Antimicrobial efficacy and amino acid substitutions associated with susceptibility to the tellurium compound AS101 against Haemophilus influenzae and Haemophilus parainfluenzae.

The tellurite toxicity in Haemophilus influenzae and H. parainfluenzae remains unclear. To understand the potential of tellurite as a therapeutic option for these bacteria, we investigated the antimicrobial efficacy of AS101, a tellurium compound, against H. influenzae and H. parainfluenzae and the molecular basis of their differences in AS101 susceptibility. Through broth microdilution, we examined the minimum inhibitory concentration (MIC) of AS101 in 51 H. influenzae and 28 H. parainfluenzae isolates. Whole-genome sequencing was performed on the H. influenzae isolates to identify genetic variations associated with AS101 susceptibility. The MICs of AS101 were ≦ 4, 16-32, and ≧ 64 µg/mL in 9 (17.6%), 12 (23.5%), and 30 (58.8%) H. influenzae isolates, respectively, whereas ≦ 0.5 µg/mL in all H. parainfluenzae isolates, including multidrug-resistant isolates. Time-killing kinetic assay and scanning electron microscopy revealed the in vitro bactericidal activity of AS101 against H. parainfluenzae. Forty variations in nine tellurite resistance-related genes were associated with AS101 susceptibility. Logistic regression, receiver operator characteristic curve analysis, Venn diagram, and protein sequence alignment indicated that Val195Ile substitution in TerC, Ser93Gly in Gor (glutathione reductase), Pro44Ala/Ala50Pro in NapB (nitrate reductase), Val307Leu in TehA (tellurite resistance protein), Cys105Arg in CysK (cysteine synthase), and Thr364Ser in Csd (Cysteine desulfurase) were strongly associated with reduced AS101 susceptibility, whereas Ser155Pro in TehA with increased AS101 susceptibility. In conclusions, the antimicrobial efficacy of AS101 is high against H. parainfluenzae but low against H. influenzae. Genetic variations and corresponding protein changes relevant to AS101 non-susceptibility in H. influenzae were identified.

Biosynthesis of uniform fluorescent-stable telluride quantum dots in Escherichia coli and its detection of Fe3+ in water.

Quantum dots (QDs) containing zinc (Zn) and tellurium (Te) have low toxicity and excellent optoelectronic properties, which make them ideal fluorescent probes for use in environmental monitoring. However, their size/shape distribution synthesized by existing methods is not as good as that of other nanoparticles, thus limiting their application. Exploring whether this kind of QD can be biosynthesized and whether it can act as a nanoprobe are favorable attempts to expand the synthesis method and the application of QDs. Telluride QDs were biosynthesized in Escherichia coli cells. The nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and inductively coupled plasma-atomic emission spectrometry (ICP‒AES), indicating that they were Zn3STe2 QDs. The QDs were monodispersed, spherical and fluorescently stable, with a uniform particle size of 3.05 ± 0.48 nm. The biosynthesis conditions of the QDs, including substrate concentrations and their process time, were optimized respectively. It was verified that the cysE and cysK genes were involved in the biosynthesis of telluride QDs. The biosynthesis ability of the QDs was improved by knocking out the tehB gene and overexpressing the pckA gene. Escherichia coli BW25113 cells that synthesized Zn3STe2 QDs were used as environmentally friendly fluorescent bioprobes to specifically select and quantitatively detect Fe3+ in water with a low limit of detection (2.62 µM). The fluorescent cells were also photobleach resistant and had good fluorescence stability. This study expands on the synthesis method of telluride QDs and the application of fluorescent probes.

Gordonia metallireducens sp. nov., a tellurite- and selenite-resistant bacterium isolated from the sediment of an acid mine drainage stream.

A polyphasic taxonomic study was carried out on strain TSed Te1T, isolated from sediment of a stream contaminated with acid drainage from a coal mine. The bacterium forms pink-pigmented colonies and has a rod-coccus growth cycle, which also includes some coryneform arrangements. This bacterium is capable of growing in the presence of up to 750 µg ml-1 tellurite and 5000 µg ml-1 selenite, reducing each to elemental form. Nearly complete 16S rRNA gene sequence analysis associated the strain with Gordonia, with 99.5 and 99.3 % similarity to Gordonia namibiensis and Gordonia rubripertincta, respectively. Computation of the average nucleotide identity and digital DNA-DNA hybridization comparisons with the closest phylogenetic neighbour of TSed Te1T revealed genetic differences at the species level, which were further substantiated by differences in several physiological characteristics. The dominant fatty acids were C16 : 0, C18 : 1, C16 : 1 and tuberculostearic acid. The DNA G+C content was 67.6 mol%. Major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside, while MK-9(H2) was the only menaquinone found. Mycolic acids of C56-C60 were present. Whole-cell hydrolysates contained meso-diaminopimelic acid along with arabinose and galactose as the major cell-wall sugars. On the basis of the results obtained in this study, the bacterium was assigned to the genus Gordonia and represents a new species with the name Gordonia metallireducens sp. nov. The type strain is TSed Te1T (=NRRL B-65678T=DSM 114093T).

