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PubMed2005

Substrate uptake tests and quantitative FISH show differences in kinetic growth of bulking and non-bulking activated sludge.

The competition between filaments and floc formers in activated sludge has been historically described using kinetic selection. However, recent studies have suggested that bacterial storage may also be an important factor in microbial selection, since the dynamic nature of substrate flows into wastewater treatment plants elicit transient responses from microorganisms. Respirometry-based kinetic selection should thus be reevaluated by considering cell storage, and a more reliable method should be developed to include bacterial storage in the analysis of growth of filaments and floc formers in activated sludge. In this study, we applied substrate uptake tests combined with metabolic modeling to determine the growth rates, yields and maintenance coefficients of bulking and non-bulking activated sludge developed in lab scale reactors under feast and famine conditions. The results of quantitative fluorescence in situ hybridization (FISH) showed that the filaments Eikelboom Type 1851, Type 021N, and Thiothrix nivea were dominant in bulking sludge, comprising 42.0 % of mixed liquor volatile suspended solids (MLVSS), with 61.6% of the total filament length extending from flocs into bulk solution. Only low levels of Type 1851 filament length (4.9% of MLVSS) occurred in non-bulking sludge, 83.0% of which grew inside the flocs. The kinetic parameters determined from the substrate uptake tests were consistent with those from respirometry and showed that filamentous bulking sludge had lower growth rates and maintenance coefficients than non-bulking sludge. These results provide support for growth kinetic differences in explaining the competitive strategy of filamentous bacteria.

Bacteria↗
PubMed2006

Effect of the applied organic load rate on biodegradable polymer production by mixed microbial cultures in a sequencing batch reactor.

This article studies the operation of a new process for the production of biopolymers (polyhydroxyalkanoates, PHAs) at different applied organic load rates (OLRs). The process is based on the aerobic enrichment of activated sludge to obtain mixed cultures able to store PHAs at high rates and yields. A mixture of acetic, lactic, and propionic acids at different concentrations (in the range 8.5-31.25 gCOD/L) was fed every 2 h in a sequencing batch reactor (SBR). The resulting applied OLR was in the range 8.5-31.25 gCOD/L/day. Even though, as expected, the increase in the OLR caused an increase in biomass concentration (up to about 8.7 g COD/L), it also caused a relevant decrease of maximal polymer production rate. This decrease in polymer production rate was related to the different extent of "feast and famine" conditions, as function of the applied OLR and of the start-up conditions. As a consequence the best performance of the process was obtained at an intermediate OLR (20 gCOD/L/day) where both biomass productivity and PHA storage were high enough. However, at this high OLR the process was unstable and sudden decrease of performance was also observed. The sludge characterized by the highest PHA storage response was investigated by 16S rDNA clone library. The clone library contained sequences mostly from PHA producers (e.g., Alcaligenes and Comamonas genera); however many genera and among them, one of the dominant (Thauera), were never described before in relation to PHA storage response.

Acids, Acyclic↗
PubMed2005

A new approach for modelling simultaneous storage and growth processes for activated sludge systems under aerobic conditions.

By critically evaluating previous models, a new mechanistic model is developed to describe simultaneous storage and growth processes occurring in activated sludge systems under aerobic conditions. Identifiability was considered an important criterion during the model development since it among others helps to increase the realiability and applicability of models to full-scale WWTPs. A second order model was proposed for description of the degradation of the storage products under famine conditions. The model is successfully calibrated by only using OUR data obtained from batch experiments. Calibrations were performed with biomass from full-scale WWTPs in Belgium and Spain. Predictions of the calibrated model were successfully confirmed using off-line PHB measurements, supporting the validity of the model. An iterative experimental design procedure was successfully applied and found to remarkably improve the parameter estimation accuracy for the growth on storage parameters K1 and K2, which used to have large confidence intervals when using standard experiments. The estimated biomass growth yield on substrate (0.58 mgCOD/mgCOD) is quite close to the theoretically expected range for heterotrophic growth. This became possible by properly accounting for the storage process. Moreover, the maximum growth rate was predicted in the range 0.7-1.3 per day. This range, albeit quite lower than the values reported for the growth-based ASM models, is believed to be more realistic. Finally, the new model is expected to better and more mechanistically describe simultaneous storage and growth activities of activated sludge systems and as such could contribute to improved design, operation and control of those systems.

