Search

Nanoplastics (NPs) are omnipresent in the environment and contribute to human exposure. However, little is known regarding the long-term effects of NPs on human health. In this study, human intestinal Caco-2 cells were exposed to polystyrene nanoplastics (nanoPS) in an environmentally relevant concentration range (102–109particles/mL) under two realistic exposure scenarios. In the first scenario, cells were repeatedly exposed to nanoPS every 2 days for 12 days to study the long-term effects. In the second scenario, only nanoPS was added once and Caco-2 cells were cultured for 12 days to study the duration of the initial effects of NPs. Under repeated dosing, initial subtle effects on mitochondria induced by low concentrations would accrue over consistent exposure to nanoPS and finally lead to significant impairment of mitochondrial respiration, mitochondrial mass, and cell differentiation process at the end of prolonged exposure, accompanied by significantly increased glycolysis over the whole exposure period. Single dosing of nanoPS elicited transient effects on mitochondrial and glycolytic functions, as well as increased reactive oxygen species (ROS) production in the early phase of exposure, but the self-recovery capacity of cells mitigated these effects at intermediate culture times. Notably, secondary effects on glycolysis and ROS production were observed during the late culture period, while the cell differentiation process and mitochondrial mass were not affected at the end. These long-term effects are of crucial importance for comprehensively evaluating the health hazards arising from lifetime exposure to NPs, complementing the extensively observed acute effects associated with prevalent short-term exposure to high concentrations. Our study underlines the need to study the toxicity of NPs in realistic long-term exposure scenarios such as repeated dosing.

ABSTRACT The bio-based self-healing concrete market demands an inexpensive bio-agent. The use of axenic ureolytic spore cultures has been demonstrated to be efficient but too expensive, due to an operational [...]

ABSTRACT Bacteria that can induce calcium carbonate precipitation have been studied for self-healing concrete applications. Due to the harsh environment of concrete, i.e. very high pH, small pore size and [...]

The use of advanced membrane processes, such as reverse osmosis (RO) are of great importance for process water and drinking water production. As the water quality is bound to certain imposed microbiological standards, the removal of unwanted bacteria is vital. Reverse osmosis filtration should in theory retain all, or most, bacteria. However, due to operational choices or malfunctions (e.g., leaking glue lines, oxidation of the membrane, loss of O-seals…) bacterial breakthrough can occur. Moreover, certain ultra-small species of bacteria are also able to pass the membrane. Currently, the microbiology and breakthrough are respectively monitored by looking at indicator organisms (e.g., Escherichia coli) viaplating methods and conductivity monitoring. In this case-study on-line flow cytometry was evaluated as a tool to monitor membrane integrity and microbiological quality of a pilot-scale RO membrane system placed at the Citrique Belgium, Citribel site (Tienen, Belgium). Over the course of 20 days, cell density and flow cytometric fingerprinting data were gathered. With the use of these phenotypic fingerprints and conductivity data, we could showcase that the cell densities found in the permeate were due to regrowth within the piping network, rather then bacterial breakthrough of the membrane. This demonstrates the added-value of flow cytometry for microbial and membrane integrity monitoring of large-scale membrane filtration plants.

Photonic integrated circuits (PICs) are expected to add practicality and new functionalities in a considerable number of optical applications, including optical microscopy. Here, we present a PIC design allowing a far-field structured UV illumination pattern with a fringe period as low as $\text{370}\,\text{nm}$, a fringe visibility of 0.83 over field of views of more than $150\,\mu \text{m}\,\times 200\,\mu \text{m}$ and a radiant intensity as large as $\text{0.49}\,\text{mW}$. The circuits include single mode waveguides with propagation losses of $\text{3}\,\text{dB/cm}$ at a wavelength $\lambda =360\,\text{nm}$, two diffraction gratings for beam shaping out of the chip plane, a beam splitter and a phase shifter. Using fluorescent gratings with pitches longer or shorter than the wavelength, as control objects, and a collecting lens with a numerical aperture of 0.5, the current PICs enable to highlight experimentally the Moiré pattern at the heart of the optical resolution enhancement and to achieve a doubling of the optical resolution in the direction of the illumination.