Evaluating the incidence of ampC-ß-lactamase genes, biofilm formation, and antibiotic resistance among hypervirulent and classical Klebsiella pneumoniae strains.

AIM: Both immunocompetent and healthy individuals can become life-threateningly ill when exposed to the hypervirulent (hvKp) strains of Klebsiella pneumoniae (Kp). The main objectives of this study were to evaluate the presence of ampC-lactamase genes, biofilm formation, and antibiotic resistance in clinical strains of hvKp and cKp (classical K. pneumoniae). MATERIALS AND METHODS: Kp strains were collected from patients referred to Shahidzadeh Hospital in Behbahan City, Khuzestan Province, Iran. Several techniques were used to identify hvKp. The hypermucoviscosity phenotype was determined using the string test. Isolates that developed dark colonies on tellurite agar were assumed to be hvKp strains. If any of the iucA, iutA, or peg-344 genes were detected, the isolates were classified as hvKp. Phenotypic and genotypic detection of AmpC ß-lactamases of hvKp strains was performed by the combined disk method and polymerase chain reaction, respectively. In addition, crystal violet staining was used to determine the biofilm formation of these isolates. RESULTS: For this study, 76 non-duplicative isolates of Kp were collected. Overall, 22 (28.94%) strains had positive string test results, and 31 (40.78%) isolates were grown in tellurite-containing medium. The genes iucA and iutA or peg-344 were found in 23.68% of all Kp strains and in 50% of tellurite-resistant isolates, respectively. The most effective antibiotics against hvKp isolates were tetracycline (85.52%) and chloramphenicol (63.15%). Using the cefoxitin disc diffusion method, we observed that 56.57% (43/76) of the strains were AmpC producer. A total of 30.26% (n = 23/76) of the isolates tested positive for at least one ampC gene, including blaDHA (52.63%, n = 40), blaCIT (40.78%, n = 31), blaACC (19.76%, n = 15), blaMOX (25%, n = 19), and blaFOX (43.42%, n = 33). Biofilm formation analysis revealed that most hvKp isolates were weak (n = 6, 40%) and moderate (n = 5, 33.33%) biofilm producers. CONCLUSION: Healthcare practitioners should consider the possibility of the existence and acquisition of hvKp everywhere. The exact mechanisms of bacterial acquisition are also unknown, and it is unclear whether the occurrence of infections is related to healthcare or not. Thus, there are still many questions about hvKp that need to be investigated.

The cryptic step in the biogeochemical tellurium (Te) cycle: Indirect elementary Te oxidation mediated by manganese-oxidizing bacteria Bacillus sp. FF-1.

Tellurium (Te) is a rare element within the chalcogen group, and its biogeochemical cycle has been studied extensively. Tellurite (Te(IV)) is the most soluble Te species and is highly toxic to organisms. Chemical or biological Te(IV) reduction to elemental tellurium (Te0) is generally considered an effective detoxification route for Te(IV)-containing wastewater. This study unveils a previously unnoticed Te0 oxidation process mediated by the manganese-oxidizing bacterium Bacillus sp. FF-1. This bacterium, which exhibits both Mn(II)-oxidizing and Te(IV)-reducing abilities, can produce manganese oxides (BioMnOx) and Te0 (BioTe0) when exposed to Mn(II) and Te(IV), respectively. When 5 mM Mn(II) was added after incubating 0.1 mM or 1 mM Te(IV) with strain FF-1 for 16 h, BioTe0 was certainly re-oxidized to Te(IV) by BioMnOx. Chemogenic and exogenous biogenic Te0 can also be oxidized by BioMnOx, although at different rates. This study highlights a new transformation process of tellurium species mediated by manganese-oxidizing bacteria, revealing that the environmental fate and ecological risks of Te0 need to be re-evaluated.

Thermal, structural, optical, and photon shielding studies of cerium-doped barium tellurite glasses.

A series of tellurite-based glasses are prepared by using a melt-quenching method. The effect of cerium on the physical, thermal, structural, optical, spectroscopic, and shielding properties of barium tellurite glass samples is studied. It has been observed that the thermal stability factor increases with increasing cerium ion (Ce3+ ) concentration. The density and other physical parameters such as ion concentration and molar volume are calculated using the Archimedes principle. An increase in optical band gap and density suggests a decrement in non-bridging oxygens. These results are in accordance with Raman results. The blue emission in prepared glasses is studied in terms of International Commission on Illumination chromaticity coordinates. Moreover, various shielding properties such as mass attenuation coefficient, linear attenuation coefficient, effective atomic number, half-value layer, and tenth-value layer have also been determined to understand the photon shielding characteristics of as-prepared glass samples.

Comprehensive Numerical Analysis of Temperature Sensitivity of Spherical Microresonators Based on Silica and Soft Glasses.

