Starvation Phase Research Articles

Use of electronic nose technology to measure soil microbial activity through biogenic volatile organic compounds and gases release

Gas and volatile organic compounds (VOCs) release in soil is known to be linked to microbial activity and can differently affect the life of organisms in soil. Electronic noses (E-noses) are sensing devices composed of sensor arrays able to measure and monitor gases and VOCs in air. This is the first report on the use of such a sensing device to measure specifically microbial activity in soil. In the present study, γ-irradiated sterilised soil was inoculated with Pseudomonas fluorescens. To be sure for a rapid microbial growth and activity, two pulses of nutrient solution with organic and inorganic C, N, P and S sources were added to soil and the resulting microcosms were incubated for 23 d. During the incubation, respiration and enzyme activities of acid phosphatase, β-glucosidase, fluorescein diacetate hydrolase and protease, were measured, and microbial growth as global biomass of vital cells based on substrate-induced respiration (SIR-C mic) and enumeration of viable and culturable cells by means of dilution plate counts (CFU) were also monitored. Concurrently, VOCs and/or gas evolution in the headspace of the soil microcosms were measured through the E-nose, upon their adsorption on quartz crystal microbalances (QCMs) comprising the sensory device. The E-nose typically generated an odorant image ( olfactory fingerprint) representative of the analysed samples (soils) and resulting from the concurrent perception of all or most of the analytes in headspace, as it commonly happens when several selective but not specific sensors are used together (array). The basic hypothesis of this study was that different soil ecosystems expressing distinct microbial metabolic activities, tested through respiration and enzyme activities, might generate different olfactory fingerprints in headspace. Furthermore, the possibility to detect several substances at the same time, released from the soil ecosystems, possibly deriving from both abiotic and biotic (microbial metabolism) processes provides an “odorant image” representative of the whole ecosystem under study. The E-nose here used succeeded in discriminating between inoculated and non-inoculated ecosystems and in distinguishing different metabolic and growth phases of the inoculated bacteria during incubation. Specifically, E-nose responses were proved highly and significantly correlated with all hydrolytic activities linked to the mobilisation of nutrients from soil organic matter and their cycling, with CO 2 fluxes (respiration and presumed heterotrophic fixation) and with P. fluorescens population dynamics during exponential, stationary and starvation phases measured by SIR-C mic and CFUs. Interestingly, the E-nose successfully detected soil microbial activity stimulated by nutrient supply, even though none of the catalytic activities tested directly produced VOCs and/or gases. The E-nose technology was then proved able to supply a real holistic image of microbial activity in the entire gnotobiotic and axenic soil ecosystems.

RET Modulates Cell Adhesion via Its Cleavage by Caspase in Sympathetic Neurons

RET is a tyrosine kinase receptor involved in numerous cellular mechanisms including proliferation, neuronal navigation, migration, and differentiation upon binding with glial cell derived neurotrophic factor family ligands. RET is an atypical tyrosine kinase receptor containing four cadherin domains in its extracellular part. Furthermore, it has been shown to act as a dependence receptor. Such a receptor is active in the absence of ligand, triggering apoptosis through a mechanism that requires receptor intracellular caspase cleavage. However, different data suggest that RET is not always associated with the cell death/survival balance but rather provides positional information. We demonstrate here that caspase cleavage of RET is involved in the regulation of adhesion in sympathetic neurons. The cleavage of RET generates an N-terminal truncated fragment that functions as a cadherin accessory protein, modifying cadherin environment and potentiating cadherin-mediated cell aggregation. Thus, the caspase cleavage of RET generates two RET fragments: one intracellular domain that can trigger cell death in apoptotic permissive settings, and one membrane-anchored ectodomain with cadherin accessory activity. We propose that this latter function may notably be important for the adequate development of the superior cervical ganglion.

