A Dynamic Model of the Environmental Kuznets Curve : Turning Point and Public Poliy

We set up a simple dynamic macroeconomic model with (i) polluting consump- tion and a preference for a clean environment, (ii) increasing returns in abate- ment giving rise to an EKC and (iii) sustained growth resulting from a linear final-output technology. The model captures two sorts of market failures caused by external effects associated with consumption and environmental effort. This model is employed to investigate the determinants of the turning point and the (relative) effectiveness of different public policy measures aimed at a reduction of the environmental burden. Moreover, the model offers a potential explana- tion of an N-shaped pollution-income relation. Finally, it is shown that the model is compatible with most empirical regularities on economic growth and the environment.Environmental Kuznets Curve, Pollution, Abatement, External Ef- fects, Economic Growth, Public Policy

The Concept of Multiple-Nutrient-Limited Growth of Microorganisms and Some of Its Possible Applications in Biotechnology Processes

Justus von Liebig's 'Law of the minimum' states that usually one nutrient restricts the maximum quantity of biomass that can be produced within a system where all other nutrients are available in excess. This general rule has been applied also to the growth of microorganisms, e.g., by adjusting the relative concentrations of the individual nutrients in growth media such that one of them, in the case of heterotrophic microbes usually the carbon source, determines the maximum cell density that can be obtained in a culture. However, recent experimental data from chemostats have demonstrated that growth of microbial cultures can be limited simultaneously by two or more nutrients. The experimental evidence supporting the limitation of growth by multiple nutrients is reviewed here, and a concept is presented that allows predicting the zones where multiple-nutrient-limited growth occurs. The information so far available indicates that multiple-nutrient-limited growth conditions allow to force cells into a physiological status that cannot be achieved under traditional single-nutrient-limited growth conditions. Two examples are given which demonstrate that cultivation of microbial cells under multiple-nutrient-limited growth conditions can be used to enhance the productivity of biotechnological processes

A Dynamic Model of the Environmental Kuznets Curve: Turning Point and Public Policy

We set up a simple dynamic macroeconomic model with (i) polluting consumption and a preference for a clean environment, (ii) increasing returns in abatement giving rise to an EKC and (iii) sustained growth resulting from a linear final-output technology. There are two sorts of market failures caused by external effects associated with consumption and environmental effort. The model is employed to investigate the determinants of the turning point and the cost effectiveness of different public policies aimed at a reduction of the environmental burden. Moreover, the model offers a potential explanation of an N-shaped pollution-income relation. It is shown that the model is compatible with most empirical regularities on economic growth and the environmen

Cytometric methods for measuring bacteria in water: advantages, pitfalls and applications

Rapid detection of microbial cells is a challenge in microbiology, particularly when complex indigenous communities or subpopulations varying in viability, activity and physiological state are investigated. Flow cytometry (FCM) has developed during the last 30years into a multidisciplinary technique for analysing bacteria. When used correctly, FCM can provide a broad range of information at the single-cell level, including (but not limited to) total counts, size measurements, nucleic acid content, cell viability and activity, and detection of specific bacterial groups or species. The main advantage of FCM is that it is fast and easy to perform. It is a robust technique, which is adaptable to different types of samples and methods, and has much potential for automation. Hence, numerous FCM applications have emerged in industrial biotechnology, food and pharmaceutical quality control, routine monitoring of drinking water and wastewater systems, and microbial ecological research in soils and natural aquatic habitats. This review focuses on the information that can be gained from the analysis of bacteria in water, highlighting some of the main advantages, pitfalls and application

Transient repression of the synthesis of OmpF and aspartate transcarbamoylase in Escherichia K12 as a response to pollutant stress

The synthesis of total cellular proteins in Escherichia coli K12 was studied in batch culture following exposure of cells to low concentrations of monochlorophenol, pentachlorophenol and cadmium chloride. Changes in protein patterns were identified after pulse-chase labelling of proteins with [35S]methionine and subsequent two-dimensional gel electrophoresis (2D-PAGE). We demonstrated that besides the induction of some stress proteins, also a transient decrease in the rate of synthesis of other proteins occurred. Two of these proteins were identified as OmpF and aspartate transcarbamoylase (ATCase). Their transient repression appeared to be a general response to stress elicited by different pollutants and may therefore be used as a general and sensitive early warning system for pollutant stress