The palladium (Pd)-catalysed reaction has attracted much attention, making Pd the most valuable of the four major precious metals. Several different forms of Pd can be used as a catalyst; nanoparticles (NPs) have the advantage of a high surface area:volume ratio. Since the chemical production of Pd NPs is not environmentally friendly, biological synthesis interest has grown. However, the production mechanism remained unknown in several cases and was recently described for the electroactive bacterium Shewanella oneidensisMR-1. The application of these green synthesised NPs was established in different fields. This review discusses the production pathway and the novel biological-inspired methods to produce tailored biogenic palladium nanoparticles (bio-Pd NPs), with their broad application fields as biogenic nanocatalysts. Two significant applications – reductive bioremediation of persistent organic contaminants and energy-producing microbial fuel cells – are discussed in detail. The current challenges in optimising bio-Pd NPs production and the potential research directions for the complete utilisation of its novel catalytic properties are highlighted.

Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined the variability of interactions between an invader and resident species of its target environment, and none of them considered a bioremediation context. Aminobactersp. MSH1 mineralizing the groundwater micropollutant 2,6-dichlorobenzamide (BAM), is proposed for bioaugmentation of sand filters used in drinking water production to avert BAM contamination. We examined the nature of the interactions between MSH1 and 13 sand filter resident bacteria in dual and triple species assemblies in sand microcosms. The residents affected MSH1-mediated BAM mineralization without always impacting MSH1 cell densities, indicating effects on cell physiology rather than on cell number. Exploitative competition explained most of the effects (70%), but indications of interference competition were also found. Two residents improved BAM mineralization in dual species assemblies, apparently in a mutual cooperation, and overruled negative effects by others in triple species systems. The results suggest that sand filter communities contain species that increase MSH1 fitness. This opens doors for assisting bioaugmentation through co-inoculation with “helper” bacteria originating from and adapted to the target environment.

Currently, biofilms colonizing surfaces are mainly imaged in 2D by conventional techniques, such as optical or scanning electron microscopy. Confocal laser scanning microscopy or optical coherence tomography can visualize biofilms in 3D, but they suffer from a limited penetration depth and cannot visualize biofilms in opaque materials. Micro-computed tomography (µCT) can overcome these issues, but µCT cannot easily distinguish biofilm structures from water due to a lack of contrast difference. Within this research, five contrast-enhancing staining agents (CESAs) were evaluated for their staining potential of cyanobacterial biofilms, aiming to visualize these biofilms in 3D. Isotonic Lugol and 1:2 hafnium(IV)-substituted Wells-Dawson polyoxometalate (Hf-WD 1:2 POM) were the most promising, as they allowed visualization of the biofilms and revealed structures in the stained biofilms. Staining with isotonic Lugol could clearly visualize bundles of filaments within the biofilm, while Hf-WD 1:2 POM revealed a smooth biofilm. It is assumed that both CESAs have a different affinity towards the biofilms and could thus be used complementary. Monolacunary Wells-Dawson polyoxometalate (Mono-WD POM) showed moderate discrimination while staining with cationic iodinated CA4+ and Hexabrix® (Guerbet) containing anionic ioxaglate did not allow to distinctly visualize the biofilms. These results indicate that µCT, together with CESAs such as isotonic Lugol and Hf-WD 1:2 POM, can be used as a tool to image extensive biofilms or microbial mats in 3D. Further research will determine whether these CESAs are suitable for visualizing biofilms within opaque porous media.

Variations in the gut microbiome have been associated with changes in health state such as Crohn’s disease (CD). Most surveys characterize the microbiome through analysis of the 16S rRNA gene. An alternative technology that can be used is flow cytometry. In this report, we reanalyzed a disease cohort that has been characterized by both technologies. Changes in microbial community structure are reflected in both types of data. We demonstrate that cytometric fingerprints can be used as a diagnostic tool in order to classify samples according to CD state. These results highlight the potential of flow cytometry to perform rapid diagnostics of microbiome-associated diseases.

