Influence of algal organic matter on Escherichia coli behaviour

International audienceThis study was undertaken after a report of drinking water industries which suggested the existence of a relation between algal proliferation (algal bloom) in resource water and coliform non-conformity in distribution networks. Our objective was thus to estimate if algal organic matter (AOM) could be used as a substrate by E. coli and explain its resuscitation in drinking water. For this purpose, E. coli was inoculated in sterile dechlorinated drinking water supplemented with organic matter of various origins in order to reach +0.2 (±0.1) mg BDOC L−1 (AOM, glucose or acetate). The results showed that the addition of AOM (naturally secreted by algae or released after a chlorine or ozone stress) in drinking water can represent a risk for water biological stability: indeed, AOM allowed either a higher cellular production, or a better maintenance of cultivability of E. coli than those observed in non-supplemented sterile drinking water, glucose or acetate solutions (in spite of equivalent additions of BDOC). Growth of E. coli was even up to 10 times higher in the presence of AOM coming from ozonated algae

Escherichia coli Behavior in the Presence of Organic Matter Released by Algae Exposed to Water Treatment Chemicals

When exposed to oxidation, algae release dissolved organic matter with significant carbohydrate (52%) and biodegradable (55 to 74%) fractions. This study examined whether algal organic matter (AOM) added in drinking water can compromise water biological stability by supporting bacterial survival. Escherichia coli (1.3 × 10(5) cells ml(−1)) was inoculated in sterile dechlorinated tap water supplemented with various qualities of organic substrate, such as the organic matter coming from chlorinated algae, ozonated algae, and acetate (model molecule) to add 0.2 ± 0.1 mg of biodegradable dissolved organic carbon (BDOC) liter(−1). Despite equivalent levels of BDOC, E. coli behavior depended on the source of the added organic matter. The addition of AOM from chlorinated algae led to an E. coli growth equivalent to that in nonsupplemented tap water; the addition of AOM from ozonated algae allowed a 4- to 12-fold increase in E. coli proliferation compared to nonsupplemented tap water. Under our experimental conditions, 0.1 mg of algal BDOC was sufficient to support E. coli growth, whereas the 0.7 mg of BDOC liter(−1) initially present in drinking water and an additional 0.2 mg of BDOC acetate liter(−1) were not sufficient. Better maintenance of E. coli cultivability was also observed when AOM was added; cultivability was even increased after addition of AOM from ozonated algae. AOM, likely to be present in treatment plants during algal blooms, and thus potentially in the treated water may compromise water biological stability

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Barcode data used to generate Fig. S

Data from: DNA barcoding reveals a largely unknown fauna of Gracillariidae leaf-mining moths in the Neotropics

Higher taxa often show increasing species richness towards tropical low latitudes, a pattern known as the latitudinal biodiversity gradient (LBG). A rare reverse LBG (with greater richness towards temperate high latitudes) is exhibited by Gracillariidae leaf-mining moths, in which most described species occur in northern temperate areas. We carried out the first assessment of gracillariid species diversity in two Neotropical regions to test whether the relatively low tropical species diversity of this family is genuine or caused by insufficient sampling and a strong taxonomic impediment. Field surveys in six French Guianan and one Ecuadorian site produced 516 gracillariid specimens that were DNA barcoded to facilitate identification and to match larvae inside leaf mines with adults. Species delineation from sequence data was approximated using Automatic Barcode Gap Discovery and Refined Single Linkage Analysis through the Barcode Index Number system, and the proportion of described/undescribed species was estimated after comparison with types of 83% of described species. Locally, alpha-diversity far exceeds that of any known temperate fauna, with as many as 108 candidate species (59.3% as singletons) collected at one site, and with an estimated species richness lower bound of 240 species. Strikingly, at least 85% of the species collected as adults were found to be undescribed. Our sampling represents the most thorough survey of gracillariid species diversity in the Neotropics to date and the results from both our molecular and morphological analyses indicate that the current reverse LBG seen in this group is an artefact of insufficient sampling and a strong description deficit in the Neotropics

Increased choroidal thickness: a new feature to monitor age-related macular degeneration recurrence

cited By 0Purpose: The main objective of this study was to assess choroidal thickness (CT) changes during an exudative recurrence of age-related macular degeneration (AMD). Methods: A real-life prospective non-interventional 9-month study was conducted in two centers in consecutive patients with exudative AMD between November 2016 and July 2017. CT was measured manually in both eyes based on enhanced-depth imaging spectral-domain optical coherence tomography at different follow-up visits scheduled in the morning. Results: A total of 134 patients were included. Ninety-five patients presented at least one episode, defined by a follow-up visit under controlled condition (dry retina) followed by a visit for exudative recurrence. A total of 119 episodes were analyzed. The mean CT change in the treated eye was + 8.45 ± 13.52 μm (p < 0.001) and + 5.62 ± 14.77 μm (p = 0.009) respectively in the subfoveal area and nasal area. No significant change in CT was observed in the fellow eye. No significant association between CT changes and treatment, number of intravitreal injections, and blood pressure was observed. Conclusion: CT increased in case of exudative recurrence of neovascular AMD. The increase was mild but significant. Thus, CT could be used as a monitoring criterion, like the central retinal thickness, in AMD management. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature