The Microbial Associations Developing on Experimental Trickling Filters Irrigated with Domestic Sewage

S ummary . The bacterial flora of the film which developed on experimental trickling filters irrigated with domestic sewage was dominated by Acinetobacter and yellow-pigmented Gram negative rod-shaped organisms and it was deduced that purification in certain aerobic waste treatment processes may depend upon an association of these 2 organisms. Further evaluation of the operational procedures likely to have a selective influence on the microbial association which becomes dominant was made in studies using synthetic sewage.     

Patterns of accumulation resulting from Taxes and changes in motility of micro-organisms

Summary An analysis is made of the development of patterns of accumulation of micro-organisms, as governed by tactic responses, changes in motility, and the effects of diffusion.When a soluble crystal is placed in a suspension of micro-organisms, the first manifestation is the development of a clear zone surrounding the crystal. This effect is a physical one, produced by a transfer of momentum from the solute molecules to the organisms.As the solute spreads and its boundary moves more slowly, the organisms are distributed in patterns which depend upon the occurrence of tactic responses and the influence of the solute upon motility. A congregation in the zone occupied by the solute can correspond either to a positive chemotaxis or to an inhibition of motility by the solute. Conversely, a withdrawal from the solute can signal either a negative chemotaxis or an enhancement of motility by the solute.The proper interpretation of the patterns described in Figs. 10 and 11 requires a microscopic study of individual organisms, in which the effect of the reagent upon motility is noted.     

The energetic consequences of hydrogen gradients in methanogenic ecosystems

Abstract In the dense microbial aggregates usually found in methanogenic waste water treatment systems, hydrogen has to diffuse from producers to consumers at considerable rates. The ensuing hydrogen gradients dissipate part of the potential energy that would otherwise be available to the hydrogen-consuming organisms. The present paper evaluates the energetic consequences of this phenomenon.     

Mechanisms of animal navigation in odor plumes

Chemical signals mediate many of life's processes. For organisms that use these signals to orient and navigate in their environment, where and when these cues are encountered is crucial in determining behavioral responses. In air and water, fluid mechanics impinge directly upon the distribution of odorous molecules in time and space. Animals frequently employ behavioral mechanisms that allow them to take advantage of both chemical and fluid dynamic information in order to move toward the source. In turbulent plumes, where odor is patchily distributed, animals are exposed to a highly intermittent signal. The most detailed studies that have attempted to measure fluid dynamic conditions, odor plume structure, and resultant orientation behavior have involved moths, crabs, and lobsters. The behavioral mechanisms employed by these organisms are different but generally integrate some form of chemically modulated orientation (chemotaxis) with a visual or mechanical assessment of flow conditions in order to steer up-current or upwind (rheo- or anemo-taxis, respectively). Across-stream turns are another conspicuous feature of odor-modulated tracks of a variety of organisms in different fluid conditions. In some cases, turning is initiated by detection of the lateral edges of a well-defined plume (crabs), whereas in other animals turning appears to be steered according to an internally generated program modulated by odor contacts (moth counterturning). Other organisms such as birds and fish may use similar mechanisms, but the experimental data for these organisms is not yet as convincing. The behavioral strategies employed by a variety of animals result in orientation responses that are appropriate for the dispersed, intermittent plumes dictated by the fluid-mechanical conditions in the environments that these different macroscopic organisms inhabit.     

Immunosuppression by avirulent,pseudohyphal forms ofCryptococcus neoformans

Our previous reports have shown that animals inoculated for 8 weeks with 1 × 10⁵ pseudohyphal, avirulentC. neoformans exhibited prolonged survival upon challenge with virulent cryptococci. This paper described a transient phase of immunosuppression which occurs during the initial weeks of the immunization protocol. Animals injected with pseudohyphal organisms had depressed responses to T and B-cell mitogens. In addition, they had lowered responses to immunization with sheep erythrocytes. Both humoral and cell mediated responses were affected.     

Immunosuppression by avirulent,pseudohyphal forms ofCryptococcus neoformans

Our previous reports have shown that animals inoculated for 8 weeks with 1×10₅ pseudohyphal, avirulentC. neoformans exhibited prolonged survival upon challenge with virulent cryptococci. This paper described a transient phase of immunosuppression which occurs during the initial weeks of the immunization protocol. Animals injected with pseudohyphal organisms had depressed responses to T and B-cell mitogens. In addition, they had lowered responses to immunization with sheep erythrocytes. Both humoral and cell mediated responses were affected.     