Implications of Growth and Starvation Conditions in Bacterial Adhesion and Transport

Biofouling is synonymous with unwanted biofilms and leads to problems ranging from efficiency and resource loss to health risks. While a number of bacterial properties including biomass concentration and hydrophobicity are considered critical to biofilm development and bacterial adhesion, the variations in these properties under growth and starvation conditions are not very well known. Here, we describe the trends in these properties for four Gram-negative bacteria under growth and extended starvation conditions. A convenient and frequently-used laboratory assay, the microbial adhesion to hydrocarbons (MATH) test, was used to determine the microbial hydrophobicity based on the partitioning of cells at an aqueous-hydrocarbon interface. The bacteria tested exhibited a plateau in hydrophobicity values during the stationary growth phase and longer starvation durations (≥10 days). Starved cultures had higher hydrophobicity and lower cell sizes than growth cultures. Interestingly, hydrocarbon exposure led to an increase in cell size for starved cells as compared to control cultures, while cells under growth conditions did not show significant size changes due to hydrocarbon presence. Cells starved for short durations (up to 7–10 days) exhibited significant variations in microbial hydrophobicity, cell size, and biomass concentration (total proteins and optical density). These results show the importance of studying the bacterial properties as a function of growth and starvation phase for cell adhesion in the context of biofilm formation and biofouling.

Bacterial Viability in Starved and Revitalized Biofilms: Comparison of Viability Staining and Direct Culture

Objectives The aim of this study was to enumerate viable bacteria at different growth stages of a multispecies oral biofilm and to compare results obtained with the LIVE/DEAD BacLight Kit (Molecular Probes, Eugene, OR) with those from culturing and plate counting (colony-forming unit counts [CFUs]). Methods The multispecies biofilm was grown from plaque bacteria on collagen-coated hydroxyapatite disks in brain-heart infusion broth for 3 weeks (phase І) with a weekly addition of new nutrients. This was followed by a 9-week nutrient-deprivation phase (phase ІІ); after which, the biofilm was reactived again by weekly additions of fresh BHI medium for 4 weeks (phase ІІІ). The number and proportion of live bacteria in biofilm was assessed by culturing and by confocal laser scanning microscopy using a LIVE/DEAD viability stain throughout the experiment. Results The CFU counts dropped more than four logarithmic steps during phase ІІ. However, viability staining by LIVE/DEAD stain indicated only a 25% drop in viability. The CFU counts increased during phase III, but it took 4 weeks for them to return close to the original CFU numbers. Cell viability, as indicated by the staining, improved from 75% close to the original 100%. Conclusions Bacteria in the multispecies biofilm grown under nutrient deprivation became viable but nonculturable but could be brought back to a culturable state after reestablishing sufficient access to nutrients. The results indicate that viability staining better reflected true viability of the biofilm bacteria than culturing during the long starvation phase. The result of this study may have an impact on the interpretation of cultural studies on root canal microbiology/biofilms in vivo.

Effects of nitrogen source and concentration on biomass and oil production of a Scenedesmus rubescens like microalga

This investigation examined the effects of nitrogen source and concentration on the ash free dry biomass (AFDB) and oil accumulation and productivity of a Scenedesmusrubescens like alga cultivated in indoor photo-bioreactors and outdoor raceway ponds. Among the nitrogen sources ((NH4)2CO3, urea, NaNO3, urea and NaNO3 mixture), the algae fed with the mixture of urea-N and NaNO3-N had the highest AFDB productivity of 0.539±0.040 g/L/d and the content of fatty acid methyl esters (FAME) (%) fed with (NH4)2CO3-N increased continuously for 17 days and reached 42.94±2.05% in the indoor photo-bioreactors. The content of C18 series (as % of total FAME) was high in all the treatments of nitrogen sources. The algae fed with (NH4)2CO3-N had the highest FAME productivity of 0.133 g/L/d (P<0.001). The effect of ammonia concentration on the AFDB and FAME productivity was also studied during the 20-day cultivation in the outdoor raceway cultivation system. The mean FAME of the algae cultivated in the ammonia concentration of 1.0-1.5 mg/L were the highest (0.556±0.112 g/m2/d) (P<0.001). The total Kjeldahl nitrogen (TKN) in the algae and cultivation water decreased but the FAME content (%) of the algae increased during the nitrogen starvation phase.