Bacteria, Aerobic↗
PubMedDate not supplied

Human obesity: an evolutionary approach to understanding our bulging waistline.

The unique worldwide spread of the human species and the remarkably long post-reproductive survival show that our genome permits excellent adaptation to vastly different environments. Moreover, the main scourges of later age, namely malignant growths and atherosclerosis, appear in humans later than in shorter-living animals. In recent years, excess weight and obesity have become mass phenomena with a pronounced upward trend in all developed countries. However, despite the detrimental effects of being overweight, these populations live longer than ever, which in part may be explained by the availability of better medical treatment. The prevalence and predicted further spread of obesity can be understood in the light of evolution. In all animal species energy metabolism is asymmetric with energy accumulation ('thrifty genotype') being the necessary condition of survival during hard times. For humans, which are no different to other animals in this respect, this genetic programming was necessary for survival because during the course of history, including the recorded history in the more developed Middle East, Europe or China, there was never a long period of uninterrupted food abundance, whereas famines were regular and frequent. Therefore fat accumulation, when food was available, meant survival at times of shortage, while the possible detrimental effects of overindulgence in food and being overweight expressed in unrealistically old age were irrelevant. It is the central, mostly intra-abdominal fat (in both humans and animals) that is more medically important than the subcutaneous truncal fat, and the accumulation of both types of fat is conditioned by high food consumption; therefore it is a historic novelty for human populations. In contrast, lower-body fat in human females is unique in the animal kingdom: it is much less metabolically active, it is of much lower pathologic significance than central fat, and it is programmed to be mobilized mostly during pregnancy and lactation. In view of all this, norms of desired weight should be based on hard mortality and morbidity statistics and not on theoretical, esthetic or fashion considerations. By this criterion, the upper limit of desirable weight is likely to be body mass index (BMI) 27 or 28, but specified for different populations (sex, race, ethnic origin); moreover, with aging, the detrimental effects of obesity diminish and finally disappear. Risks of other pathologies related to obesity (e.g. diabetes, hypertension and coronary disease) are also population-specific. However, total fatness, measured by BMI, is insufficiently sensitive as a risk factor, and fat distribution (upper-body versus low-body type, as reflected by waist circumference and waist:hip ratio) plays at least as prominent a role. Therefore the detailed norms, not yet available, should take into account both general obesity and fat distribution and be specific for different populations. Since long-term weight loss in adults is rarely achievable, public health measures should be aggressively directed at the prevention of obesity from childhood.

Adipose Tissue↗
PubMed2006

Recent advances in polyhydroxyalkanoate production by mixed aerobic cultures: from the substrate to the final product.

Numerous bacteria have been found to exhibit the capacity for intracellular polyhydroxyalkanoates (PHA) accumulation. Current methods for PHA production at the industrial scale are based on their synthesis from microbial isolates in either their wild form or by recombinant strains. High production costs are associated with these methods; thus, attempts have been made to develop more cost-effective processes. Reducing the cost of the carbon substrates (e.g., through feeding renewable wastes) and increasing the efficiency of production technologies (including both fermentation and downstream extraction and recovery) are two such examples of these attempts. PHA production processes based on mixed microbial cultures are being investigated as a possible technology to decrease production costs, since no sterilization is required and bacteria can adapt quite well to the complex substrates that may be present in waste material. PHA accumulation by mixed cultures has been found under various operational conditions and configurations at both bench-scale and full-scale production. The process known as "feast and famine" or as "aerobic dynamic feeding" seems to have a high potential for PHA production by mixed cultures. Enriched cultures submitted to a transient carbon supply can synthesize PHA at levels comparable to those of pure cultures. Indeed, the intracellular PHA content can reach around 70% of the cell dry weight, suggesting that this process could be competitive with pure culture PHA production when fully developed. Basic and applied research of the PHA production process by mixed cultures has been carried out in the past decade, focusing on areas such as microbial characterization, process configuration, reactor operational strategies, process modeling and control, and polymer characterization. This paper presents a review of the PHA production process with mixed cultures, encompassing the findings reported in the literature as well as our own experimental results in relation to each of these areas.

