Engineered nanomaterials (ENMs) are specifically designed with different functionalities to satisfy required industrial, medical or commercial purposes. The inevitable release of these materials to the environment may impact negatively bacteria that are essential for the ecosystem’s well-being. This work aimed to identify features that determine the hazardous nature of nanomaterials to bacteria. At first, the bacterial growth inhibition concentrations for silver (Ag), cupric oxide (CuO), cadmium telluride quantum dots (CdTe QDs), titanium dioxide (TiO2), nanodiamonds and multi-walled carbon nanotubes were determined on Escherichia coli K-12 MG1655 grown in 96-well plates. The nano-forms of Ag, CuO, TiO2 and the CdTe QDs were found to display more growth inhibitory effects than their bulk equivalents. The metal salts of silver and copper were still more toxic than their equivalent ENM forms; on the contrary the CdTe QDs were found to be more toxic than their metal salts equivalent. The surface coatings of the ENMs were not found to be significant contributors of bacterial growth inhibition. This screening assay could be adapted as a first tier approach; providing an early input into the hazard assessment of nanomaterials to bacteria. The upscale determination of bacterial growth inhibition tests in 250 ml Erlenmeyer flasks manifested similar results to those observed in 96-well plates. The growth inhibition tests with E. coli were also conducted in an anaerobic fermentative environment. The presence of the ENMs was not found to disrupt the functionality of the fermentation respiratory pathway of the bacterium. However, the results indicated a more severe bacterial growth inhibition response to the presence of silver, copper and the cadmium/tellurium based ENMs as compared to the aerobic growth exposures. Finally, from the adaptation of a human ingestion simulation of soil containing CuO NPs, no greater concerns of metal bioaccessibility were identified from the potential ingestion of the nano-forms of CuO versus the metal salt.

Per- and polyfluorinated alkyl substances (PFASs) belong to a large group of man-made chemicals that pollute the environment. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most commonly found PFASs. The pollution of PFASs can be caused among others by using of aqueous fire-fighting foams (AFFFs). PFASs are persistent compounds; that can travel long distances and bioaccumulate in biota. There are several exposure routes for PFASs, but the most common are via food and drinking water. A possible way for PFASs to enter the food chain is by adsorption to microbes. In this project, binding of PFASs to three gram-negative bacteria, Eschericha coli, Acidovorax delafieldii and Pseudomonas nitroreducens, was assessed. Microbes were exposed for fluorinated compounds in environmental water samples and a PFAS-11 solution with 11 PFAS substances prepared in the laboratory. The binding seems to be preferential to the most abundant compounds, PFOS, since the second most abundant compound in the samples was PFHxS with concentrations at one third of the PFOS concentration but nonetheless PFHxS was not detected in any of the samples. The binding of mainly one PFAS was identified; PFOS was bound at highest concentrations in E. coli treated with both environmental water sample and a PFAS-11 solution. Low concentrations of FOSA and PFDoDS were identified in E. coli and PFNA in A. delafieldii. Only PFOS was detected in P. nitroreducens. The concentrations of other PFASs were below their respective method detection limits.

Aeolian dust exerts a notable influence on atmospheric and oceanic conditions and human health, particularly in arid and semi-arid regions like Saudi Arabia. Dust is often characterized by its mineral and chemical composition, but there is a microbiological component of natural aerosols which has received comparatively little attention. Moreover, the amount of materials suspended in the atmosphere is highly variable from day to day. Thus, knowing the loads of dust and suspended microbes and its variability over the year is essential to understand the possible effects of dust on the Red Sea ecosystem. Here, we present the first estimates of dust and microbial loads at a coastal side on the Red Sea over a two-year period supplemented with information from dust samples collected along the Red Sea in offshore water and their variability. Weekly average dust loads ranged from 4.63 to 646.11 μg m-3, while the abundance of airborne prokaryotic cells and viral particles ranged from 31,457 to 608,333 cells m-3 and from 69,615.5 to 3,104,758 particles m-3, respectively. These are the first estimates of airborne microbial abundance that we are aware of in this region. The large number of dust particles and suspended microbes found in the air indicates that airborne microbes may have a large impact on our health and that of the Red Sea ecosystem.

