The PlcR Virulence Regulon of Bacillus cereus

PlcR is a Bacillus cereus transcriptional regulator, which activates gene expression by binding to a nucleotidic sequence called the ‘PlcR box’. To build a list of all genes included in the PlcR regulon, a consensus sequence was identified by directed mutagenesis. The reference strain ATCC14579 sequenced genome was searched for occurrences of this consensus sequence to produce a virtual regulon. PlcR control of these genes was confirmed by comparing gene expression in the reference strain and its isogenic Δ-plcR strain using DNA microarrays, lacZ fusions and proteomics methods. The resulting list included 45 genes controlled by 28 PlcR boxes. Forty of the PlcR controlled proteins were exported, of which 22 were secreted in the extracellular medium and 18 were bound or attached to cell wall structures (membrane or peptidoglycan layer). The functions of these proteins were related to food supply (phospholipases, proteases, toxins), cell protection (bacteriocins, toxins, transporters, cell wall biogenesis) and environment-sensing (two-component sensors, chemotaxis proteins, GGDEF family regulators). Four genes coded for cytoplasmic regulators. The PlcR regulon appears to integrate a large range of environmental signals, including food deprivation and self cell-density, and regulate the transcription of genes designed to overcome obstacles that hinder B. cereus growth within the host: food supply, host barriers, host immune defenses, and competition with other bacterial species. PlcR appears to be a key component in the efficient adaptation of B. cereus to its host environment

Necrotrophism Is a Quorum-Sensing-Regulated Lifestyle in Bacillus thuringiensis

How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading

Principles for the design of a policy framework to address product life cycle impacts

Introduction: Product-oriented environmental law is an expanding, poly-thematic subsection of environmental law. First, an increasing number of policy instruments are being used at the international, European and national levels to regulate products, including mandatory performance standards, consumer subsidies, public procurement practices, product bans, taxes and charges and various kinds of mandatory and voluntary labelling schemes. Second, the policies cover an increasing range of environmental issues and life cycle phases, including product chemical content, requirements regarding collection and recycling, energy efficiency, bio-based materials, durability and lifetime performance, conflict minerals and working conditions. These policies can work in synergy and interact well, or they can contradict each other in various ways. It depends both on the policy design, but also on how the policies are applied. There are various ideas on (1) how these policies should work together in a policy mix and (2) how their interaction can be improved. Maitre-Ekern has outlined some important principles behind choice of policies for product policy, and concluded that a policy mix is required due to the inherent limitations of specific policy instruments to contribute to the changes needed. There are, however, very few examples of these principles being applied and lessons being learned in the ‘law and economics’ field with regard to ‘design’ principles or approaches to an appropriate policy mix. This contribution aims to redress these deficiencies by making a preliminary attempt to apply elements not only from this area of the literature, but other legal research as well, to product regulation. We concentrate on European law, i.e. EU laws as well as relevant Member State initiatives. This is explained by the book’s European focus, but also because (1) the EU is the main global standard-setter for product regulation and often has the most stringent standards compared to, e.g., the US and Japan and (2) other jurisdictions often apply EU standards. As Bradford has shown, the US and other jurisdictions tend to comply in practice with many EU laws in the absence of relevant US regulations

Biologically mediated phosphorus precipitation in wastewater treatment with microalgae

A lab-scale continuous microalgal culture was grown on sterile-filtered wastewater in order to clarify the phosphorus removing mechanisms in a microalgal treatment step that treats residual phosphorus from a hydroponic wastewater treatment pilot plant. The phosphorus assimilation was dependent on algal biomass production, whereas the chemical precipitation was dependent on phosphorus load, i.e. an increase in average precipitation rate with decreased hydraulic retention time was observed. The chemical precipitation was mainly a result of the increased pH, which was biologically mediated by the photosynthesising algae. The precipitate was composed of a calcium phosphate with magnesium included, magnesium hydroxide and calcite. A significant nitrogen removal was also experienced, which implies that the microalgal wastewater treatment is appropriate both for phosphorus and nitrogen removal