The influence of substrate kinetics on the microbial community structure in granular anaerobic biomass

The development of a strong, active granular sludge bed is necessary for optimal operation of upflow anaerobic sludge blanket reactors. The microbial and mechanical structure of the granules may have a strong influence on desirable properties such as growth rate, settling velocity and shear strength. Theories have been proposed for granule microbial structure based on the relative kinetics of substrate degradation, but contradict some observations from both modelling and microscopic studies. In this paper, the structures of four granule types were examined from full-scale UASB reactors, treating wastewater from a cannery, a slaughterhouse, and two breweries. Microbial structure was determined using fluorescence in situ hybridisation probing with 16S rRNA-directed oligonucleotide probes, and superficial structure and microbial density (volume occupied by cells and microbial debris) assessed using scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The granules were also modelled using a distributed parameter biofilm model, with a previously published biochemical model structure, biofilm modelling approach, and model parameters. The model results reflected the trophic structures observed, indicating that the structures were possibly determined by kinetics. Of particular interest were results from simulations of the protein grown granules, which were predicted to have slow growth rates, low microbial density, and no trophic layers, the last two of which were reflected by microscopic observations. The primary cause of this structure, as assessed by modelling, was the particulate nature of the wastewater, and the slow rate of particulate hydrolysis, rather than the presence of proteins in the wastewater. Because solids hydrolysis was rate limiting, soluble substrate concentrations were very low (below Monod half saturation concentration), which caused low growth rates. (C) 2003 Elsevier Ltd. All rights reserved.

Adaptive responses of wild mungbean (Vigna radiata ssp sublobata) to photo-thermal environment. II. Growth, biomass, and seed yield

The leaf growth, dry matter production, and seed yield of 11 wild mungbean ( Vigna radiata ssp. sublobata) accessions of diverse geographic origin were observed under natural and artificial photoperiod temperature conditions, to determine the extent to which genotypic differences could be attributed to adaptive responses to photo-thermal environment. Environments included serial sowings in the field in SE Queensland, complemented by artificial photoperiod extension and controlled-environment growth rooms. Photo-thermal environment influenced leaf growth, total dry matter production ( TDM), and seed yield directly, through effects of ( mainly cool) temperature on growth, and indirectly, through effects on phenology. In terms of direct effects, leaf production, leaf expansion, and leaf area were all sensitive to temperature, with implied base temperatures higher than usually observed in cultivated mungbean ( V. radiata ssp. radiata). Genotypic sensitivity to temperature varied systematically with accession provenance and appeared to be of adaptive significance. In terms of the indirect effects of photo-thermal environment, genotypic and environmental effects on TDM were positively related to changes in total growth duration, and harvest index was negatively related to the period from sowing to flowering, similar to cultivated mungbean. However, seed yield was positively related to the duration of reproductive growth, reflecting the indeterminate growth habit of the wild accessions. As a consequence, the wild accessions are more responsive to favourable environments than typically observed in cultivated mungbean, which is determinate in habit. It is suggested that the introduction of the indeterminate trait into mungbean from the wild subspecies would increase the responsiveness of mungbean to favourable environments, analogous to that of black gram ( V. mungo). Although the wild subspecies appeared more sensitive to cool temperature than cultivated mungbean, it may provide a source of tolerance to the warmer temperatures experienced during the wet season in the tropics.

Construction and analysis of a metagenomic library from an enhanced biological phosphorus removal biomass

The enhanced biological phosphorus removal (EBPR) process is regularly used for the treatment of wastewater, but suffers from erratic performance. Successful EBPR relies on the growth of bacteria called polyphosphate-accumulating organisms (PAOs), which store phosphorus intracellularly as polyphosphate, thus removing it from wastewater. Metabolic models have been proposed which describe the measured chemical transformations, however genetic evidence is lacking to confirm these hypotheses. The aim of this research was to generate a metagenomic library from biomass enriched in PAOs as determined by phenotypic data and fluorescence in situ hybridisation (FISH) using probes specific for the only described PAO to date, Candidatus Accumulibacter phosphatis. DNA extraction methods were optimised and two fosmid libraries were constructed which contained 93 million base pairs of metagenomic data. Initial screening of the library for 16S rRNA genes revealed fosmids originating from a range of non-pure-cultured wastewater bacteria. The metagenomic libraries constructed will provide the ability to link phylogenetic and metabolic data for bacteria involved in nutrient removal from wastewater. Keywords DNA extraction; EBPR; metagenomic library; 16S rRNA gene.

Nitrogen, phosphorus, silica, and carbon in Moreton Bay, Queensland, Australia: Differential limitation of phytoplankton biomass and production

Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus (P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over 3 seasons in 1997-1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all regions, both the dissolved nutrients and particulate biomass yielded N : P ratios < 6 and N : Si ratios < 1. Both relationships suggest strong limitation of biomass by N throughout the bay. Limitation of rates of nutrient uptake and productivity were more complex. Low C : N and C : P uptake ratios at the riverine site suggested light limitation at all seasons, low N : P ratios suggested some degree of N limitation and high N : Si uptake ratios in austral winter suggested Si limitation of uptake during that season only. No evidence of P limitation of biomass or productivity was evident.

