Global deletome profile of Saccharomyces cerevisiae exposed to lithium.

The increasing use of lithium (Li) in new technologies raises the question of its impact on living microorganisms. In the present study, we aimed to identify putative Li targets and resistance mechanisms in the yeast model Saccharomyces cerevisiae using a deletomic approach based on the screening of a collection of 4733 knockout mutants under Li exposure. This screening highlighted 60 mutants resistant to Li and 124 mutants sensitive to Li.

Influence of microorganisms on uranium release from mining-impacted lake sediments under various oxygenation conditions.

Microbial processes can be involved in the remobilization of uranium (U) from reduced sediments under O reoxidation events such as water table fluctuations. Such reactions could be typically encountered after U-bearing sediment dredging operations. Solid U(IV) species may thus reoxidize into U(VI) that can be released in pore waters in the form of aqueous complexes with organic and inorganic ligands.

Characterization of bacterial resistance in treated hospital wastewater.

This article seeks to characterize the bacterial profile of pediatric hospital wastewater samples collected at the outlet of a wastewater treatment plant, and to estimate their relative susceptibility to antimicrobial agents. A total of 64 strains were isolated in the wastewater samples, of which 49 were identified as belonging to different families: (e.g.

Simple or complex organic substrates inhibit arsenite oxidation and aioA gene expression in two β-Proteobacteria strains.

Microbial transformation of arsenic species and their interaction with the carbon cycle play a major role in the mobility of this toxic metalloid in the environment. The influence of simple or complex organic substrates on arsenic bio-oxidation was studied using two bacterial strains: one - the arsenivorans strain of Thiomonas delicata - is able to use AsIII as sole energy source; the other, Herminiimonas arsenicoxydans, is not. Experiments were performed at two AsIII concentrations (75 and 2 mg/L).

Pleiotropic effects of rfa-gene mutations on Escherichia coli envelope properties.

Mutations in the rfa operon leading to severely truncated lipopolysaccharide (LPS) structures are associated with pleiotropic effects on bacterial cells, which in turn generates a complex phenotype termed deep-rough. Literature reports distinct behavior of these mutants in terms of susceptibility to bacteriophages and to several antibacterial substances. There is so far a critical lack of understanding of such peculiar structure-reactivity relationships mainly due to a paucity of thorough biophysical and biochemical characterizations of the surfaces of these mutants.

Toxicity mechanisms of ZnO UV-filters used in sunscreens toward the model cyanobacteria Synechococcus elongatus PCC 7942.

Zinc oxide (ZnO) nanoparticles are commonly used in sunscreens for their UV-filtering properties. Their growing use can lead to their release into ecosystems, raising question about their toxicity. Effects of these engineered nanomaterials (ENMs) on cyanobacteria, which are important primary producers involved in many biogeochemical cycles, are unknown.

The Bacterial and Fungal Diversity of an Aged PAH- and Heavy Metal-Contaminated Soil is Affected by Plant Cover and Edaphic Parameters.

Industrial wasteland soils with aged PAH and heavy metal contaminations are environments where pollutant toxicity has been maintained for decades. Although the communities may be well adapted to the presence of stressors, knowledge about microbial diversity in such soils is scarce. Soil microbial community dynamics can be driven by the presence of plants, but the impact of plant development on selection or diversification of microorganisms in these soils has not been established yet.

Influence of organic matters on AsIII oxidation by the microflora of polluted soils.

The global AsIII-oxidizing activity of microorganisms in eight surface soils from polluted sites was quantified with and without addition of organic substrates. The organic substances provided differed by their nature: either yeast extract, commonly used in microbiological culture media, or a synthetic mixture of defined organic matters (SMOM) presenting some common features with natural soil organic matter. Correlations were sought between soil characteristics and both the AsIII-oxidizing rate constants and their evolution in accordance with inputs of organic substrates.

Impact of manufactured TiO2 nanoparticles on planktonic and sessile bacterial communities.