For the production of edible microbial protein (MP), ammonia generated by the Haber-Bosch process or reclaimed ammonia from waste streams is typically considered as the nitrogen source. These processes for ammonia production are highly energy intensive. In this study, the potential for using nitrogen gas (N2) as a direct nitrogen source for MP production by hydrogen-oxidizing bacteria (HOB) was evaluated. The use of N2versus ammonium as nitrogen source during the enrichment process resulted in differentiation of the bacterial community composition of the enrichments. A few previously unknown potential N2-fixing HOB taxa (i.e., representatives of the genus Azonexusand the family Comamonadaceae) dominated the enrichments. The biomass yield of a N2-fixing HOB enrichment was 30–50% lower than that of the ammonium-based HOB enrichment from the same inoculum source. The dried biomass of N2-fixing HOB had a high protein content (62.0 ± 6.3%) and an essential amino acid profile comparable to MP from ammonium-based HOB. MP from N2-fixing HOB could potentially be produced in situ without entailing the emissions caused by ammonia production and transportation by conventional means. It could be a promising substitute for N2-fixing protein-rich soybean because it has 70% higher protein content and double energy conversion efficiency from solar energy to biomass.

Chemical industries around the world show an increasing awareness of their ecological footprint, including their water use. A shift toward alternative water sources, such as wastewater streams or surface water, is slowly becoming a well-known concept to reduce the intake of ground and drinking water. However, a change of intake water often leads to unforeseen challenges (for example, faster breakthrough of organic matter and growth of biofilms) and requires a review of the currently used water treatment technology. A study of surface water used in various Antwerp companies was carried out, but the acquired knowledge can tackle multiple unexpected problems in different applications, as many industries undergo an alteration in their water management due to the increasing water scarcity. Demineralization of Biesbosch surface water by ion exchange and the associated removal of both total organic carbon and microbial cells were investigated with liquid chromatography in combination with organic carbon detection characterization and flow cytometric monitoring. The effect of monochloramine and sodium bisulfite on the ion exchange operation and the respective removal efficiencies were investigated. Considering a total organic carbon limit value of 250 ppb, the addition of both chemicals together had a positive effect on the demineralization operating time. On average, >93% of the organic matter was removed from the incoming feedwater. The organic matter removal mechanism by the anion exchange resins was mostly (acidic) adsorption at low pH in the scavenger and by ion exchange at neutral pH in the weak and strong anion exchange resins. The microbial cell concentration was reduced by almost 2 log units, from 8.16 × 105cells/mL in the feedwater to 8.58 × 103cells/mL in the demineralized water, and was the result of cell lysis due to a large pH drop over the consecutive resin columns. In addition, the end water quality was suited to be used as boiler feedwater, as little to no formation of corrosive organic acids occurred under boiler conditions.

Petroleum hydrocarbons reach the deep-sea following natural and anthropogenic factors. The process by which they enter deep-sea microbial food webs and impact the biogeochemical cycling of carbon and other elements is unclear. Hydrostatic pressure (HP) is a distinctive parameter of the deep sea, although rarely investigated. Whether HP alone affects the assembly and activity of oil-degrading communities remains to be resolved. Here we have demonstrated that hydrocarbon degradation in deep-sea microbial communities is lower at native HP (10 MPa, about 1000 m below sea surface level) than at ambient pressure. In long-term enrichments, increased HP selectively inhibited obligate hydrocarbon-degraders and downregulated the expression of beta-oxidation-related proteins (i.e., the main hydrocarbon-degradation pathway) resulting in low cell growth and CO2production. Short-term experiments with HP-adapted synthetic communities confirmed this data, revealing a HP-dependent accumulation of citrate and dihydroxyacetone. Citrate accumulation suggests rates of aerobic oxidation of fatty acids in the TCA cycle were reduced. Dihydroxyacetone is connected to citrate through glycerol metabolism and glycolysis, both upregulated with increased HP. High degradation rates by obligate hydrocarbon-degraders may thus be unfavourable at increased HP, explaining their selective suppression. Through lab-scale cultivation, the present study is the first to highlight a link between impaired cell metabolism and microbial community assembly in hydrocarbon degradation at high HP. Overall, this data indicate that hydrocarbons fate differs substantially in surface waters as compared to deep-sea environments, with in situ low temperature and limited nutrients availability expected to further prolong hydrocarbons persistence at deep sea.