From signal transduction to autophagy of plant cell organelles: lessons from yeast and mammals and plant-specific features

Autophagy is an evolutionarily conserved intracellular process for the vacuolar degradation of cytoplasmic constituents. The central structures of this pathway are newly formed double-membrane vesicles (autophagosomes) that deliver excess or damaged cell components into the vacuole or lysosome for proteolytic degradation and monomer recycling. Cellular remodeling by autophagy allows organisms to survive extensive phases of nutrient starvation and exposure to abiotic and biotic stress. Autophagy was initially studied by electron microscopy in diverse organisms, followed by molecular and genetic analyses first in yeast and subsequently in mammals and plants. Experimental data demonstrate that the basic principles, mechanisms, and components characterized in yeast are conserved in mammals and plants to a large extent. However, distinct autophagy pathways appear to differ between kingdoms. Even though direct information remains scarce particularly for plants, the picture is emerging that the signal transduction cascades triggering autophagy and the mechanisms of organelle turnover evolved further in higher eukaryotes for optimization of nutrient recycling. Here, we summarize new research data on nitrogen starvation-induced signal transduction and organelle autophagy and integrate this knowledge into plant physiology.

Phosphorylation of the protein kinase A catalytic subunit is induced by cyclic AMP deficiency and physiological stresses in the fission yeast, Schizosaccharomyces pombe

In the fission yeast, Schizosaccharomyces pombe, cyclic AMP (cAMP)-dependent protein kinase (PKA) is not essential for viability under normal culturing conditions, making this organism attractive for investigating mechanisms of PKA regulation. Here we show that S. pombe cells carrying a deletion in the adenylate cyclase gene, cyr1, express markedly higher levels of the PKA catalytic subunit, Pka1, than wild type cells. Significantly, in cyr1Δ cells, but not wild type cells, a substantial proportion of Pka1 protein is hyperphosphorylated. Pka1 hyperphosphorylation is strongly induced in cyr1Δ cells, and to varying degrees in wild type cells, by both glucose starvation and stationary phase stresses, which are associated with reduced cAMP-dependent PKA activity, and by KCl stress, the cellular adaptation to which is dependent on PKA activity. Interestingly, hyperphosphorylation of Pka1 was not detected in either cyr1 + or cyr1Δ S. pombe strains carrying a deletion in the PKA regulatory subunit gene, cgs1, under any of the tested conditions. Our results demonstrate the existence of a cAMP-independent mechanism of PKA catalytic subunit phosphorylation, which we propose could serve as a mechanism for inducing or maintaining specific PKA functions under conditions in which its cAMP-dependent activity is downregulated.

Biofilm Formation Capability of Enterococcus faecalis Cells in Starvation Phase and Its Susceptibility to Sodium Hypochlorite

IntroductionEnterococcus faecalis is commonly associated with persistent periapical infections. The physiologic state of the cells in the canal is probably closest to the starvation state. However, the biofilm formation capability of starved E. faecalis cells on human dentin and the susceptibility of the biofilm to 5.25% sodium hypochlorite remain poorly understood. MethodsE. faecalis American Type Culture Collection (ATCC) 29212 in different growth phases were incubated on human dentin and polystyrene blocks. Scanning electron microscopy and biofilm assay were used to investigate the biofilm formation capability of these cells. The susceptibility of the biofilm to 5.25% NaClO was also determined by the plate count method. ResultsScanning electron microscopy and biofilm assay showed that starved cells were able to form biofilm on dentin with reduced efficiency as compared with the cells in the exponential phase and stationary phase (p < 0.05). Biofilm grown on dentin harbored more cells than polystyrene (p < 0.05). Biofilms of starved cells were more resistant to 5.25% NaClO than those of stationary cells (p < 0.05), and the impact of 5.25%NaClO on them decreased as the biofilm matured. ConclusionE. faecalis cells in the starvation phase could develop biofilm on human dentin, which is responsive to 5.25% NaClO. It may contribute to the predominant role of E. faecalis involved in persistent periapical infections.