Les maladies allergiques ont fortement augmenté dans les pays industrialisés depuis les années qui ont suivi la 1ère guerre mondiale. Parmi les hypothèses proposées celle de l’implémentation de l’hygiène dans l’environnement urbain et ses conséquences sur l’exposition aux agents pathogènes a été bien documentée. Comparé à la vie rurale, l’environnement urbain entraine une exposition plus faible aux microbes et à leurs constituants moléculaires tels que les endotoxines et quasi nulle aux parasites intestinaux tels que les helminthes. Au contraire, l’exposition aux allergènes de l’environnement domestique est plus importante.Dans ce travail nous avons investigué certains aspects de la réponse inflammatoire induite par les endotoxines (une molécule pro-inflammatoires des bactéries Gram négatives) et immunitaire associée aux helminthes.1/ L'exposition chronique à l'endotoxine inhalée produit des effets paradoxaux :une protection contre le développement d'allergies IgE-médiées, d'une part, et une réaction inflammatoire des voies aériennes, d'autre part. Comme les régions de la déposition bronchique et alvéolaire pourraient jouer un rôle dans ce processus, nous avons évalué la réponse inflammatoire locale et systémique après exposition à de l'endotoxine par inhalation d'aérosols de particules de dimensions différentes. Les résultats montrent une relation entre la déposition au niveau pulmonaire et l’amplitude de la réponse inflammatoire systémique.2/ Les infections parasitaires ont une relation complexe avec les maladies allergiques. Ces deux pathologies se caractérisent par une réponse immunitaire de type Th2 (impliquant éosinophiles, immunoglobulines E (IgE), interleukine (IL)-4, IL-13,IL-5, …). Cependant, certaines helminthiases protègent des maladies allergiques. Dans cette seconde partie du travail, nous avons étudié la réponse immune induite par une infection chronique par ankylostomes chez l’humain et son évolution après traitement de l’infection. Nous confirmons que la réponse immune au cours de l’infection à ankylostome est caractérisée par une augmentation des cellules T régulatrices (Treg), qui contrôlent l’amplitude de la réponse immune aux helminthes mais montrons pour la première fois que ces Treg ont un phénotype naïf et fortement immuno-suppresseur. Deux semaines après traitement de l’infection on observait également une réponse inflammatoire caractérisée par une majoration de l’IL-6 mais aussi de l’IL-4, cytokine Th2 qui joue un rôle majeur dans la production d’IgE. Ces réponses conjointes (diminution des Treg et réponse inflammatoire de type Th2) pourraient constituer une base physiopathologique pouvant expliquer l’augmentation de la prévalence des sensibilisations allergiques après traitement d’une helminthiase. Nous montrons également que l’infection par helminthes s’accompagne d’une production d’IgE reconnaissant de nombreux allergènes dont les acariens de la poussière de maison, un des allergènes respiratoires les plus fréquents et fortement inducteur d’asthme. Le mécanisme expliquant la production de ces IgE spécifiques des acariens n’est pas connu. Il pourrait s’agir d’une production polyclonale, par présentation facilitée par les IgE ou par réactivité croisée avec des antigènes parasitaires. Ces IgE n’induisaient ni sensibilisation cutanée (tests allergiques cutanés positifs), ni symptomatologie clinique et n’étaient pas capables d’induire de dégranulation des mastocytes in vitro après stimulation allergénique. Par ailleurs, ces IgE spécifiques ne reconnaissaient ni les allergènes majeurs ni des déterminants carbohydrates de type N-glycan.En conclusion, notre travail de thèse met en lumière des mécanismes potentiels par lesquels l’exposition aux agents microbiens environnementaux peut moduler les réponses immunes et protègent potentiellement des maladies allergiques. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished

Water samples were taken at the KAUST RO plant, the WDRC pilot plant and three other full-scale desalination installations in Saudi Arabia. The water was characterized using selected microbiological parameters, being conventional (heterotopic place count (HPC), total coliforms, Escherichia coli) and more novel and sensitive methods (adenosine tri-phosphate (ATP, a measure for bacterial activity), as well as total and intact bacterial cell concentrations (TDC using flow cytometry) and supporting parameters (pH, conductivity, residual chlorine and temperature). Selective samples were used to quantify the bacterial growth potential (“food for the bacteria”), applying a flow cytometer based easily Assimilable Organic Carbon (AOC) assay. Hypothesized was that no or very low bacterial numbers would occur after RO filtration in the plants due to the high rejection properties of the RO membranes and the produced water exceptionally low mineral and nutrient content. Key findings are that the (i) RO permeate contains bacterial cell concentrations exceeding 1.0 × 103 cells/mL. The highest percentage of cells are intact and active, based on the ATP and total cell counts (ii) advanced microbial parameters ATP and TDC enabled to detect and quantify bacteria numbers and activity while the less sensitive conventional plate counts based techniques did not, (iii) flow cytometer-based growth potential measurements indicate the presence of 8 µg AOC/L in the RO permeate. A typical last step in drinking water production is chlorination, effectively inactivating all the bacterial cells. The origin of the bacterial cells and the biodegradable nutrients enabling the bacterial growth in the RO permeate is not clear. There is a clear need to assess the origin of the nutrients and bacteria found in the RO produced water. It is not expected to be passing the RO membrane.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / The Succulent Karoo Biome (SKB) in South Africa is widely reputed to house Earth’s greatest diversity of succulent plants. It is also famous for spectacular displays of annual flowers after good rains. The area experiences winter rainfall which infrequently exceeds 100 mm per annum but certain parts of the SKB can get 250 mm. Irrigated agriculture on a large scale was therefore not a viable option when European farmers began colonizing the land. The land was conquered from the indigenous Khoekhoe herders and San hunter-gatherers, South Africa’s first peoples. The biome underwent extreme transformation in the last 200 years following colonisation which resulted in homogenization of the landscape and extinction of many succulents thus reducing biodiversity.

Yes / Introduction: Mobile phones are used the world over, including in healthcare settings. This study aimed to investigate the viable microbial colonisation of mobile phones used by healthcare personnel. Methods: Swabs collected on the same day from 30 mobile phones belonging to healthcare workers from three separate paediatric wards of an Australian hospital were cultured on five types of agar plate, then colonies from each phone were pooled, extracted and sequenced by shotgun metagenomics. Questionnaires completed by staff whose phones were sampled assisted in the analysis and interpretation of results. Results and discussion: All phones sampled cultured viable bacteria. Overall, 399 bacterial operational taxonomic units were identified from 30 phones, with 1432 cumulative hits. Among these were 58 recognised human pathogenic and commensal bacteria (37 Gram-negative, 21 Gram-positive). The total number of virulence factor genes detected was 347, with 1258 cumulative hits. Antibiotic resistance genes (ARGs) were detected on all sampled phones and overall, 133 ARGs were detected with 520 cumulative hits. The most important classes of ARGs detected encoded resistance to beta-lactam, aminoglycoside and macrolide antibiotics and efflux pump mediated resistance mechanisms. Conclusion: Mobile phones carry viable bacterial pathogens and may act as fomites by contaminating the hands of their users and indirectly providing a transmission pathway for hospital-acquired infections and dissemination of antibiotic resistance. Further research is needed, but meanwhile adding touching mobile phones to the five moments of hand hygiene is a simple infection control strategy worth considering in hospital and community settings. Additionally, the implementation of practical and effective guidelines to decontaminate mobile phone devices would likely be beneficial to the hospital population and community at large.

Yes / The mechanisms regulating community composition and local dominance of trees in species-rich forests are poorly resolved, but the importance of interactions with soil microbes is increasingly acknowledged. Here, we show that tree seedlings that interact via root-associated fungal hyphae with soils beneath neighbouring adult trees grow faster and have greater survival than seedlings that are isolated from external fungal mycelia, but these effects are observed for species possessing ectomycorrhizas (ECM) and not arbuscular mycorrhizal (AM) fungi. Moreover, survival of naturally-regenerating AM seedlings over ten years is negatively related to the density of surrounding conspecific plants, while survival of ECM tree seedlings displays positive density dependence over this interval, and AM seedling roots contain greater abundance of pathogenic fungi than roots of ECM seedlings. Our findings show that neighbourhood interactions mediated by beneficial and pathogenic soil fungi regulate plant demography and community structure in hyperdiverse forests. / This research was funded by the National Key Research and Development Program of China (Project No. 2017YFA0605100) and the National Natural Science Foundation of China (NSFC 31770466 to X.L. and 31870403 to M.L.), and partly supported by awards from the UK Natural Environment Research Council (NERC NE/M004848/1 and NE/R004986/1). D.J. is also supported by the N8 AgriFood programme.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24184号 / 理博第4875号 / 新制||理||1698(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 半谷 吾郎, 准教授 Huffman Michael Alan, 教授 今井 啓雄 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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