Benzene degradation by Ralstonia pickettii PKO1 in the presence of the alternative substrate succinate

The regulation of benzene degradation by Ralstonia pickettii PKO1 in the presence of the alternative substrate succinate was investigated in batch and continuous culture. In batch culture, R. pickettii PKO1 achieved a maximum specific growth rate with benzene of 0.18h−1, while succinate allowed much faster growth (μmax=0.5h−1). Under carbon excess conditions succinate repressed benzene consumption resulting in diauxic growth whereas under carbon-limited conditions in the chemostat both substrates were used simultaneously. Moreover, the effect of succinate on the adaptation towards growth with benzene was investigated in carbon-limited continuous culture at a dilution rate of 0.1h−1 by changing the inflowing carbon substrate from succinate to different mixtures of benzene and succinate. The adaptation process towards utilisation of benzene was rather complex. Three to sevenhours after the medium shift biomass production from benzene started. Higher proportions of succinate in the mixture had a positive effect on both the onset of biomass production and on the time required for induction of benzene utilisation. Strikingly, after the initial increase in biomass and benzene-catabolising activities, the culture collapsed regularly and wash-out of biomass was observed. After a transient phase of low biomass concentrations growth on benzene resumed so that finally rather stable and high biomass concentrations were reached. The decrease in biomass and degradative activities cannot be explained so far, but the possibilities of either intoxication of the cells by benzene itself, or of inhibition by degradation intermediates were ruled ou

Metabolites and dead-end products from the microbial oxidation of quaternary ammonium alcohols

Methyl-triethanol-ammonium originates from the hydrolysis of the parent esterquat surfactant, which is used as softener in fabric care. The initial steps of the catabolism were investigated in cell-free extracts of the bacterial strain MM 1 able to grow with methyl-triethanol-ammonium as sole source of carbon, energy and nitrogen. The initial degradation of methyl-triethanol-ammonium is an enzymatically catalyzed reaction, located in the particulate fraction of strain MM 1. The oxygen dependent reaction occurred also in presence of phenazine methosulfate as an alternative electron acceptor. As soon as one ethanol group of methyl-triethanol-ammonium was oxidized to the aldehyde, cyclic hemiacetals were formed by intramolecular cyclization. The third ethanol group of methyl-triethanol-ammonium was oxidized to the aldehyde and the carboxylic acid sequentially. The structurally related compounds dimethyl-diethanol-ammonium and choline were oxidized as well, whereas (±)-2,3-dihydroxypropyl-trimethyl-ammonium was not converted at all. The structures of the metabolites were established by 1D and 2D 1H, 13C and 14N NMR spectroscopy and by capillary electrophoresis mass spectrometr

In vitro transcription profiling of the σS subunit of bacterial RNA polymerase: re-definition of the σS regulon and identification of σS-specific promoter sequence elements

Specific promoter recognition by bacterial RNA polymerase is mediated by σ subunits, which assemble with RNA polymerase core enzyme (E) during transcription initiation. However, σ70 (the housekeeping σ subunit) and σS (an alternative σ subunit mostly active during slow growth) recognize almost identical promoter sequences, thus raising the question of how promoter selectivity is achieved in the bacterial cell. To identify novel sequence determinants for selective promoter recognition, we performed run-off/microarray (ROMA) experiments with RNA polymerase saturated either with σ70 (Eσ70) or with σS (EσS) using the whole Escherichia coli genome as DNA template. We found that Eσ70, in the absence of any additional transcription factor, preferentially transcribes genes associated with fast growth (e.g. ribosomal operons). In contrast, EσS efficiently transcribes genes involved in stress responses, secondary metabolism as well as RNAs from intergenic regions with yet-unknown function. Promoter sequence comparison suggests that, in addition to different conservation of the −35 sequence and of the UP element, selective promoter recognition by either form of RNA polymerase can be affected by the A/T content in the −10/+1 region. Indeed, site-directed mutagenesis experiments confirmed that an A/T bias in the −10/+1 region could improve promoter recognition by Eσ