An experimental study on short-term changes in the anaerobic oxidation of methane in response to varying methane and sulfate fluxes

Abstract. A major role in regulation of global methane fluxes has been attributed to the process of anaerobic oxidation of methane (AOM), which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these energy limited, slow growing microorganisms with generation times of 3–7 months respond to rapid natural variations in methane fluxes at cold seeps. We used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their responses to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ~2 mM and 28 mM, respectively, we measured constant rates of AOM and sulfate reduction (SR) for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow velocities of 30 m yr−1, ca. 50% of the methane was consumed by the anaerobic methanotrophic (ANME) population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 50% was observed, and 45% of the methane was consumed. Hence, the marine anaerobic methanotrophs (ANME) are capable of oxidizing substantial amounts of methane over a wide and variable range of fluxes of the reaction educts.

Functional Significance and Morphological Characterization of Starvation-Induced Autophagy in the Adult Heart

To examine the functional significance and morphological characteristics of starvation-induced autophagy in the adult heart, we made green fluorescent protein-microtubule-associated protein 1-light chain 3 (LC3) transgenic mice starve for up to 3 days. Electron microscopy revealed round, homogenous, electron-dense lipid droplet-like vacuoles that initially appeared in cardiomyocytes as early as 12 hours after starvation; these vacuoles were identified as lysosomes based on cathepsin D-immunopositive reactivity and acid phosphatase activity. The increase in the number of lysosomes depended on the starvation interval; typical autophagolysosomes with intracellular organelles also appeared, and their numbers increased at the later phases of starvation. Myocardial expression of autophagy-related proteins, LC3-II, cathepsin D, and ubiquitin, increased, whereas both myocardial ATP content and starvation integral decreased. Treatment with bafilomycin A1, an autophagy inhibitor, did not affect cardiac function in normally fed mice but significantly depressed cardiac function and caused significant left ventricular dilatation in mice starved for 3 days. The cardiomyocytes were occupied with markedly accumulated lysosomes in starved mice treated with bafilomycin A1, and both the myocardial amino acid content, which was increased during starvation, and the myocardial ATP content were severely decreased, potentially contributing to cardiac dysfunction. The present findings suggest a critical role of autophagy in the maintenance of cardiac function during starvation in the adult.

A trade-off between growth and starvation endurance in a pit-building antlion

Trade-offs have a central role in evolutionary ecology and life-history theory. Here, we present evidence for the existence of a rarely studied trade-off between growth rate and starvation endurance in larvae of a pit-building antlion. We first manipulated antlions' feeding regime and obtained a spectrum of growth rates. Next, we starved the antlions and documented their rate of mass loss. Antlions growing faster during the feeding phase also lost mass faster during the successive starvation period, implying the existence of an induced trade-off between fast growth and starvation endurance. Finally, we fed all antlions with prey items of similar mass and measured both the giving-up prey mass (i.e. the remaining body mass of the prey that was not converted into predator body mass), and growth efficiency of antlions (i.e. proportion of prey consumed, negatively correlated with giving-up prey mass). The giving-up mass was negatively correlated with the growth rate of the antlions during the feeding phase, and positively correlated with their growth rate during the starvation phase (the opposite pattern was evident when examining growth efficiency), incongruently with the common phenomenon of growth compensation (i.e. extracting more of the prey after a starvation period). We suggest that antlion larvae can adopt a physiological mode bounded by two extremes: one extreme is adapted to starvation, involving reduced metabolic rates but also reduced capability to exploit prey, while the other is adapted to fast growth, allowing an efficient exploitation of prey, but at the expense of lowered starvation endurance.