Nature-based tourism and the valuation of its environmental resources: Economic and other aspects

Nature-based tourism has grown in importance in recent decades, and strong links have been established between it and ecotourism. This reflects rising incomes, greater levels of educational attainment and changing values, especially in the Western world. Nature-based tourism is quite varied. Different types of such tourism are identified and their consequences for sustainability of their resource-base are briefly considered. The development and management of nature-based tourism involves many economic aspects, several of which are discussed. For example, one must consider the economics of reserving or protecting land for this type of tourism. What economic factors should be taken into account? Economists stress the importance of taking into account the opportunity costs involved in such a decision. This concept is explained. However, determining the net economic value of an area used for tourism is not straightforward. Techniques for doing this, such as the travel cost method and stated value methods, are introduced. Natural areas reserved for tourism may have economic value not only for tourism but also jointly for other purposes, such as conserving wildlife, maintaining hydrological cycles and so on. These other purposes, should be taken into account when considering the use of land for nature-based tourism. According to one economic point of view, land should be used in a way that maximises its total economic value. While this approach has its merits, it does not take into account the distribution of benefits from land use and its local impacts on income and employment. These can be quite important politically and for nature conservation, and are discussed. Finally, there is some discussion of whether fees charged to tourists for access to environmental resources should discriminate between domestic tourists and foreigners.

Parental reactions to infant death: The effects of resources and coping strategies

The aim of this research was to examine, from a stress and coping perspective, the effects of resources (both personal and environmental) and coping strategies on parental reactions to infant death. One hundred and twenty-seven parents (60 fathers, 67 mothers) participated in the study. The predictors of parental distress (background factors, resources, coping methods) were initially assessed at 4-6 weeks post-loss. Parental distress (assessed using a composite measure of psychiatric disturbance, physical symptoms, and perinatal grief) was further assessed at 6 months post-loss and at 15 months postloss. After control for the stability in adjustment across time, there was consistent evidence that higher levels of education were associated with lower levels of parental distress over time. Among mothers, the number of friends in whom mothers had the confidence to confide emerged as a positive predictor of adjustment to infant death. A reliance on problem-focused coping was associated with greater maternal distress at 6 months post-loss, whereas coping by seeking support was associated with less distress at 15 months post-loss. There is no evidence that background factors and resources influenced parental distress through coping.

Patents and the CGIAR system of International Agricultural Research Centres' germplasm collections under the International Treaty on Plant Genetic Resources for Food and Agriculture

A key controversy in negotiating the International Treaty on Plant Genetic Resources for Food and Agriculture, and the likely long-term effectiveness of the agreement, is the way in which the intellectual property provisions are interpreted and applied to the key genetic resources forming the Consultative Group on International Agricultural Research (CGIAR) system of International Agricultural Research Centres' (IARC) collections. This paper reviews the intellectual property provisions in the treaty and examines the likely consequences from patenting under the Patents Act 1990 over materials derived from these collections. The consequence is argued to be significant and, over time, these practices are likely to deplete the usefulness of these collections and undermine the relevance of the treaty. The paper concludes that Australia's interests might best be served by arguing that access to these collections, and the other materials under the treaty, be subject to a non-exclusive, royalty free licence for any use of the derived materials to develop useful new plant varieties.

Cell cycle model to describe animal cell size variation and lag between cell number and biomass dynamics

The use of cell numbers rather than mass to quantify the size of the biotic phase in animal cell cultures causes several problems. First, the cell size varies with growth conditions, thus yields expressed in terms of cell numbers cannot be used in the normal mass balance sense. Second, experience from microbial systems shows that cell number dynamics lag behind biomass dynamics. This work demonstrates that this lag phenomenon also occurs in animal cell culture. Both the lag phenomenon and the variation in cell size are explained using a simple model of the cell cycle. The basis for the model is that onset of DNA synthesis requires accumulation of G1 cyclins to a prescribed level. This requirement is translated into a requirement for a cell to reach a critical size before commencement of DNA synthesis. A slower gl-owing cell will spend more time in G1 before reaching the critical mass. In contrast, the period between onset of DNA synthesis and mitosis, tau(B), is fixed. The two parameters in the model, the critical size and tau(B), were determined from eight steady-state measurements of mean cell size in a continuous hybridoma culture. Using these parameters, it was possible to predict with reasonable accuracy the transient behavior in a separate shift-up culture, i.e., a culture where cells were transferred from a lean environment to a rich environment. The implications for analyzing experimental data for animal cell culture are discussed. (C) 1997 John Wiley & Sons, Inc.