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Thabet S.,CNRS Research on Catalysis and Environment in Lyon | Thabet S.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Weiss-Gayet M.,University Claude Bernard Lyon 1 | Dappozze F.,CNRS Research on Catalysis and Environment in Lyon | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2013

We have investigated the antimicrobial effects of photocatalysis on yeast (Saccharomyces cerevisiae), an essential eukaryotic unicellular model of living cells. As compared to UV-A irradiation, photocatalytic inactivation kinetics revealed a faster microbial cell cultivability inactivation. Optimal experimental conditions required a semiconductor concentration of 0.1g/l with 3.8mW/cm2 UV-A radiance intensity. Cell viability was monitored by plasma membrane permeability and loss of enzymatic activity using double fluorescent dye staining and flow cytometry. Plasma membrane permeability and enzymatic activity were almost simultaneously targeted. Esterase enzymatic activity decreased progressively, suggesting that the intracellular protein pool was sequentially damaged by the treatment. In yeast cells, the presence of a thick cell wall did not prevent the plasma membrane from being a prime photocatalytic target. Monitoring of chemical byproducts confirmed the loss of membrane integrity. A massive loss of potassium, major cation in yeast, that was released first and in large amounts, remained constant beyond 5h of treatment and was correlated to the number of damaged membrane-cells. On the contrary, ammonium ions concentration gradually increased, suggesting their generation through the photocatalytic process, probably via amino acid and protein degradation. Oxamic and oxalic acid that could also arise from damages to amino acids were detected. Amino acid analysis revealed a main component, increasing over time, corresponding to glycine. Glycine could be produced via the transformation of other amino acids, released from cell wall, membrane and intracellular proteins. © 2013 Elsevier B.V. Source

Vacher S.,Conidia | Hernandez C.,Conidia | Bartschi C.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Poussereau N.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis
Building and Environment | Year: 2010

Biocide-free and biocide-treated plasterboards as well as aluminum plate as a reference material normally considered as being insensitive to mould growth have been used as substrate to check the influence of different common wall coverings, i.e. paints and wall papers, on fungal growth. The results described in this paper show that any non-biodegradable material (such as aluminum) can become a substrate to fungal infestation once painted or wall paper applied, depending on the type of paint or wall paper used. Moreover, a biodegradable material treated with a biocide (biocide-treated plasterboard) offers partial resistance to fungal growth at a biodegradable surface covering. The main conclusion of this study is that composition of the surface covering applied on building materials is as important as the substrate itself when considering the bioreceptivity of this material to potential fungal infestation. Accordingly, any discussion on the ability of a given building material to resist or not to fungal infestation must refer to the exact composition of the surface covering (paint, varnish, wall paper, etc). This has not often been the case in many of the previous studies published on the topic. © 2009 Elsevier Ltd. All rights reserved. Source

Regoudis E.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Pelandakis M.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis
Experimental Parasitology | Year: 2016

The amoeba-flagellate Naegleria fowleri is a causative agent of primary amoebic meningoencephalitis (PAM). This thermophilic species occurs worldwide and tends to proliferate in warm aquatic environment. The PAM cases remain rare but this infection is mostly fatal. Here, we describe a single copy region which has been cloned and sequenced, and was used for both conventional and real-time PCR. Targeting a single-copy DNA sequence allows to directly quantify the N. fowleri cells. The real-time PCR results give a detection limit of 1 copy per reaction with high reproducibility without the need of a Taqman probe. This procedure is of interest as compared to other procedures which are mostly based on the detection of multi-copy DNA associated with a Taqman probe. © 2015 Elsevier Inc. Source

Billon-Grand G.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Rascle C.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Droux M.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis | Rollins J.A.,University of Florida | Poussereau N.,CNRS Laboratory for Microbiology, Adaptation & Pathogenesis
Molecular Plant Pathology | Year: 2012

During pathogenesis on sunflower cotyledons, Botrytis cinerea and Sclerotinia sclerotiorum show a striking resemblance in symptom development. Based on pH change profiles, the colonization process of both fungi can be divided into two stages. The first stage is associated with a pH decrease, resulting from an accumulation of citric and succinic acids. The second stage is correlated with a pH increase, resulting from an accumulation of ammonia. In this article, we also report that oxalic acid is produced at the late stage of the colonization process and that ammonia accumulation is concomitant with a decrease in free amino acids in decaying tissues. Sclerotinia sclerotiorum produces eight-fold more oxalic acid and two-fold less ammonia than B.cinerea. Consequently, during sunflower cotyledon colonization by B.cinerea, pH dynamics differ significantly from those of S. sclerotiorum. Invitro assays support the inplanta results and show that decreases in pH are linked to glucose consumption. At different stages of the colonization process, expression profiles of genes encoding secreted proteases were investigated. This analysis highlights that the expression levels of the B. cinerea protease genes are higher than those of S. sclerotiorum. This work suggests that the overt similarities of S. sclerotiorum and B. cinerea symptom development have probably masked our recognition of the dynamic and potentially different metabolic pathways active during host colonization by these two necrotrophic fungi. © 2011 Bayer Crop Science. Molecular Plant Pathology © 2011 BSPP and Blackwell Publishing Ltd. Source

Pigeot-Remy S.,CNRS Research on Catalysis and Environment in Lyon | Pigeot-Remy S.,Ahlstrom | Simonet F.,CNRS Research on Catalysis and Environment in Lyon | Errazuriz-Cerda E.,Center Communications Dimagerie Of Laennec Cecil | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2011

In order to identify some of the potential bacterial targets, the effects of TiO2 nanoparticles on bacteria in aqueous suspension were assessed in the dark and under UV-A (λ>340nm) radiation exposure, using the microorganism model Escherichia coli K-12. Illumination was produced with a HPK 125W lamp and suspended TiO2 Degussa P-25 was used as the photocatalyst, absorbing all the incident UV-A radiations.The impact of the photocatalyst on the bacteria was investigated by monitoring cell cultivability, cell wall integrity and nucleic acid stability. The contact of TiO2 particles with bacteria in the dark increased the bacterial sensitivity to membrane-perturbing agents, suggesting an increase in outer membrane permeability. In contrast, the contact between SiO2 particles, with an average particle size similar to that of TiO2 P-25, and bacteria did not induce any alteration of the cell permeability. The TiO2 deleterious action on the envelope integrity continued during the UV-A radiations exposure. Impacts on bacterial permeability precede the total loss of cultivability. After 2.5h of photocatalytic treatment at 3.45mW/cm2, bacteria were no longer cultivable on their standard growth medium. However, some of them could become cultivable again under specific environmental conditions appropriate to their survival. These resilient bacteria exposed again to UV-A photocatalysis were more resistant to the treatment.Some chemical by-products released during photocatalytic inactivation of the bacteria were also monitored. The appearance of oxamic and oxalic acids as well as ammonium cations, sulfate and nitrate anions were observed. Transmission electron microscopy (TEM) was used to study the morphological damages to E. coli structure during the photocatalytic inactivation of the microorganisms. After 1.5. h of treatment, bacteria showed disorganized membrane structures, while bacteria were still visible although they were no longer cultivable after a longer exposure time. These results were correlated with damages of nucleic acids at in vivo level. An analysis by electrophoresis revealed that bacterial DNA and RNA molecules completely disappeared after 7 h of photocatalytic treatment. © 2011. Source

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