Nitrification and denitrification in a system of reciprocating jet bioreactor

Concept of separation of stages coupled with novel design of reciprocating jet bioreactor have been incorporated in this research for the development of high efficiency treatment system for contaminated wastewaters.Evaluation of pilot plant data reveals that a three stage reciprocating jet bioreactor system could be effectively employed for nitrification and denitrification of highly polluted wastewater obtained from Berlin wastewater treatment plant. Such a system with COD destruction stage (residence time 1–3 hours) followed by nitrification stage (residence time 3–4.5 hours) and denitrification stage (residence time 0.3 hours) gives COD destruction rate upto 58 kg COD/(m³ day), nitrification rate upto 3.2 NH ₄ ⁺ -N/(m³ day) and denitrification rate upto 28 kg NO ₃ ^– -N/(m³ day) while providing COD, NH ₄ ⁺ -N and NO ₃ ^– -N conversion of more than 90%.Nitrification and denitrification of wastewater at such a short residence time is possible mainly due to the employment of reciprocating jet bioreactor system.Paper presented at the Third Joint Schlesinger Seminar on Transport phenomena and processes in biological systems, Technion — Israel Institute of Technology, Haifa, Israel, May 8–9, 1990     

Stoichiometric design of metabolic networks: multifunctionality,clusters, optimization,weak and strong robustness

Starting from a limited set of reactions describing changes in the carbon skeleton of biochemical compounds complete sets of metabolic networks are constructed. The networks are characterized by the number and types of participating reactions. Elementary networks are defined by the condition that a specific chemical conversion can be performed by a set of given reactions and that this ability will be lost by elimination of any of these reactions. Groups of networks are identified with respect to their ability to perform a certain number of metabolic conversions in an elementary way which are called the network’s functions. The number of the network functions defines the degree of multifunctionality. Transitions between networks and mutations of networks are defined by exchanges of single reactions. Different mutations exist such as gain or loss of function mutations and neutral mutations. Based on these mutations neighbourhood relations between networks are established which are described in a graph theoretical way. Basic properties of these graphs are determined such as diameter, connectedness, distance distribution of pairs of vertices. A concept is developed to quantify the robustness of networks against changes in their stoichiometry where we distinguish between strong and weak robustness. Evolutionary algorithms are applied to study the development of network populations under constant and time dependent environmental conditions. It is shown that the populations evolve toward clusters of networks performing a common function and which are closely neighboured. Under changing environmental conditions multifunctional networks prove to be optimal and will be selected.     

Effect of Light Intensity on Circadian Activity in Developing Japanese Quail

The effects of constant light on the expression of the circadian rhythm of feeding activity in Japanese quail, and in particular on the clarity of the rhythm were investigated. We used 46 4-week-old birds (35 females and 11 males) issued from two lines selected for a more (line R: 25 females and 10 males) or less (line A: 10 females and 1 male) clear circadian rhythm of feeding activity. The birds, were placed successively under three light schedules: constant darkness (DD), constant dim green light (LLdim) and constant bright light (LLbright). Schedules were changed every 2 weeks. Feeding activity was recorded continuously, analysed by autocorrelation and spectral analysis, and the ratio of the correlation coefficients and the area of the spectrum peak were used as indexes to quantify the clarity of the circadian rhythm. During the experiment, some birds showed gonadal development. Therefore, we analysed separately birds showing either a high or low degree of sexual development at the end of the experiment. In DD, 35 birds showed a circadian feeding rhythm with a mean period of 22.5 ± 0.1 h, whereas 11 birds showed an arrhythmic activity. In LLdim, 27 birds were rhythmic (22 birds R and 5 birds A), and in LLbright, only 3 birds showed a rhythmic circadian activity. For the R-line birds (for females and males), the rhythm clarity decreased in LLdim compared to DD, except for the not developed females. For the A-line birds (for females), the rhythm clarity of the immature birds increased in LLdim and that of the developed birds remained stable. In LLbright, circadian activity became arrhythmic. In LLdim, the active phases of 12 birds showed two main peaks, with mean periods of 22.7 h and 25.1 h, respectively. Therefore, constant light appeared to have an inhibitory effect on the expression of the circadian rhythm. We postulate that two hierarchically coupled oscillators could control circadian feeding activity, and arrhythmia in LLbright could be the results of internal desynchronization of the pacemakers.     

Construction of recombination-deficient strains of Pseudomonas aeruginosa

Summary The rec-102 mutation had pleiotropic effects in Pseudomonas aeruginosa: low recombination proficiency in conjugation and transduction; high UV sensitivity; inability to induce pyocin R2 by mitomycin C; and increased susceptibility to mitomycin C and nalidixic acid. The rec-102 locus was mapped by R68.45-mediated conjugation in the 45 min region of the PAO chromosome, between argF and thr-9001. By selection for a marker in this region, rec-102 can be introduced into a P. aeruginosa strain of interest using an R68.45 rec-102 donor. The recombination-deficient strains constructed in this way were phenotypically similar to Escherichia coli recA mutants.     

