adjustment for baseline HRQoL. Conclusion: Helplessness was independently associated with HRQoL in the cross-sectional and longitudinal analyses. These results can help us identify patients shortly after diagnosis who might benefit from psychological interventions

Participation and autonomy in the first 10 months after diagnosis of ALS:a longitudinal study

Introduction: More insight is needed into participation in daily activities and autonomy among patients with amyotrophic lateral sclerosis (ALS). Aims of this study were (1) to describe the course of participation restrictions and autonomy in participation during the first 10 months after diagnosis; (2) to study the influence of the rate of ALS progression on the course of participation. Methods: Secondary analysis of data from the longitudinal multicenter FACTS-2-ALS study. Self-report questionnaires were administered at inclusion (T0; n = 71), at 4 months (T1), 7 months (T2), 10 months (T3) after inclusion. Median duration of follow-up was 10.0 months. Participation restrictions were assessed using the sum of the Mobility Range and Social Behavior subscales of the Sickness Impact profile-68 (SIPSOC). Autonomy in participation was assessed using the Impact on Participation and Autonomy (IPA) Questionnaire. Fast disease progression was defined as an increase of 1.1 points per month or more on the ALS Functional Rating Scale. Results: Patients reported participation restrictions in all subscales while having mild physical limitations. There was a decrease of participation over time (restrictions and autonomy). This decrease was greatest in patients with fast disease progression. Disease progression negatively influenced movement-related participation more than social interaction domains. Rate of disease progression was more strongly related to SIPSOC scores compared to IPA scores. Discussion: Preserving participation may be an important determinant of quality of care for patients with ALS. Rate of progression of the disease should be taken into account as it was found to be significantly associated with the level of participation

Biofuel production from acid-impregnated willow and switchgrass

As part of a broader technical and economic feasibility study, we studied production of bioethanol from two types of lignocellulosic biomass by way of concentrated acid impregnation at low temperature. Willow chips and switchgrass were submitted to various impregnation techniques with concentrated sulfuric acid at varying acid: biomass ratios and impregnation times. Goal of the experiments was to investigate the technical feasibility of concentrated acid pretreatment technology as part of an industrial process that employs recycling of acid through biological means. Experimental results showed that significant amounts of fermentable sugars including glucose (up to 78 f max. obtainable glucose) and xylose can be obtained by relatively simple impregnation techniques at room temperature. Fermentation of willow-derived hydrolysates with S. Cerevisiae yielded 0.45 - 0.49 g ethanol/g glucose. Ethanol production rates however were 38 ower compared to standard glucose fermentation, prompting the need for further optimization to reduce the formation of acetic acid and furfural, two fermentation inhibitors. Novel impregnation techniques, including employment of sulfur trioxide, were also investigated but require more work to assess technical feasibilit