Water is used for a very broad range of industrial applications with different water quality requirements. In all cases, the microbial water quality remains of importance as the microbial community can cause biofouling, microbial induced corrosion, odor problems, or health hazards. A close and accurate monitoring of the microbial water quality is therefore relevant for all water types used in industrial applications. Flow cytometry and additionally flow cytometric fingerprinting have been proposed before as methods to monitor the aquatic microbial communities but it remains unclear on how sensitive the fingerprinting method is for detecting quality changes in practice for different types of water. In this paper, we compared the microbial dynamics of coarsely filtered surface water, tap water, and demineralized water by challenging these waters with different concentrations and types of nutrients (C, N, and P) and additives such as corrosion inhibitors and biocides. We demonstrated that the cytometric fingerprints of the aquatic microbial communities differed in function of the type and concentration of product added, but that these differences are dependent on the type of water. Flow cytometry proved to be sensitive enough to detect subtle changes in microbial communities and to measure bacterial regrowth in different types of water. As a result, we conclude that cytometric fingerprints can be considered as indirect indicators of the physical–chemical composition of the water and a tool to monitor water biostability, as a tell-tale for minor environmental changes.

A key step toward energy-positive sewage treatment is the development of mainstream partial nitritation/anammox, a nitrogen removal technology where aerobic ammonium-oxidizing bacteria (AerAOB) are desired, while nitrite-oxidizing bacteria (NOB) are not. To suppress NOB, a novel return-sludge treatment was investigated. Single and combined effects of sulfide (0–600 mg S L–1), anaerobic starvation (0–8 days), and a free ammonia (FA) shock (30 mg FA-N L–1for 1 h) were tested for immediate effects and long-term recovery. AerAOB and NOB were inhibited immediately and proportionally by sulfide, with AerAOB better coping with the inhibition, while the short FA shock and anaerobic starvation had minor effects. Combinatory effects inhibited AerAOB and NOB more strongly. A combined treatment of sulfide (150 mg S L–1), 2 days of anaerobic starvation, and FA shock (30 mg FA-N L–1) inhibited AerAOB 14% more strongly compared to sulfide addition alone, while the AerAOB/NOB activity ratio remained constant. Despite no positive change being observed in the immediate-stress response, AerAOB recovered much faster than NOB, with a nitrite accumulation ratio (effluent nitrite on nitrite + nitrate) peak of 50% after 12 days. Studying long-term recovery is therefore crucial for design of an optimal NOB-suppression treatment, while applying combined stressors regularly may lead toward practical implementation.

One of the main challenges for the 21st century is to balance the increasing demand for high-quality proteins while mitigating environmental impacts. In particular, cropland-based production of protein-rich animal feed for livestock rearing results in large-scale agricultural land-expansion, nitrogen pollution, and greenhouse gas emissions. Here we propose and analyze the long-term potential of alternative animal feed supply routes based on industrial production of microbial proteins (MP). Our analysis reveals that by 2050, MP can replace, depending on socio-economic development and MP production pathways, between 10–19% of conventional crop-based animal feed protein demand. As a result, global cropland area, global nitrogen losses from croplands and agricultural greenhouse gas emissions can be decreased by 6% (0–13%), 8% (−3–8%), and 7% (−6–9%), respectively. Interestingly, the technology to industrially produce MP at competitive costs is directly accessible for implementation and has the potential to cause a major structural change in the agro-food system.

Only recently the concept of prebiotics has been introduced in oral health. Few potential oral prebiotics have already been identified in dual species competition assays, showing a stimulatory effect on beneficial bacteria and by this suppressing the outgrowth of pathogenic species. This study aimed to validate the effect of previously identified potential prebiotic substrates on multispecies cultures by shifting the biofilm composition towards a more beneficial species dominated microbiota. A chemostat culture containing 14 model oral bacterial species was used to grow biofilms for 24 hours which subsequently were treated with prebiotic solutions three times a day for 3 consecutive days. Further the influence of environmental factors such as pH, nutrient availability, oxygen concentration and prebiotic dose on the efficacy of the prebiotic substances was investigated. Three potential prebiotic substrates N‐acetyl‐D‐mannosamine, succinic acid and Met‐Pro were able to bring the beneficial proportion to > 95%. While the pH of the prebiotic solution did not have an influence on the prebiotic effect, the interplay of nutrient availability, oxygen concentration and prebiotic treatment resulted in significant changes of the microbial composition identifying N‐acetyl‐D‐mannosamine as the most promising oral prebiotic substrate. Showing a clear dose dependent effect, concentrations of N‐acetyl‐D‐mannosamine of 1.0 and 1.5 M resulted in a biofilm composition of 97% beneficial species. Introducing the prebiotic concept in oral health might reveal a valid approach for treatment and prevention of oral diseases and promote oral health.

