"Access to safe water is a fundamental human need and therefore a basic human right" --Kofi Annan, United Nations Secretary General Edited by two world-renowned scientists in the field, The Handbook ...of Water and Wastewater Microbiology provides a definitive and comprehensive coverage of water and wastewater microbiology. With contributions from experts from around the world, this book gives a global perspective on the important issues faced in the provision of safe drinking water, the problems of dealing with aquatic pollution and the processes involved in wastewater management. Starting with an introductory chapter of basic microbiological principles, The Handbook of Water and Wastewater Microbiology develops these principles further, ensuring that this is the essential text for process engineers with little microbiological experience and specialist microbiologists alike. * Comprehensive selection of reviews dealing with drinking water and aquatic pollution * Provides an understading of basic microbiology and how it is applied to engineering process solutions * Suitable for all levels of knowledge in microbiology -from those with no background to specialists who require the depth of information
This article is about differences between, and the adequacy of, response rates to online and paper-based course and teaching evaluation surveys. Its aim is to provide practical guidance on these ...matters. The first part of the article gives an overview of online surveying in general, a review of data relating to survey response rates and practical advice to help boost response rates. The second part of the article discusses when a response rate may be considered large enough for the survey data to provide adequate evidence for accountability and improvement purposes. The article ends with suggestions for improving the effectiveness of evaluation strategy. These suggestions are: to seek to obtain the highest response rates possible to all surveys; to take account of probable effects of survey design and methods on the feedback obtained when interpreting that feedback; and to enhance this action by making use of data derived from multiple methods of gathering feedback.
The epidermal patterning factor (EPF) family of secreted signaling peptides regulate the frequency of stomatal development in model dicot and basal land plant species. Here, we identify and ...manipulate the expression of a barley (Hordeum vulgare) ortholog and demonstrate that when overexpressed HvEPF1 limits entry to, and progression through, the stomatal development pathway. Despite substantial reductions in leaf gas exchange, barley plants with significantly reduced stomatal density show no reductions in grain yield. In addition, HvEPF1OE barley lines exhibit significantly enhanced water use efficiency, drought tolerance, and soil water conservation properties. Our results demonstrate the potential of manipulating stomatal frequency for the protection and optimization of cereal crop yields under future drier environments.
Endosymbiosis allows hosts to acquire new functional traits such that the combined host and endosymbiont can exploit vacant ecological niches and occupy novel environments 1, 2; consequently, ...endosymbiosis affects the structure and function of ecosystems 3, 4. However, for many endosymbioses, it is unknown whether their evolutionary basis is mutualism or exploitation 5–9. We estimated the fitness consequences of symbiosis using the interaction between the protist host Paramecium bursaria and the algal symbiont Chlorella sp. 10. Host fitness was strongly context dependent: whereas hosts benefited from symbiosis at high light intensity, carrying endosymbionts was costly to hosts in the dark and conferred no benefit over growing autonomously at intermediate light levels. Autonomous Chlorella densities increased monotonically with light intensity, whereas per-host symbiont load and symbiont abundance peaked at intermediate light levels and were lowest at high light intensity. This suggests that hosts controlled the costs of symbiosis by manipulating symbiont load according to light intensity. Photosynthetic efficiency was consistently lower for symbiotic compared to autonomous algae, suggesting nutritional constraints upon algae in symbiosis. At intermediate light levels, we observed the establishment of small populations of free-living algae alongside the hosts with endosymbionts, suggesting that symbionts could escape symbiosis, but only under conditions where hosts didn’t benefit from symbiosis. Together, these data suggest that hosts exerted strong control over endosymbionts and that there were no conditions where this nutritional symbiosis was mutually beneficial. Our findings support theoretical predictions (e.g., 5, 9) that controlled exploitation is an important evolutionary pathway toward stable endosymbiosis.
•For protozoa and their algal symbionts, fitness in symbiosis is context dependent•Symbiosis changes from costly to beneficial for hosts with increasing light•Symbiosis is always costly for algae whose interests do not align with the host’s•Evolutionary stability of the symbiosis results from exploitation not mutualism
Lowe et al. show that a photosynthetic symbiosis between an algal symbiont and a protist host is based on exploitation of symbionts by the host, not mutual benefit. Symbiosis becomes more beneficial for hosts with increasing light, but more costly for symbionts, such that the fitness interests of the interacting species do not align.
Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants, but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the ...symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilization has been shown to elicit strong mutualism, characterized by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a 15N‐labelled, nitrogen‐rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Furthermore, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant.
When granted access to an organic matter patch, arbuscular mycorrhizal fungi were found to obtain significant amounts of nitrogen (N) from the patch and transfer a substantial amount to their partner plant. The patch‐derived N contributed significantly to, and increased, total plant N. Total plant phosphorus (P) increased also, as did total plant mass. This study is the first to demonstrate simultaneous increases in N, P and biomass of plants with arbuscular mycorrhizal hyphal access to a patch of organic matter.
The concept of iso‐ vs. anisohydry has been used to describe the stringency of stomatal regulation of plant water potential (ψ). However, metrics that accurately and consistently quantify species’ ...operating ranges along a continuum of iso‐ to anisohydry have been elusive. Additionally, most approaches to quantifying iso/anisohydry require labour‐intensive measurements during prolonged drought. We evaluated new and previously developed metrics of stringency of stomatal regulation of ψ during soil drying in eight woody species and determined whether easily‐determined leaf pressure–volume traits could serve as proxies for their degree of iso‐ vs. anisohydry. Two metrics of stringency of stomatal control of ψ, (1) a ‘hydroscape’ incorporating the landscape of ψ over which stomata control ψ, and (2) the slope of the daily range of ψ as pre‐dawn ψ declined, were strongly correlated with each other and with the leaf osmotic potential at full and zero turgor derived from pressure–volume curves.
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