Photoreceptors for biosynthesis, energy storage and vision

Abstract Living organisms use light as a source of energy and as a means of obtaining information about their environment. Photoreactivating enzyme, provitamins D, retinal (rhodopsins and bacteriorhodopsin), porphyrins (chlorophyll, protochlorophyll and heme), photosynthetic accessory pigments (carotenoids and bilins), phytochrome and riboflavin: these are the molecules which life has settled upon to play the role of light receptor. For some of these photoreceptor molecules a great deal is now known about the chemistry which they perform upon absorbing light; for others virtually nothing is known. Riboflavin, the molecule believed to be functioning in a variety of organisms as the receptor for physiological responses to blue light, is an especially interesting case. Its widespread occurrence in cellular roles other than photoreception make it difficult to separate out the particular flavin which functions as the photoreceptor. It represents a case of a photoreceptor which is at once ubiquitous and elusive.     

The differential response of human dendritic cells to live and killed Neisseria meningitidis

There is currently no effective vaccine for Neisseria meningitidis (Nm) serogroup B. Generation of optimal immune responses to meningococci could be achieved by targeting meningococcal antigens to human dendritic cells (DCs). Recent studies have shown that diverse DC responses and subsequent generation of protective immunity can be observed if the microbes are viable or killed. This is important because the host is likely to be exposed to both live and killed bacteria during natural infection. There are currently few data on comparative DC responses to live and killed meningococci. We show here that exposure of human DC to live meningococci does not result in a typical maturation response, as determined by the failure to upregulate CD40, CD86, HLA-DR and HLA-Class I. Despite this, live meningococci were potent inducers of IL-12 and IL-10, although the ratios of these cytokines differed from those to killed organisms. Our data also suggest that enhanced phagocytosis of killed organisms compared with live may be responsible for the differential cytokine responses, involving an autocrine IL-10-dependent mechanism. The consequences of these findings upon the effectiveness of antigen presentation and T-cell responses are currently under investigation.     

Thermal composting of faecal matter as treatment and possible disinfection method--laboratory-scale and pilot-scale studies

When using toilets where the urine and faeces are collected separately for reuse as nutrients in agriculture, the collected matter should be disinfected. One way to do this is by thermal composting. Composting of different material mixes was investigated in a laboratory-scale experiment. This showed that the best mixture for dry thermal composting was a mix of faeces, food waste and amendment. The urine was collected separately by use of urine-diverting toilets. A new method was developed to mathematically evaluate and estimate the safety margins of pathogen inactivation during thermal composting. The method is based upon a mathematical calculation of the number of times total inactivation (at least 12log(10) reduction) of the organisms is achieved. In a pilot-scale experiment, the disinfection of a faeces/food waste mix was performed with a calculated safety margin of more than 37 times the total die-off of Enteroviruses and some 550 times that of Ascaris. Thus, well functioning composting seems to be effective for disinfection of faecal matter. To get a high temperature in all of the material, the reactor has to have sufficient insulation. A major disadvantage is the initial need for handling the raw un-disinfected material. The degradation of the organic matter in the compost was almost 75%, resulting in a small final volume that could safely be recycled.     

Induction of primary and inhibition of secondary antibody response to hapten by hapten conjugates of type III pneumococcal polysaccharide.

Tri- or dinitrophenylated pneumococcal polysaccharide type III (TNP- or DNP SIII)) induced a primary 19S anti-TNP response without generating immunological memory to the hapten in LAF₁ mice. Hapten-hemocyanin (TNP-KLH) or hapten conjugates of B. abortus organisms (DNP-BA) induced both 19S and 7S primary responses and memory to the hapten. Spleen cells from mice immunized with TNP-KLH or DNP-BA did not give adoptive memory responses upon challenge with hapten-SIII and, in fact, were inhibited from responding to their homologous hapten conjugates by simultaneous injection of hapten-SIII. Incubation of TNP-KLH-primed spleen cells for as short as 5 min at 0 °C with 10 μg of TNP-SIII per milliliter virtually abolished their ability to give 19S and 7S memory responses to TNP-KLH upon transfer into irradiated recipients. It is suggested that a difference in avidity and/or number of anti-TNP receptors per cell between virgin and primed B cells may be an important factor in determining whether the cells will be stimulated or inhibited by exposure to hapten-SIII. Another factor may be a difference between virgin and memory cells in their requirement for T-cell help.     

Characteristics of aerobic,solid substrate fermentation of swine waste-corn mixtures

Summary Aerobic fermentation of swine waste combined with corn produced differences in microbial and biochemical patterns dependent on use of fresh or stored excrement. Lactic acid fermentation and odor control resulted with either waste. Homofermentative lactic acid bacteria were present initially at 10⁷ organisms/dry g with stored waste-corn cultures and total microflora amounted to 10⁸ organisms/dry g. Fresh waste-corn fermentations initially yielded heterofermentative lactic acid bacteria at 10⁷ organisms/dry g and total viable population was 10⁹ organisms/dry g. These respective groups of lactic acid bacteria dominated from 12 through 144 h in cultures with either waste, and acid production (0.2 meq/dry g) decreased pH by 2 units to 4.5. The major acid component with stored waste-corn was lactic acid, whereas fresh waste-corn fermentation produced both lactic and homologous fatty acids from acetic through valeric acid. Coliform bacteria present initially at 10⁵ organisms/dry g in stored waste-corn cultures were not detected after 36 h; coliform bacteria in fresh waste-corn fermentations persisted at 10⁶ organisms/dry g. A silage-like fermentation product resulted which may have use in animal feed formulations.     