Bacteria, Aerobic↗
PubMedDate not supplied

Third variable analysis: application to causal sequences among nutrient intake, maternal weight, birthweight, placental weight, and gestation.

We applied a set of procedures, aimed at enhancing the strength of inferences about the direction of causal paths among variables measured at the same time, to foetal and maternal indices recorded at birth and collected for study of the Dutch famine of 1944/5. The analysis of three-variable sets yielded strong inferences about the relations among caloric intake, maternal weight, birthweight, placental weight, and length of gestation. These procedures constitute not only a useful preliminary to the construction of multivariate path models, but produce useful results in their own right.

Birth Weight↗
PubMed2000

Geophagy among primates: adaptive significance and ecological consequences.

We review geophagy, or soil ingestion, in primates. This behaviour is widespread and is presumed to be important to health and nutrition. Primates may engage in geophagy for one or a combination of reasons. Here we present, and make a preliminary assessment of, six nonexclusive hypotheses that may contribute to the prevalence of geophagy. Four hypotheses relate to geophagy in alleviating gastrointestinal disorders or upsets: (1) soils adsorb toxins such as phenolics and secondary metabolites; (2) soil ingestion has an antacid action and adjusts the gut pH; (3) soils act as an antidiarrhoeal agent; and (4) soils counteract the effects of endoparasites. Two hypotheses pertain to geophagy in supplementing minerals and/or elements: (5) soils supplement nutrient-poor diets and (6) soils provide extra iron at high altitudes. In addition to these hypotheses, geophagy may satiate olfactory senses, serve as a famine food and finally may have no function at all. We draw together a large body of information from various sources to assess these hypotheses and suggest some tests to understand the function of geophagy. Our review suggests that primates engage in geophagy for a number of reasons that are nonexclusive. We conclude that mineral supplementation, adsorption of toxins, treatment of diarrhoea and pH adjustment of the gut seem the most plausible reasons why primates engage in geophagy. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1993

An hypothesis for the periodicity of smallpox epidemics as revealed by time series analysis.

Parish registers have been studied by time series analysis to detect smallpox epidemics in England during 1600-1800. Confirmatory evidence was provided by the seasonality of child mortality. A 5-year cycle in smallpox epidemics was detected in medium-sized, rural towns. Consideration of the mathematics of the dynamics of viral diseases suggests that the true interepidemic period where smallpox is endemic should be 2-3 years and it is concluded that, in the towns studied, the disease was not endemic but that the oscillations were established by 5-year cycles of periods of famine associated with high wheat prices. The cross-correlation function between the two cycles shows zero lag and the input-output function shows significant coherence. Another epidemic follows only when a sufficient density of susceptibles has been established by births, so that the cycles become phase-locked. It is predicted that smallpox (i) was endemic in London and other large cities, with 2-3 year epidemics, (ii) was epidemic with a 5-year oscillation in rural towns, (iii) did not reach epidemic proportions in scattered communities.

Birth Rate↗
PubMed2004

Mitochondrial genome single nucleotide polymorphisms and their phenotypes in the Japanese.

Polymorphisms in the human mitochondrial genome have been used for the elucidation of phylogenetic relationships among various ethnic groups. Because analysis by mitochondrial genetics has detected pathogenic mutations causing mitochondrial encephalomyopathy or cardiomyopathy, most of the mitochondrial single nucleotide polymorphisms (mtSNPs) found in control subjects have been regarded as merely normal variants. However, we cannot exclude the possibility that the mitochondrial functional differences among individuals are ascribable at least in part to the mtSNPs of each individual. Human lifespan in ancient history was much shorter than that at the present time. Therefore, it is reasonable to speculate that certain mtSNPs that predispose one toward susceptibility to adult- or elderly-onset diseases, such as Parkinson's disease and Alzheimer's disease, have never been a target for natural selection in the past. Similarly, thrifty mtSNPs that had been advantageous for survival under severe famine or cold climate conditions might turn out to be related to satiation-related diseases, such as diabetes mellitus and obesity. To examine these hypotheses, we have constructed a mtSNP database by sequencing the entire mitochondrial genomes of 672 subjects: 96 in each of seven groups (i.e., centenarians, young obese or non-obese subjects, diabetic patients with or without major vascular involvement, patients with Parkinson's disease, and those with Alzheimer's disease).