Rethinking the Triad of Diabetes Management in the New Millennium

Historically, few individuals developed what is now known as type 2 diabetes, because a sedentary lifestyle and access to calories in excess of daily requirements was an unimaginable luxury for all but a few. When insulin-requiring diabetes did occur, it was extremely rare. For centuries, the only therapeutic options were dietary management and the promotion of physical activity. However, these strategies were usually short-lived. Author Michael Bliss, in his book, The Discovery of Insulin , describes in detail many of the early diets used to treat diabetes.1 One, known as the Allen Starvation Diet, was prescribed for the treatment of diabetes from 1910 to 1921.2 The goal of this diet was to extend life for several months to years. The nutritional strategies of this “starvation” approach are outlined in alarming detail in the 1921 4th edition of the book, The Allen (Starvation) Treatment of Diabetes with a Series of Graduated Diets. 2 The book, co-written by a dietitian, included the following starvation procedure: fasting the affected individual until glucosuria cleared, then initiating the consumption of moderate quantities of protein and fat with only small amounts of carbohydrate. The starvation diet also suggested the inclusion of 1.5 oz of whiskey. The alcohol provided additional calories as well as helped to make patients more comfortable as they were starving. The book then provided a series of maintenance diets that could be used after the starvation phase had reduced glucosuria. The book's …

Neuropsychologische Befunde bei Anorexia und Bulimia nervosa im Kindes- und Jugendalter

Anorexia nervosa and Bulimia nervosa are common chronic psychiatric diseases afflicting in particular female adolescents. During the acute phase of starvation a number of hormonal, neuropsychological and cerebral morphological changes occur. Some of these abnormalities are only partly reversible. Psychiatric comorbidities complicate the clinical picture and aggravate appropriate therapeutic interventions. The following review describes in detail the neuropsychological impairments in eating disorders, potential factors influencing cognitive performance, and resulting implications for clinical every day life.

Improved production of human type II procollagen in the yeast Pichia pastoris in shake flasks by a wireless-controlled fed-batch system

BackgroundHere we describe a new technical solution for optimization of Pichia pastoris shake flask cultures with the example of production of stable human type II collagen. Production of recombinant proteins in P. pastoris is usually performed by controlling gene expression with the strong AOX1 promoter, which is induced by addition of methanol. Optimization of processes using the AOX1 promoter in P. pastoris is generally done in bioreactors by fed-batch fermentation with a controlled continuous addition of methanol for avoiding methanol toxification and carbon/energy starvation. The development of feeding protocols and the study of AOX1-controlled recombinant protein production have been largely made in shake flasks, although shake flasks have very limited possibilities for measurement and control.ResultsBy applying on-line pO2 monitoring we demonstrate that the widely used pulse feeding of methanol results in long phases of methanol exhaustion and consequently low expression of AOX1 controlled genes. Furthermore, we provide a solution to apply the fed-batch strategy in shake flasks. The presented solution applies a wireless feeding unit which can be flexibly positioned and allows the use of computer-controlled feeding profiles.By using the human collagen II as an example we show that a quasi-continuous feeding profile, being the simplest way of a fed-batch fermentation, results in a higher production level of human collagen II. Moreover, the product has a higher proteolytic stability compared to control cultures due to the increased expression of human collagen prolyl 4-hydroxylase as monitored by mRNA and protein levels.ConclusionThe recommended standard protocol for methanol addition in shake flasks using pulse feeding is non-optimal and leads to repeated long phases of methanol starvation. The problem can be solved by applying the fed-batch technology. The presented wireless feeding unit, together with an on-line monitoring system offers a flexible, simple, and low-cost solution for initial optimization of the production in shake flasks which can be performed in parallel. By this way the fed-batch strategy can be applied from the early screening steps also in laboratories which do not have access to high-cost and complicated bioreactor systems.