Microbial population of feedlot waste and associated sites

A quantitative determination was made every 2 months for a year of the microflora of beef cattle waste and runoff at a medium-sized midwestern feedlot. Counts were obtained for selected groups of organisms in waste taken from paved areas of pens cleaned daily and, therefore, reflect the flora of raw waste. Overall, in terms of viable count per gram dry weight, the feedlot waste contained 10¹⁰ total organisms, 10⁹ anaerobes, 10⁸ gram-negative bacteria, 10⁷ coliforms, 10⁶ sporeformers, and 10⁵ yeasts, fungi, and streptomycetes. The specific numbers and pattern of these groups of organisms varied only slightly during the study in spite of a wide variation in weather. Data indicate that little microbial growth occurs in the waste as it exists in the feedlot. Runoff from the pens contained the same general population pattern but with greater variation attributable to volume of liquid. Comparable determinations of an associated field disposal area (before and after cropping), stockpiled waste, and elevated dirt areas in the pens indicate that fungi, and especially streptomycetes, are the aerobic organisms most associated with final stabilization of the waste. Yeasts, which are the dominant type of organism in the ensiled corn fed the cattle, do not occur in large numbers in the animal waste. Large ditches receiving runoff and subsurface water from the fields have a population similar to the runoff but with fewer coliforms.     

塑料添加剂向生态环境中的释放与迁移研究进展

塑料废弃物,尤其是粒径小于5 mm的微塑料造成的环境污染问题已引起全球的普遍关注。塑料制品在生产过程中常使用多种添加剂,以提高聚合物的性能并延长其使用寿命。然而,在废弃塑料制品的回收及自然老化过程中,这些添加剂会不断释放出来,对生态环境的安全与人类的健康产生威胁。综述了近年来国内外塑料添加剂的使用情况及其向生态环境释放与迁移等方面的研究进展,具体包括常用塑料添加剂的种类、废弃物塑料回收和塑料老化过程中添加剂向生态环境中的释放与迁移及机制等。未来需要更加关注绿色塑料添加剂的研发、废弃塑料回收工艺的改进以及关于塑料添加剂的释放、在各类环境介质中的迁移转化以及在生态系统各个圈层间的相互作用方面的系统性的研究,并构建相应的迁移模型评估塑料添加剂产生的生态风险。     

Fermentation of Feedlot Waste Filtrate by Fungi and Streptomycetes

The soluble and dispersed nitrogen and carbon components in the filtrate fraction of cattle feedlot waste are a potential nutrient source from which single-cell protein could be produced for animal feeds. The ability of more than 200 fungi and streptomycetes to grow in this liquid was determined; these included isolates from the waste and associated sources, as well as organisms maintained in the Culture Collection of the Agricultural Research Service in Peoria, Ill. Utilization of waste nutrients was measured by changes in nitrogen content and chemical oxygen demand. Only 20% of the organisms were able to grow appreciably in the filtrate. Of these, dry-weight yields varied from 0.6 to 2.7 g of mycelium per liter; from 21 to 50% of the nitrogen in the filtrates was used during growth, whereas chemical oxygen demand levels diminished from 4 to 60%. In general, streptomycetes isolated from the feedlot used nutrients from the filtrates better than fungi did. Addition of readily available carbon sources such as glucose or whey significantly increased (as much as sixfold) cell yields of selected organisms and promoted better utilization of nitrogen (from two- to threefold); the effect on chemical oxygen demand varied (0 to 33% increase).     