In the present study, we conducted a 2 week microcosm experiment with a natural freshwater bacterial community to assess the effects of titanium dioxide nanoparticles (TiO2-NPs) at various concentrations (0, 1, 10 and 100 mg/L) on planktonic and sessile bacteria under dark conditions. Results showed an increase of planktonic bacterial abundance at the highest TiO2-NP concentration, concomitant with a decrease from that of sessile bacteria. Bacterial assemblages were most affected by the 100 mg/L TiO2-NP exposure and overall diversity was found to be lower for planktonic bacteria and higher for sessile bacteria at this concentration.

Determination of physiological, taxonomic, and molecular characteristics of a cultivable arsenic-resistant bacterial community.

A collection of 219 bacterial arsenic-resistant isolates was constituted from neutral arsenic mine drainage sediments. Isolates were grown aerobically or anaerobically during 21 days on solid DR2A medium using agar or gelan gum as gelling agent, with 7 mM As(III) or 20 mM As(V) as selective pressure. Interestingly, the sum of the different incubation conditions used (arsenic form, gelling agent, oxygen pressure) results in an overall increase of the isolate diversity.

Ecotoxicological assessment of organic wastes spread on land: Towards a proposal of a suitable test battery.

The land spreading of organic wastes in agriculture is a common practice in Europe, under the regulation of the Directive 86/278/EEC. One of the objectives of this Directive is to prevent harmful effects of organic wastes on soil, plants and animals. Despite this regulatory framework, there is still a lack of harmonized ecotoxicological test strategy to assess the environmental hazard of such wastes.

The use of soil mites in ecotoxicology: a review.

Mites, and especially soil-inhabiting ones, have been less studied than the other invertebrates used in bio-assays for the assessment of soil quality and the hazards of chemicals, although these organisms are included in the regulatory assessment scheme of pesticides. The recent advances in the development of test methods for soil mites groups have provided more information on their sensitivities towards chemicals, which needs to be presented for a more robust assessment of the current trends in soil mite ecotoxicology. Moreover, interestingly mite is the only taxa for which test methods were developed and standardized on predatory organisms.

Insight into the primary mode of action of TiO2 nanoparticles on Escherichia coli in the dark.

Large-scale production and incorporation of titanium dioxide nanoparticles (NP-TiO2 ) in consumer products leads to their potential release into the environment and raises the question of their toxicity. The bactericidal mechanism of NP-TiO2 under UV light is known to involve oxidative stress due to the generation of reactive oxygen species. In the dark, several studies revealed that NP-TiO2 can exert toxicological effects.

Rapid impact of phenanthrene and arsenic on bacterial community structure and activities in sand batches.

The impact of both organic and inorganic pollution on the structure of soil microbial communities is poorly documented. A short-time batch experiment (6 days) was conducted to study the impact of both types of pollutants on the taxonomic, metabolic and functional diversity of soil bacteria. For this purpose sand spiked with phenanthrene (500 mg kg(-1) sand) or arsenic (arsenite 0.

Improvement of the Caenorhabditis elegans growth and reproduction test to assess the ecotoxicity of soils and complex matrices.

A growth and reproduction test using the nematode Caenorhabditis elegans was recently standardized by the International Organization for Standardization (ISO). Performing the ISO 10872 protocol (2010) revealed some drawbacks when applied to soil or soil mixed with complex matrices. The authors propose some modifications to the current protocol to normalize the test conditions.

Modifications of the bacterial reverse mutation test reveals mutagenicity of TiO(2) nanoparticles and byproducts from a sunscreen TiO(2)-based nanocomposite.

The bacterial reverse mutation test, recommended by the Organization for Economic Co-operation and Development (OECD) to determine genotoxicity of chemical compounds, has been recently used by several authors to investigate nanoparticles. Surprisingly, test results have been negative, whereas in vitro mammalian cell tests often give positive genotoxic responses. In the present study, we used the fluctuation test procedure with the Salmonella typhimurium strains TA97a, TA98, TA100 and TA102 to determine the mutagenic potential of TiO(2) nanoparticles (NP-TiO(2)) and showed that, when it is used conventionally, this test is not suitable for nanoparticle genotoxicity assessment.