Plant response to nitrate starvation is determined by N storage capacity matched by nitrate uptake capacity in two Arabidopsis genotypes

In a low-input agricultural context, plants facing temporal nutrient deficiencies need to be efficient. By comparing the effects of NO(3)(-)-starvation in two lines of Arabidopsis thaliana (RIL282 and 432 from the Bay-0xShahdara population), this study aimed to screen the physiological mechanisms allowing one genotype to withstand NO(3)(-)-deprivation better than another and to rate the relative importance of processes such as nitrate uptake, storage, and recycling. These two lines, chosen because of their contrasted shoot N contents for identical shoot biomass under N-replete conditions, underwent a 10 d nitrate starvation after 28 d of culture at 5 mM NO(3)(-). It was demonstrated that line 432 coped better with NO(3)(-)-starvation, producing higher shoot and root biomass and sustaining maximal growth for a longer time. However, both lines exhibited similar features under NO(3)(-)-starvation conditions. In particular, the nitrate pool underwent the same drastic and early depletion, whereas the protein pool was increased to a similar extent. Nitrate remobilization rate was identical too. It was proportional to nitrate content in both shoots and roots, but it was higher in roots. One difference emerged: line 432 had a higher nitrate content at the beginning of the starvation phase. This suggests that to overcome NO(3)(-)-starvation, line 432 did not directly rely on the N pool composition, nor on nitrate remobilization efficiency, but on higher nitrate storage capacities prior to NO(3)(-)-starvation. Moreover, the higher resistance of 432 corresponded to a higher nitrate uptake capacity and a 2-9-fold higher expression of AtNRT1.1, AtNRT2.1, and AtNRT2.4 genes, suggesting that the corresponding nitrate transporters may be preferentially involved under fluctuating N supply conditions.

Utilization of a chloroplast membrane sulfolipid as a major internal sulfur source for protein synthesis in the early phase of sulfur starvation in Chlamydomonas reinhardtii

Information is limited on sulfur (S)-sources inside plant cells for synthesis of the proteins for acclimation to S-starvation. We found that a green alga, Chlamydomonas reinhardtii, when transferred to S-starved conditions, degrades 85% of a chloroplast membrane lipid, sulfoquinovosyl diacylglycerol (SQDG), to redistribute its S to a large part of protein fraction as early as by 6 h. Furthermore, the degradation of SQDG preceded that of proteins such as ribulose bisphosphate carboxylase/oxygenase, the candidates of internal S-sources. SQDG was thus demonstrated to yield a major internal S-source for protein synthesis during the early phase of acclimation process to S-starvation.

Development and resistance of a biofilm in a planar fracture during biostimulation, starvation, and varying flow conditions

Investigations of biofilms in a planar fracture are required to develop a biobarrier concept in aquifers. A glass-fracture apparatus was designed to monitor a biofilm under three phases: biostimulation, starvation, and increased flow. Direct observations were performed using a light probe whereas indirect indications were obtained by enumerating planktonic bacteria, monitoring the oxidation–reduction potential (ORP), and interpreting tracer experiments using an analytical model for two-dimensional advection-dispersion. Biofilm clusters developed along the flow lines before extending to a fully-connected biofilm, covering 500 cm2 after 50 d. The starvation phase favoured bacterial attachment at first followed by detachment, which was accentuated by increases in groundwater velocity. The ORP declined over the three experimental phases and was significantly related to the distance from the biostimulation zone. The modeling suggested that an increase in transverse dispersion within the fracture only occurs during the biostimulation phase. Key words: fractured rock, groundwater flow, biofilms, biobarriers, advection–dispersion model, biostimulation, starvation, oxidation–reduction potential.

Red knots give up flight capacity and defend food processing capacity during winter starvation

Summary 1During the last phase of starvation, animals depend mainly on protein breakdown. All organs are a potential protein source. Do starving animals prevent particular organs from being catabolized in order to defend certain functions? In this study we investigated if starving birds maintain locomotion and digestion capacities, both essential for the recovery process. 2We compared body composition data of healthy wintering and winter-starved red knots (Calidris canutus islandica), a long-distance migrating shorebird that breeds on High Arctic tundra in Canada and Greenland, and winters in temperate coastal areas such as the Wadden Sea and the British estuaries. Throughout the wintering period they eat hard-shelled molluscs ingested whole. 3Our results showed that winter-starved knots had catabolized 60·5% of their pectoral muscles. This was much more than the decrease in overall body mass (32·5%). As a result, their flight capacities will have been reduced. 4Winter-starved knots defended the muscular gizzard, which lost only 21·2% of its mass. As knots crack the ingested shellfish with their gizzard, the organ is essential for food processing. The intestines and liver were not defended; their atrophy equalled that of the pectoral muscles (60·6% and 61·3%, respectively). 5Comparison with data from the literature led to the conclusion that starving birds only defend organs that are essential to either obtain or process food. These organs are maintained at the minimal level of normal capacity. Other organs decrease below this level and may lose much of their functional capacity. 6Even in near-death situations, with low fitness prospects, organisms show interpretably adaptive changes in organ size.