Process monitoring of anaerobic digestion is typically based on operational parameters, such as pH and volatile fatty acid concentration, that are lagging on actual microbial community performance. In this study, 13C isotope fractionation in CH4and CO2in the biogas was used to monitor process stability of anaerobic digestion in response to salt stress. A gradual and pulsed increase in salt concentration resulted in a decrease in methane production. No clear shift in δ13CH4was observed in response to the gradual increase in salt concentration, and δ13CO2of the biogas showed only a clear shift after process failure, compared with the control. In contrast, both δ13CH4and δ13CO2in the biogas changed in response to the pulsed increase in salt concentration. This change preceded the decrease in methane production. A significantly different bacterial and archaeal community profile was observed between the DNA and RNA level, which was also reflected in a different relation with the δ13CH4and δ13CO2values. This shows that isotope fractionation in the biogas can predict process stability in anaerobic digestion, as it directly reflects shifts in the total and active microbial community, yet, due to its temporal character, further validation is needed.

High-throughput amplicon sequencing has become a well-established approach for microbial community profiling. Correlating shifts in the relative abundances of bacterial taxa with environmental gradients is the goal of many microbiome surveys. As the abundances generated by this technology are semi-quantitative by definition, the observed dynamics may not accurately reflect those of the actual taxon densities. We combined the sequencing approach (16S rRNA gene) with robust single-cell enumeration technologies (flow cytometry) to quantify the absolute taxon abundances. A detailed longitudinal analysis of the absolute abundances resulted in distinct abundance profiles that were less ambiguous and expressed in units that can be directly compared across studies. We further provide evidence that the enrichment of taxa (increase in relative abundance) does not necessarily relate to the outgrowth of taxa (increase in absolute abundance). Our results highlight that both relative and absolute abundances should be considered for a comprehensive biological interpretation of microbiome surveys.

There is a growing interest in controlling—promoting or avoiding—the invasion of microbial communities by new community members. Resource availability and community structure have been reported as determinants of invasion success. However, most invasion studies do not adhere to a coherent and consistent terminology nor always include rigorous interpretations of the processes behind invasion. Therefore, we suggest that a consistent set of definitions and a rigorous conceptual framework are needed. We define invasion in a microbial community as the establishment of an alien microbial typein a resident communityand argue how simple criteria to define aliens, residents, and alien establishment can be applied for a wide variety of communities. In addition, we suggest an adoption of the community ecology framework advanced by Vellend (2010) to clarify potential determinants of invasion. This framework identifies four fundamental processes that control community dynamics: dispersal, selection, drift and diversification. While selection has received ample attention in microbial community invasion research, the three other processes are often overlooked. Here, we elaborate on the relevance of all four processes and conclude that invasion experiments should be designed to elucidate the role of dispersal, drift and diversification, in order to obtain a complete picture of invasion as a community process.

The increasing production of nitrogen-containing fertilizers is crucial to meet the global food demand, yet high losses of reactive nitrogen associated with the food production/consumption chain progressively deteriorate the natural environment. Currently, mesophilic nitrogen-removing microbes eliminate nitrogen from wastewaters. Although thermophilic nitrifiers have been separately enriched from natural environments, no bioreactors are described that couple these processes for the treatment of nitrogen in hot wastewaters. Samples from composting facilities were used as inoculum for the batch-wise enrichment of thermophilic nitrifiers (350 days). Subsequently, the enrichments were transferred to a bioreactor to obtain a stable, high-rate nitrifying process (560 days). The community contained up to 17% ammonia-oxidizing archaea (AOAs) closely related to ‘CandidatusNitrososphaera gargensis’, and 25% nitrite-oxidizing bacteria (NOBs) related to Nitrospira calida. Incorporation of 13C-derived bicarbonate into the respective characteristic membrane lipids during nitrification supported their activity as autotrophs. Specific activities up to 198±10 and 894±81?mg?N?g-1VSS per day for AOAs and NOBs were measured, where NOBs were 33% more sensitive to free ammonia. The NOBs were extremely sensitive to free nitrous acid, whereas the AOAs could only be inhibited by high nitrite concentrations, independent of the free nitrous acid concentration. The observed difference in product/substrate inhibition could facilitate the development of NOB inhibition strategies to achieve more cost-effective processes such as deammonification. This study describes the enrichment of autotrophic thermophilic nitrifiers from a nutrient-rich environment and the successful operation of a thermophilic nitrifying bioreactor for the first time, facilitating opportunities for thermophilic nitrogen removal biotechnology.