Brain↗
PubMed1980

[Development of medical sciences in China].

Three periods or stages can be recognized in the development of medicine in China. The first one, being the indigenous medical practice, has its own philosophical approach and can therefore not simply be combined with Western medicine. The second period, in which medical missionaries introduced modern medicine was still a time of laissez-faire and pestilence. The third stage was ushered in by the liberation in 1949 and is characterized by the fact that the government no longer regards health as the private affair of the individual but as a task for the whole community. A number of endemic and epidemic diseases were conquered mainly through close cooperation between the population and medical workers. Success must be regarded as in an important part due to land reform and the eradication of famine. Further improvement in health care will depend to a great deal on improvement in living standards and a lessening of population pressure. As family planning meets resistance for economic and other reasons, only specific measures by the state can bring about a change in attitude. The progress in preventive measures is matched by advances in the technical aspects of medicine and especially too in medical education.

China↗
PubMed1990

Community health in a rural area of Sudan.

A community survey was conducted in Al awayda village, one of eight villages selected for study in the rural Gezira province of Sudan. The objective of the survey was to identify the main health, social and economic problems of people in rural areas and to set priorities as a first phase in a rural development program. The results showed a high illiteracy rate and poor socioeconomic status aggravated by the drought and famine which affected this area of Africa in the years 1983-85. There was an inadequate safe water supply, poor environmental sanitation and inadequate primary health care services. The major disease problems were malaria, diarrheal diseases and schistosomiasis. The implementation of primary health care services with special emphasis on maternal and child health and health education is a clear need. The impact of Sennar Sugar Agricultural Scheme on this village is also discussed.

Community Health Services↗
PubMed2004

Treatment of dairy effluents in an aerobic granular sludge sequencing batch reactor.

Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15-30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% CODtotal, 80% Ntotal and 67% Ptotal can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l-1 CODdissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.

Aerobiosis↗
PubMed2004

Selection pressure-driven aerobic granulation in a sequencing batch reactor.

In recent years, the research on aerobic granulation has been intensive. So far, almost all aerobic granules can form only in sequencing batch reactors (SBR), while the reason is not yet understood. This paper attempts to review the factors involved in aerobic granulation in SBR, including substrate composition, organic loading rate, hydrodynamic shear force, feast-famine regime, feeding strategy, dissolved oxygen, reactor configuration, solids retention time, cycle time, settling time and exchange ratio. The major selection pressures responsible for aerobic granulation are identified as the settling time and exchange ratio. A concept of the minimal settling velocity of bioparticles is proposed; and it is quantitatively demonstrated that the effects of settling time and exchange ratio on aerobic granulation in SBR can be interpreted and unified on the basis of this concept very well. It appears that the formation and characteristics of aerobic granules can be manipulated through properly adjusting either the settling time or the exchange ratio in SBR. Consequently, theoretical and experimental evidence point to the fact that aerobic granulation is a selection pressure-driven cell-to-cell immobilization process.

Bacteria, Aerobic↗
PubMed2001

Overview of glucose regulation.

Glucose homeokinesis is a remarkable process that provides glucose to the body for energy and a constant source of glucose to the brain while preventing hyperglycemia. The latter leads to excessive glycosylation of proteins, changing their structure and function and eventually affecting every organ system in the body. Despite a variable diet of feast and famine throughout the day, the body maintains strict blood glucose levels through a remarkable network between the pancreas, liver, adipose tissue, muscle, and brain. These interactions and both glucose production and utilization are discussed. Glucose production is governed by the liver, which can generate free glucose from hepatic glycogen stores and de novo through gluconeogenesis. Specific glucose transporters found on every cell of the body administer glucose utilization. Each transporter works with a different serum glucose level. The mechanism of these transporters and the specific glucose cycles are discussed. The purpose of this article is to review glucose regulation; it serves as a reference for the other presentations of this symposium.

Animals↗
PubMed1997

Genetic analysis of mutagenesis in aging Escherichia coli colonies.