Assessing immune competence in pigs by immunization with tetanus toxoid

Immune competence can be tested by challenging organisms with a set of infectious agents. However, disease control requirements impose restrictions on the infliction of infections upon domestic pigs. Alternatively, vaccinations induce detectable immune responses that reflect immune competence. Here, we tested this approach with tetanus toxoid (TT) in young domestic pigs. To optimize the vaccination protocol, we immunized the pigs with a commercial TT vaccine at the age of 21 or 35 days. Booster immunizations were performed either 14 or 21 days later. TT-specific antibodies in plasma as well as lymphoproliferative responses were determined both 7 and 14 days after booster immunization using ELISA and lymphocyte transformation tests, respectively. In addition, general IgG and IgM plasma concentrations and mitogen-induced proliferation were measured. The highest TT-specific antibody responses were detected when blood samples were collected 1 week after a booster immunization conducted 21 days after primary immunization. The pigs’ age at primary immunization did not have a significant influence on TT-specific antibody responses. Similarly, the TT-specific proliferative responses were highest when blood samples were collected 1 week after booster immunization, while age and time of primary and booster immunization were irrelevant in our setup. While general IgG and IgM plasma levels were highly age dependent, there were no significant age effects for TT-specific immune responses. In addition, mitogen-induced proliferation was independent of immunization as well as blood sampling protocols. In summary, our model of TT vaccination provides an interesting approach for the assessment of immune competence in young pigs. The detected vaccination effects were not biased by age, even though our data were acquired from immune systems that were under development during our tests.     

Biotin Production and Utilization in a Sewage Treatment Lagoon

Biotin, in a sewage oxidation lagoon also receiving potato processing wastes, was observed to increase two logs during the summer period of waste stabilization and then to decline to near earlier concentrations. Three organisms, Aerobacter aerogenes, Chlorella vulgaris, and Thiocapsa floridana, were at least partially responsible for these fluctuations; the latter two organisms were associated with biotin utilization and the former with biotin production. Since copious quantities of biotin are produced in these waste treatment facilities, the vitamin may act as a useful indicator of microbial action on certain organic molecules, especially in domestic and industrial wastes such as those from municipalities and potato and sugar beet processing plants. Furthermore, the presence of biotin in rivers and streams may be indicative of the discharge of incompletely stabilized wastes from these sources.     

A review of the sustainable value of effluents and sludges from wastewater stabilization ponds

Sludges and liquids from wastewater stabilization ponds are cost effective by-products useful for agriculture, aquaculture and for manufacturing building materials. They represent valuable sustainable resources as raw materials to support fisheries for human consumption, to produce animal feed derived from single cell algal proteins and aquatic weeds. Biogas from waste fermentation represents a significant tertiary product.Stabilization ponds are dynamic, low-cost waste recycling ecosystems comprising complex communities of algae, virus, protozoa, rotifers, insects, crustaceans and fungi. These organisms interact and modify the organic content of the waste to produce effluents which need little further investment in treatment.The economic, societal and sustainable value of stabilization ponds is governed by the management regime and the use for which the sludge and effluent is intended. Fish, ducks, prawn and algal protein production rely upon adequately treated effluent. This is particularly valuable for irrigation in arid and semi-arid climates, where natural waters are insufficient and nutrient depleted. Oxidation ponds provide sustainable mechanisms for dealing with sewage and for reducing the risk of infection from parasites and the effects of toxins. The resulting sludges can be used as fertilizer or be composted with local vegetation. Aerobic and anaerobic digestion, lime treatment and pasteurisation are used to improve sludge acceptability and utility to enhance its value as a sustainable resource.     

Chlamydomonas reinhardtii mutants abnormal in their responses to phosphorus deprivation.

P-starved plants scavenge inorganic phosphate (Pi) by developing elevated rates of Pi uptake, synthesizing extracellular phosphatases, and secreting organic acids. To elucidate mechanisms controlling these acclimation responses in photosynthetic organisms, we characterized the responses of the green alga Chlamydomonas reinhardtii to P starvation and developed screens for isolating mutants (designated psr [phosphorus-stress response]) abnormal in their responses to environmental levels of Pi. The psr1-1 mutant was identified in a selection for cells that survived exposure to high concentrations of radioactive Pi. psr1-2 and psr2 were isolated as strains with aberrant levels of extracellular phosphatase activity during P-deficient or nutrient-replete growth. The psr1-1 and psr1-2 mutants were phenotypically similar, and the lesions in these strains were recessive and allelic. They exhibited no increase in extracellular phosphatase activity or Pi uptake upon starvation. Furthermore, when placed in medium devoid of P, the psr1 strains lost photosynthetic O2 evolution and stopped growing more rapidly than wild-type cells; they may not be as efficient as wild-type cells at scavenging/accessing P stores. In contrast, psr2 showed elevated extracellular phosphatase activity during growth in nutrient-replete medium, and the mutation was dominant. The mutant phenotypes and the roles of Psr1 and Psr2 in P-limitation responses are discussed.     

Chk1 in the DNA damage response: conserved roles from yeasts to mammals

Chk1 is an evolutionarily conserved protein kinase that functions to ensure genomic integrity upon genotoxic stress. Studies to date have revealed striking similarities among Chk1 pathways of different organisms. In this review we discuss what is known about Chk1 activation and what downstream factors are regulated by Chk1 to counter replication blocks and DNA damage induced by UV, IR, and other genotoxic agents. Where applicable, we also compare the role of Chk1 with that of the Chk2 protein kinase in the checkpoint responses.