Food is an important dissemination route for antibiotic-resistant bacteria. Factors used during food production and preservation may contribute to the transfer of antibiotic resistance genes, but research on this subject is scarce. In this study, the effect of temperature (7 to 37°C) and modified atmosphere packaging (air, 50% CO2-50% N2, and 100% N2) on antibiotic resistance transfer from Lactobacillus sakeisubsp. sakeito Listeria monocytogeneswas evaluated. Filter mating was performed on nonselective agar plates with high-density inocula. A more realistic setup was created by performing modified atmosphere experiments on cooked ham using high-density and low-density inocula. Plasmid transfer was observed between 10 and 37°C, with plasmid transfer also observed at 7°C during a prolonged incubation period. When high-density inocula were used, transconjugants were detected, both on agar plates and cooked ham, under the three atmospheres (air, 50% CO2-50% N2, and 100% N2) at 7°C. This yielded a median transfer ratio (number of transconjugants/number of recipients) with an order of magnitude of 10-4to 10-6. With low-density inocula, transfer was only detected under the 100% N2atmosphere after 10-day incubation at 7°C, yielding a transfer ratio of 10-5. Under this condition, the highest bacterial density was obtained. The results indicate that low temperature and modified atmosphere packaging, two important hurdles in the food industry, do not necessarily prevent plasmid transfer from Lactobacillus sakeisubsp. sakeito Listeria monocytogenes.

Background:The aim of the current study is to compare the prevalence of commensal bacteria, with beneficial properties, for healthy and diseased individuals and additionally to examine the inhibitory effect of some commercial dietary probiotics on periodontopathogens, comparing this inhibitory effect to that of orally derived beneficial bacteria. Methods:Subgingival plaque samples from 35 patients (healthy and periodontitis patients) were analyzed. Growth inhibition of the periodontal pathogens Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitanswas examined using the agar overlay technique and agar well diffusion method. The quantification of the inhibitory effect was checked with the agar well diffusion method. Results:Using the agar overlay technique, the prevalence of strains antagonistic toward P. gingivalis, A. actinomycetemcomitans,and F. nucleatumwas found to be higher in healthy individuals than in individuals with periodontitis, but this could not be validated by the agar well diffusion assay. Compared with the antagonistic activity of the isolated strains, the probiotic strains overall showed a stronger inhibition of the periodontal pathogens. Conclusion:It was shown that some oral bacteria can cause antagonism toward periodontopathogens, and these observations underline the therapeutic potential of applications that stimulate oral health by the application of beneficial effector strains.

AbstractCurrently, three commercial kits for Bacillus cereusenterotoxins Nhe and/or Hbl detection are available, namely, the Bacillusdiarrheal enterotoxin visual immunoassay (BDE VIA™) kit (3M Tecra), B. cereusenterotoxin reversed passive latex agglutination (BCET-RPLA) kit (Oxoid), and the Duopath®Cereus Enterotoxins (Merck). The performance of the kits and their applicability to gastrointestinal simulation samples were evaluated. Then, the stability and production of enterotoxins Hbl and Nhe under gastrointestinal conditions were investigated. Enterotoxin production was absent or impaired at acidic pH, i.e., in gastric medium with pH 5.0 and lasagne verde with pH 5.5. B. cereusdid produce enterotoxins Nhe and Hbl during anaerobic growth in intestinal medium at pH 7.0, but the toxins were instantly degraded by the enzymes in the host's digestive secretions. Preformed enterotoxins did not withstand gastrointestinal passage under the simulated conditions, which suggests that preformed enterotoxins in food do not contribute to the diarrheal food poisoning syndrome. In conclusion, diarrhea is probably caused by de novoenterotoxin production by B. cereuscells located closely to the host's intestinal epithelium.

The enteric pathogen Bacillus cereusmust survive gastric passage in order to cause diarrhea by enterotoxin production in the small intestine. The acid resistance and the survival after gastric passage were assessed by in vitro experiments with acidified growth medium and gastric simulation medium with B. cereusNVH 1230-88 vegetative cells and spores. First, batch incubations at constant pH values for 4 h, which represented different physiological states of the stomach, showed that spores were resistant to any gastric condition in the pH range of 2.0 to 5.0, while vegetative cells were rapidly inactivated at pH values of ≤4.0. Second, a dynamic in vitro gastric experiment was conducted that simulated the continuously changing in vivo conditions due to digestion dynamics by gradually decreasing the pH from 5.0 to 2.0 and fractional emptying of the stomach 30 to 180 min from the start of the experiment. All of the B. cereusspores and 14% (± 9%) of the vegetative cells survived the dynamic simulation of gastric passage.