Bacteria live in unstructured and structured environments, experiencing feast and famine lifestyles. Bacterial colonies can be viewed as model structured environments. SOS induction and mutagenesis have been observed in aging Escherichia coli colonies, in the absence of exogenous sources of DNA damage. This cAMP-dependent mutagenesis occurring in Resting Organisms in a Structured Environment (ROSE) is unaffected by a umuC mutation and therefore differs from both targeted UV mutagenesis and recA730 (SOS constitutive) untargeted mutagenesis. As a recB mutation has only a minor effect on ROSE mutagenesis it also differs from both adaptive reversion of the lacI33 allele and from iSDR (inducible Stable DNA Replication) mutagenesis. Besides its recA and lexA dependence, ROSE mutagenesis is also uvrB and polA dependent. These genetic requirements are reminiscent of the untargeted mutagenesis in lambda phage observed when unirradiated lambda infects UV-irradiated E. coli. These mutations, which are not observed in aging liquid cultures, accumulate linearly with the age of the colonies. ROSE mutagenesis might offer a good model for bacterial mutagenesis in structured environments such as biofilms and for mutagenesis of quiescent eukaryotic cells.

Bacterial Proteins↗
PubMed2005

A preliminary reconstruction (A.D. 1635-2000) of spring precipitation using oak tree rings in the western Black Sea region of Turkey.

Tree-ring data for Turkey are crucial to the understanding of the climatological effect of drought and rainfall from one era to the next. To this end, the present study reconstructed precipitation patterns in the western Black Sea region of Turkey. Tree-ring widths of oak trees were used to reconstruct March-June precipitation patterns for the years A.D. 1635-2000. According to the findings, during the past four centuries drought events in this region persisted for no more than 2 years, and extreme dry and wet events occurred generally in 1-year intervals. Historical records of droughts in Anatolia and neighboring countries corroborate the data furnished by tree-ring widths to indicate that major droughts and famine events occurred in 1725, 1757, 1887, 1890-1891, 1893-1894 and 1927-1928.

Climate↗
PubMed2004

Combating desertification: building on traditional knowledge systems of the Thar Desert communities.

The Thar Desert of western India is known for its rich and ancient culture system and traditions. The communities have long been part of the Thar Desert ecosystem and have evolved specific strategies to live in harmony with its hostile environment. This culture has provided several miracle plants of immense food and medicinal value to modern civilisation. The ancient rural livelihood knowledge system reflects time-tested techno-scientific knowledge with a proven track record of sustainability, especially during natural hazards like drought and famines. In addition, several of the traditional skills of local communities in arts and crafts, music and instruments have made modern man aware of the art and techniques of sustainably utilising local biological resources and preserving their biodiversity along with using waste products of the forests, without harming the desert ecosystem. Traditional cultural and socio-religious values are fast dwindling under the impact of materialistic approach, industrialisation and development. This paper endeavours to illustrate the need to assist and propagate indigenous rural livelihood systems rather than mindlessly replace or abandon them as a result of state bureaucracies.

Agriculture↗
PubMed2006

Prenatal programming of childhood overweight and obesity.

OBJECTIVE: To review the scientific evidence for prenatal programming of childhood overweight and obesity, and discuss its implications for MCH research, practice, and policy. METHODS: A systematic review of observational studies examining the relationship between prenatal exposures and childhood overweight and obesity was conducted using MOOSE guidelines. The review included literature posted on PubMed and MDConsult and published between January 1975 and December 2005. Prenatal exposures to maternal diabetes, malnutrition, and cigarette smoking were examined, and primary study outcome was childhood overweight or obesity as measured by body mass index (BMI) for children ages 5 to 21. RESULTS: Four of six included studies of prenatal exposure to maternal diabetes found higher prevalence of childhood overweight or obesity among offspring of diabetic mothers, with the highest quality study reporting an odds ratio of adolescent overweight of 1.4 (95% CI 1.0-1.9). The Dutch famine study found that exposure to maternal malnutrition in early, but not late, gestation was associated with increased odds of childhood obesity (OR 1.9, 95% CI 1.5-2.4). All eight included studies of prenatal exposure to maternal smoking showed significantly increased odds of childhood overweight and obesity, with most odds ratios clustering around 1.5 to 2.0. The biological mechanisms mediating these relationships are unknown but may be partially related to programming of insulin, leptin, and glucocorticoid resistance in utero. CONCLUSION: Our review supports prenatal programming of childhood overweight and obesity. MCH research, practice, and policy need to consider the prenatal period a window of opportunity for obesity prevention.

Adolescent↗