Tropical rainforest flies carrying pathogens form stable associations with social nonhuman primates

Living in groups provides benefits but also incurs costs such as attracting disease vectors. For example, synanthropic flies associate with human settlements, and higher fly densities increase pathogen transmission. We investigated whether such associations also exist in highly mobile nonhuman primate (NHP) Groups. We studied flies in a group of wild sooty mangabeys (Cercocebus atys atys) and three communities of wild chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire. We observed markedly higher fly densities within both mangabey and chimpanzee groups. Using a mark–recapture experiment, we showed that flies stayed with the sooty mangabey group for up to 12 days and for up to 1.3 km. We also tested mangabey‐associated flies for pathogens infecting mangabeys in this ecosystem, Bacillus cereus biovar anthracis (Bcbva), causing sylvatic anthrax, and Treponema pallidum pertenue, causing yaws. Flies contained treponemal (6/103) and Bcbva (7/103) DNA. We cultured Bcbva from all PCR‐positive flies, confirming bacterial viability and suggesting that this bacterium might be transmitted and disseminated by flies. Whole genome sequences of Bcbva isolates revealed a diversity of Bcbva, probably derived from several sources. We conclude that flies actively track mangabeys and carry infectious bacterial pathogens; these associations represent an understudied cost of sociality and potentially expose many social animals to a diversity of pathogens.     

Effect of “osmotic stress” on protein and nucleic acid synthesis in isolated tobacco protoplasts

The incorporation of labeled precursors into RNAs and proteins of isolated tobacco (Nicotiana tabacum L.) leaf protoplasts decreases with increasing osmotic pressure in the incubation medium. The incorporation of precursors into RNA and proteins is linear for 15–18 h after the isolation of the protoplasts, irrespective of the osmolarity of the culture media. The uptake of precursors is also affected by the osmolarity of the medium. However, the osmotic stress-induced inhibition of incorporation of precursors into RNA and proteins is also apparent if the differences in uptake are taken into consideration in the calculation. Incorporation of ³²P into TMV-RNA is also inhibited by osmotic stress. As assayed by the double labeling ratio technique, osmotic stress has less unequivocal effect on TMV protein synthesis.Abbreviations PP protoplast - RNase ribonuclease - rRNA ribosomal ribonucleic acid - SDS sodium dodecyl sulfate - SSC 0.1 M Na-acetate in 0.15 M NaCl - TCA trichloroacetic acid - TMV tobacco mosaic virus     

The new TNM classification of malignant melanoma

The identification of increasingly powerful prognostic factors has led to sequential modifications of the cutaneous melanoma staging system. The American Joint Committee on Cancer (AJCC) recently proposed major revision of tumor node metastasis (TNM) categories and stage groupings for melanoma. The authors summarize the main characteristics of this new TNM classification of malignant melanoma. The importance of the novel technique - sentinel node biopsy - in the management of malignant melanoma is discussed.     

Major histocompatibility complex (MHC)-encoded HAM2 is necessary for antigenic peptide loading onto class I MHC molecules.

The mutant murine lymphoma cell line RMA-S is unable to present endogenous antigens due to its inability to efficiently assemble class I major histocompatibility complex molecules and antigenic peptides. Therefore, it has been suggested that RMA-S cells are defective either in peptide generation or in peptide transport into the endoplasmic reticulum, where class I major histocompatibility complex molecule assembly is believed to occur. As proteasomes and the putative peptide transporters HAM1 and HAM2 have been implicated in class I antigen processing, we have investigated their expression in RMA-S and its wild-type counterpart RMA. Both proteasomes and HAM1 proteins are expressed at similar levels and show identical subcellular distributions in the two cell lines. However, only one copy of the HAM2 gene is present in RMA-S cells, and it contains a point mutation that leads to a premature stop codon. Thus, the HAM2 protein is absent from RMA-S cells. These data demonstrate that HAM2 is essential for peptide loading onto class I molecules.     

Effects of decreased atmospheric deposition on the sulfur budgets of two Dutch moorland pools

The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982 to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO₄ ²⁻ concentrations after a decrease of atmospheric input. However, SO₄ ²⁻ concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused the unexpectedly high SO₄ ²⁻ concentrations. The possible supply of SO₄ ²⁻ from the sediment through regulation by (K-)Al-SO₄ containing minerals or desorption of SO₄ ²⁻ from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite, basaluminite and jurbanite indicated that SO₄ ²⁻ concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO₄ ²⁻ from peaty sediments may account for the estimated SO₄ ²⁻ supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation of reduced S, the amount of SO₄ ²⁻ may be provided which complements the decreasing depositional SO₄ ²⁻ input. In future research these two mechanisms need to be investigated.