Abstract: The interaction between Shewanella oneidensis MR-1 and the soluble metal Pd(II) during the reductive precipitation of Pd(0) determined the size and properties of the precipitated Pd(0) nanoparticles. Assessment of cell viability indicated that the bioreduction of Pd(II) was a detoxification mechanism depending on the Pd(II) concentration and on the presence and properties of the electron donor. The addition of H2 in the headspace allowed S. oneidensis to resist the toxic effects of Pd(II). Interestingly, 25 mM formate was a less effective electron donor for bioreductive detoxification of Pd(II), since there was a 2 log reduction of culturable cells and a 20% decrease of viable cells within 60 min, followed by a slow recovery. When the ratio of Pd:cell dry weight (CDW) was below 5:2 at a concentration of 50 mg l−1 Pd(II), most of the cells remained viable. These viable cells precipitated Pd(0) crystals over a relatively larger bacterial surface area and had a particle area that was up to 100 times smaller when compared to Pd(0) crystals formed on non-viable biomass (Pd:CDW ratio of 5:2). The relatively large and densely covering Pd(0) crystals on non-viable biomass exhibited high catalytic reactivity towards hydrophobic molecules such as polychlorinated biphenyls, while the smaller and more dispersed nanocrystals on a viable bacterial carrier exhibited high catalytic reactivity towards the reductive degradation of the anionic pollutant perchlorate.

A Chlamydophila psittaci species-specific real-time PCR targeting the rDNA ribosomal spacer was developed as well as a genotype-specific real-time PCR targeting the Cp. psittaci outer membrane protein A (ompA) gene. The SYBR Green-based species-specific real-time PCR detected Cp. psittaci genotypes A to F, and the recently discovered E/B genotype. The genotype-specific real-time PCR could easily distinguish genotypes C, D, F by use of TaqMan probes. Genotypes A, B and E could not be distinguished from each other by simply using TaqMan probes. For this purpose, non-fluorescent competitor oligonucleotides, had to be used next to the TaqMan probes. Genotype E/B could only be detected by use of a minor groove binder (MGB) probe. Both real-time PCR assays allowed reproducible, sensitive (10 rDNA or ompA copies/$\mu$L DNA extract) and specific detection of Cp. psittaci DNA. The genotype-specific real-time PCR was compared to ompA sequencing and ompA restriction fragment length polymorphism (RFLP) analysis using five Cp. psittaci field isolates (99, 61/8, 7344/2, 8615/1 and 7778B15) each consisting of two different genotypes. The currently developed real-time PCR assays were used in a case study on a veterinary school and a turkey farm. In the veterinary school, Cp. psittaci genotypes D, E/B and F infection were detected in all five groups of turkeys, and one veterinarian who was taking care of all these turkeys. On the turkey farm, the presence of two Cp. psittaci genotype B infection waves was demonstrated in one randomly selected turkey, the first wave at the age of 6 weeks, and the second at the age of 12 weeks.

Innovative and sustainable technologies are being developed to meet the demand for critical and economically important metals and to minimize and valorize the increasing quantities of industrial waste streams. This study investigates a valorization route for the recovery of copper from a copper sulfide tailing (0.4 wt % Cu). Microwave-assisted roasting was used to transform the sulfidic fraction into a sulfate fraction, which increased the solubility of copper and other heavy metals during the following leaching steps. The roasted material was leached with an ammonia solution, and the effect on the leaching efficiency of varying the ammonia concentration was investigated. Simultaneous ammoniacal leaching and solvent extraction resulted in a high leaching efficiency of copper (nearly 100%) with a high selectivity against iron (less than 1% leaching efficiency). An indirect bioleaching step with biogenic citric acid, supported by a comparative leaching using purified organic acids, was applied to further decrease the concentration of residual metals (i.e., more than 40% leaching efficiency for Mn, around 20% leaching efficiency for Zn, and 5% leaching efficiency for Cu) and simultaneously neutralizing the pH of the substrate. A standardized environmental leaching test was performed on every leaching residue to evaluate the performance of the process.