Role of electrostatic interactions in the toxicity of titanium dioxide nanoparticles toward Escherichia coli.

The increasing production and use of titanium dioxide nanoparticles (NP-TiO(2)) has led to concerns about their possible impact on the environment. Bacteria play crucial roles in ecosystem processes and may be subject to the toxicity of these nanoparticles. In this study, we showed that at low ionic strength, the cell viability of Escherichia coli was more severely affected at pH 5.

In situ assessment of phytotechnologies for multicontaminated soil management.

Due to human activities, large volumes of soils are contaminated with organic pollutants such as polycyclic aromatic hydrocarbons, and very often by metallic pollutants as well. Multipolluted soils are therefore a key concern for remediation. This work presents a long-term evaluation of the fate and environmental impact of the organic and metallic contaminants of an industrially polluted soil under natural and plant-assisted conditions.

Taxonomic and functional prokaryote diversity in mildly arsenic-contaminated sediments.

Arsenic-resistant prokaryote diversity is far from being exhaustively explored. In this study, the arsenic-adapted prokaryotic community present in a moderately arsenic-contaminated site near Sainte-Marie-aux-Mines (France) was characterized, using metaproteomic and 16S rRNA-encoding gene amplification. High prokaryotic diversity was observed, with a majority of Proteobacteria, Acidobacteria and Bacteroidetes, and a large archaeal community comprising Euryarchaeaota and Thaumarchaeota.

Unsuspected diversity of arsenite-oxidizing bacteria as revealed by widespread distribution of the aoxB gene in prokaryotes.

In this study, new strains were isolated from an environment with elevated arsenic levels, Sainte-Marie-aux-Mines (France), and the diversity of aoxB genes encoding the arsenite oxidase large subunit was investigated. The distribution of bacterial aoxB genes is wider than what was previously thought. AoxB subfamilies characterized by specific signatures were identified.

Arsenic mass balance in a paper mill and impact of the arsenic release from the WWTP effluent on the Moselle River.

Rivers used for drinking water production might be subject to anthropogenic pollution discharge upstream of the intake point. This problem was investigated in the case of the Moselle River, used for water production in Nancy (350,000 inhabitants) and which might be impacted by industrial activities 60 km upstream. The arsenic flux of a pulp and paper mill discharging in the Moselle River at this location has been more specifically investigated.

Characterization of the ars gene cluster from extremely arsenic-resistant Microbacterium sp. strain A33.

The arsenic resistance gene cluster of Microbacterium sp. A33 contains a novel pair of genes (arsTX) encoding a thioredoxin system that are cotranscribed with an unusual arsRC2 fusion gene, ACR3, and arsC1 in an operon divergent from arsC3. The whole ars gene cluster is required to complement an Escherichia coli ars mutant.

Inhibition of transcription in Staphylococcus aureus by a primary sigma factor-binding polypeptide from phage G1.

The primary sigma factor of Staphylococcus aureus, sigma(SA), regulates the transcription of many genes, including several essential genes, in this bacterium via specific recognition of exponential growth phase promoters. In this study, we report the existence of a novel staphylococcal phage G1-derived growth inhibitory polypeptide, referred to as G1ORF67, that interacts with sigma(SA) both in vivo and in vitro and regulates its activity. Delineation of the minimal domain of sigma(SA) that is required for its interaction with G1ORF67 as amino acids 294 to 360 near the carboxy terminus suggests that the G1 phage-encoded anti-sigma factor may occlude the -35 element recognition domain of sigma(SA).

Diversity of arsenite transporter genes from arsenic-resistant soil bacteria.

A PCR approach was developed to assess the occurrence and diversity of arsenite transporters in arsenic-resistant bacteria. For this purpose, three sets of degenerate primers were designed for the specific amplification of approximately 750bp fragments from arsB and two subsets of ACR3 (designated ACR3(1) and ACR3(2)) arsenite carrier gene families. These primers were used to screen a collection of 41 arsenic-resistant strains isolated from two soil samples with contrasting amounts of arsenic.