Starvation is not a prerequisite for the formation of aerobic granules

Activated sludge with sludge volume index (SVI)(30) of 77 ml g(-1) and SVI(30) of 433 ml g(-1) was inoculated to start up reactors R1 and R2, respectively. In both R1 and R2, cycle time of 1 h and the influent chemical oxygen demand (COD) concentrations of 1,000 mg l(-1) were employed. Initial settling time of 2 min resulted in the loss of a substantial amount of biomass as wash-out and high effluent COD concentrations within the first week of operation. This implied that there was no starvation phase in each cycle of R1 and R2 during the first week of operation. However, aerobic granules with a size above 400 mum formed by day 7. Thus, it was concluded that starvation was not a prerequisite for the formation of aerobic granules. When cycle time was 1 h, the instability of aerobic granules was observed. When cycle time was prolonged to 1.5 h and granular sludge of 200 ml was used to start up reactor R3, the reactor R3 reached steady state within 1 week. SVI, size, and the morphology of granular sludge in R3 remained stable during the 47-day operation, which indicated that prolonged starvation time had positive effects on the stability of aerobic granules.

Tectonic evolution and paleogeography of the Mesozoic Pucará Basin, central Peru

The Pucará Basin of Peru is an elongate trough that subsided landward of a NNW-trending structural high during the Late Triassic–Early Jurassic. It formed as a postrift regional sag as the earlier Triassic fault-controlled Mitu rifts yoked together. The rift and transitional postrift basins were associated with a NW-striking sinistral shear zone that controlled isopachs and facies distributions and resulted in magmatism and mineralization along its trend. A distinct association of later dolomitization and MVT lead–zinc mineralization also occurs with these basin-forming shear zones. Although basaltic and andesitic extrusives are common, there is no evidence that the Pacific margin was a magmatic arc until the upper Pucará, and then only weakly developed in northern Peru. Except in the upper Pucará of northwest Peru, geochemical studies, including whole rock and trace element analyses, indicate that intercalations of volcanic material have intraplate rift affinities. The basin fill has a three-part stratigraphic subdivision, comprising lower and upper carbonate platforms with an intermediate phase of basin overdeepening and sediment starvation that resulted in a regional, organic-rich argillaceous drape. Stratigraphic accumulation was dominated by axial patterns of onlap and progradation, though facies characteristics show it was augmented by periodic flooding of the western basin margin high. Marine invertebrate fossils indicate normal marine salinities. The sedimentological interpretation is based on a SW–NE transect in the southern part of the Pucará Basin. The Chambará (Norian–Rhaetian) and Condorsinga (Toarcian) formations were constructed principally by shallow-water carbonate sedimentation in lagoon-like subtidal, intertidal, and supratidal paleoenvironments. The subtidal carbonate platform is dominated by oolitic grainstones with subordinate bioclastic packstones. Subordinate open-basin facies in the Chambará Formation consist principally of crinoidal packstones and bioclastic wackestones. In the intertidal and supratidal facies, evaporite pseudomorphs are common and generally associated with algal mats and widespread early diagenetic dolomitization. During the Chambará and Condorsinga, subsidence typically was balanced by carbonate production and shallow-water environments prevailed; the basin had the characteristics of an overfilled basin. Conversely, the intermediate late Rhaetian–Sinemurian stage of basin subsidence was marked by underfilled deep water conditions. This widespread transgressive inundation of the Pucará Basin, recorded in the argillaceous Aramachay stratigraphy, correlates with similar events in other Andean basins.