Soil Berms as an Alternative to Steel Plate Borders for Runoff Plots

ABSTRACT 2000), reducing soil surface sealin

The influence of external factors on bacteriophages—review

The ability of bacteriophages to survive under unfavorable conditions is highly diversified. We summarize the influence of different external physical and chemical factors, such as temperature, acidity, and ions, on phage persistence. The relationships between a phage’s morphology and its survival abilities suggested by some authors are also discussed. A better understanding of the complex problem of phage sensitivity to external factors may be useful not only for those interested in pharmaceutical and agricultural applications of bacteriophages, but also for others working with phages

Waterborne microbial risk assessment : a population-based dose-response function for Giardia spp. (E.MI.R.A study)

BACKGROUND: Dose-response parameters based on clinical challenges are frequently used to assess the health impact of protozoa in drinking water. We compare the risk estimates associated with Giardia in drinking water derived from the dose-response parameter published in the literature and the incidence of acute digestive conditions (ADC) measured in the framework of an epidemiological study in a general population. METHODS: The study combined a daily follow-up of digestive morbidity among a panel of 544 volunteers and a microbiological surveillance of tap water. The relationship between incidence of ADC and concentrations of Giardia cysts was modeled with Generalized Estimating Equations, adjusting on community, age, tap water intake, presence of bacterial indicators, and genetic markers of viruses. The quantitative estimate of Giardia dose was the product of the declared amount of drinking water intake (in L) by the logarithm of cysts concentrations. RESULTS: The Odds Ratio for one unit of dose [OR = 1.76 (95% CI: 1.21, 2.55)] showed a very good consistency with the risk assessment estimate computed after the literature dose-response, provided application of a 20 % abatement factor to the cysts counts that were measured in the epidemiological study. Doing so, a daily water intake of 2 L and a Giardia concentration of 10 cysts/100 L, would yield an estimated relative excess risk of 12 % according to the Rendtorff model, against 11 % when multiplying the baseline rate of ADC by the corresponding OR. This abatement parameter encompasses uncertainties associated with germ viability, infectivity and virulence in natural settings. CONCLUSION: The dose-response function for waterborne Giardia risk derived from clinical experiments is consistent with epidemiological data. However, much remains to be learned about key characteristics that may heavily influence quantitative risk assessment results

Renewable energy from Cyanobacteria: energy production optimization by metabolic pathway engineering

The need to develop and improve sustainable energy resources is of eminent importance due to the finite nature of our fossil fuels. This review paper deals with a third generation renewable energy resource which does not compete with our food resources, cyanobacteria. We discuss the current state of the art in developing different types of bioenergy (ethanol, biodiesel, hydrogen, etc.) from cyanobacteria. The major important biochemical pathways in cyanobacteria are highlighted, and the possibility to influence these pathways to improve the production of specific types of energy forms the major part of this review

Degradation of the Poliovirus 1 genome by chlorine dioxide

International audienceAims: This study was undertaken to gain an understanding of the factors that influence viral RNA degradation in the presence of chlorine dioxide (ClO2), which will be very useful in helping to define the significance of the presence of the viral genome in disinfected water.Methods and Results: We focused our investigation on the influence of ClO2 on extracted RNA on the one hand, and on the infectious virus on the other. Our first results show that RNA degradation, like viral inactivation, is dose dependent. The influence of the spatial organization of the targeted genomic sequence, as well as that of its size and location (and/or sequence) on degradation of the Poliovirus 1 genome by ClO2, was studied using real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR). The results show that the preferential sites of action of ClO2 appear to be located in the untranslated regions, 5′‐ and 3′‐UTR, a phenomenon influenced by both the presence of secondary structures and the genomic sequence in these regions. Our results also reveal a rapid decrease of infectious particles quantified by the cell culture for the applied dose. Comparison between cell culture and real‐time PCR for viral detection reveals disagreement following disinfection treatment, even for the largest targeted fragment (a 6989‐base fragment representing the quasi‐whole viral genome).Conclusions: The detection of genome fragments is insufficient to confirm the presence of the infectious virus, as each targeted fragment shows a different sensitivity. Hence, the smallest targeted fragment (76 bp) persisted throughout the analysis period, while the longest targeted fragment (6989 bp) disappeared very rapidly. Highly sensitive regions (i.e. 5′‐ and 3′‐UTR) should be targeted to avoid an overestimation of the risk of viral infection using molecular biology methods in water following disinfection. Further studies in this area are needed.Significance and Impact of the Study: To date, it has not been possible to routinely apply virological controls to drinking water because of the time‐consuming nature of the gold standard technique (cell culture) and its inability to detect all serotypes (e.g. Norovirus). Molecular techniques (e.g. real‐time RT‐PCR) constitute a solution to the rapid and specific detection of all the serotypes. However, ignorance of the mechanisms of viral degradation prevents the validation of PCR for the measurement of the risk of infection to humans following disinfection treatment

Effects of pH on plaque forming unit counts and aggregation of MS2 bacteriophage

International audienceAim: The aim of this study was to determine whether aggregation processes in aqueous phase may explain the decrease in plaque forming unit (PFU) counts for pH close to the isoelectric point (pI) of viral particles (MS2 phages).Methods and Results: Loss in PFU was observed for pH ≤ pI (pIMS2 = 3·9): for example, at pH 2·5, loss was approx. 3 log10 PFU. Particle size analysis combining results of dynamic light scattering and flow particle image analysis was then applied to determine the aggregate state of viral suspensions by recording size distributions. The size of major population significantly changed to 30 nm at neutral pH to more than several micrometres when passing below the isoelectric point.Conclusions: Our study shows that MS2 phages exhibit significant aggregation processes for pH ≤ pI leading to aggregate with sizes of few micrometres. This aggregation process can largely explain the decline in PFU counts.Significance and Impact of the Study: It is clear that viral aggregation can be a source of significant bias for PFU assays because in the presence of an aggregate the PFU count can be less than the sum of its constituent particles. Therefore, cautions should be taken in terms of conditions of storage (pH far from pI) to avoid such aggregation artefact

Les biofilms des systèmes de distribution d'eau potable : un réservoir potentiel de pathogènes ?

International audienc

Estimating Giardia cyst viability using RT-PCR

International audienceThe aim of this work was to evaluate the use of molecular techniques for the detection of viable Giardia cysts in the environment to assess public health issues. Three target genes were selected: the heat shock protein gene, HSP70, which is expressed in response to stress; the giardin gene, which encodes a structural protein; and, alcohol dehydrogenase E (ADHE), a novel gene encoding an enzyme involved in the metabolism of energy. We tested the efficiency of five protocols for the extraction of either genomic DNA or total RNA from Giardia cysts: two of these protocols were previously cited in the literature and three consisted of commercial DNA extraction kits. The brands of enzyme were determined according to the primers chosen and the amplification conditions were optimised: 2.5 mM MgCl2, 0.5 mM primers and 60°C for annealing temperature. A semi-nested PCR method and an RT semi-nested PCR procedure were developed to detect mRNA from these three genes and to estimate the viability of Giardia cysts