In recent years, the use of optical methods for temperature measurements has been attracting increased attention. High-performance miniature sensors can be based on glass microspheres with whispering gallery modes (WGMs), as their resonant frequencies shift in response to the ambient parameter variations. In this work, we present a systematic comprehensive numerical analysis of temperature microsensors with a realistic design based on standard silica fibers, as well as commercially available special soft glass fibers (GeO2, tellurite, As2S3, and As2Se3). Possible experimental implementation and some practical recommendations are discussed in detail. We developed a realistic numerical model that takes into account the spectral and temperature dependence of basic glass characteristics in a wide parameter range. To the best of our knowledge, spherical temperature microsensors based on the majority of the considered glass fibers have been investigated for the first time. The highest sensitivity dλ/dT was obtained for the chalcogenide As2Se3 and As2S3 microspheres: for measurements at room temperature conditions at a wavelength of λ = 1.55 µm, it was as high as 57 pm/K and 36 pm/K, correspondingly, which is several times larger than for common silica glass (9.4 pm/K). Importantly, dλ/dT was almost independent of microresonator size, WGM polarization and structure; this is a practically crucial feature showing the robustness of the sensing devices of the proposed design.

Tellurite Glasses from the 70TeO2-5XO-10P2O5-10ZnO-5PbF2(X= Pb, Bi, Ti) System Doped Erbium Ions-The Influence of Erbium on the Structure and Physical Properties.

In this article, we present research on the influence of erbium ions on the structure and magneto-optical properties of 70TeO2-5XO-10P2O5-10ZnO-5PbF2 (X = Pb, Bi, Ti) tellurite glass systems. Structural changes occurring in the glasses during doping with erbium ions were investigated using positron annihilation lifetime spectroscopy (PALS) and Raman spectroscopy. The X-ray diffraction (XRD) method was used to confirm the amorphous structure of the investigated samples. Based on the Faraday effect measurements and calculated values of Verdet constant, the magneto-optical properties of the glasses were determined.

Anaerobic RSH-dependent tellurite reduction contributes to Escherichia coli tolerance against tellurite.

BACKGROUND: Tellurium is a rare metalloid that exerts high toxicity on cells, especially on bacteria, partly due to reactive oxygen species (ROS) generation. Moreover, it has also been observed that tellurite can target free cell thiols groups (RSH) (i.e. reduced glutathione (GSH)), enhancing the cellular redox imbalance. Additionally, in vitro experiments have suggested that several enzymes can reduce tellurite (IV) to its elemental form (0); where RSH present on their active sites may be responsible for the process. Nevertheless, the mechanisms implemented by bacteria for tellurite reduction and its role in resistance have not been evaluated in vivo. RESULTS: This work shows that tellurite reduction to elemental tellurium is increased under anaerobic conditions in E. coli cells. The in vivo tellurite reduction is related to the intracellular concentration of total RSH, in the presence and absence of oxygen. This metabolization of tellurite directly contributes to the resistance of the bacteria to the oxyanion. CONCLUSIONS: We demonstrated that in vivo tellurite reduction is related to the intracellular thiol concentration, i.e. large availability of cellular RSH groups, results in a more significant reduction of tellurite. Furthermore, we observed that, when the bacterium exhibits less resistance to the oxyanion, a decreased tellurite reduction was seen, affecting the growth fitness. Together, these results let us propose that tellurite reduction and the intracellular RSH content are related to the oxyanion bacterial resistance, this tripartite mechanism in an oxygen-independent anaerobic process.

Tellurite and Selenite: how can these two oxyanions be chemically different yet so similar in the way they are transformed to their metal forms by bacteria?

This opinion review explores the microbiology of tellurite, TeO32- and selenite, SeO32- oxyanions, two similar Group 16 chalcogen elements, but with slightly different physicochemical properties that lead to intriguing biological differences. Selenium, Se, is a required trace element compared to tellurium, Te, which is not. Here, the challenges around understanding the uptake transport mechanisms of these anions, as reflected in the model organisms used by different groups, are described. This leads to a discussion around how these oxyanions are subsequently reduced to nanomaterials, which mechanistically, has controversies between ideas around the molecule chemistry, chemical reactions involving reduced glutathione and reactive oxygen species (ROS) production along with the bioenergetics at the membrane versus the cytoplasm. Of particular interest is the linkage of glutathione and thioredoxin chemistry from the cytoplasm through the membrane electron transport chain (ETC) system/quinones to the periplasm. Throughout the opinion review we identify open and unanswered questions about the microbial physiology under selenite and tellurite exposure. Thus, demonstrating how far we have come, yet the exciting research directions that are still possible. The review is written in a conversational manner from three long-term researchers in the field, through which to play homage to the late Professor Claudio Vásquez.

The Development and Evaluation of a Selective Enrichment for the Detection of Escherichia albertii in Food.

Escherichia albertii is an emerging pathogen causing foodborne infections with diarrhea, abdominal pain, and fever. E. albertii has been isolated from various food sources, such as chicken and pork. Although many foodborne outbreaks of E. albertii have been reported, the causative food has not been identified. It is necessary to develop effective detection methods for E. albertii. Because enrichment procedure as the first step of food test is important for growing pathogens, this study aimed to develop a novel effective enrichment for E. albertii detection in food. In this study, we investigated the optimal concentration and combination of cefixime and tellurite for supplementing modified EC broth (mEC) to effectively isolate E. albertii from chicken meat. The results showed that mEC supplemented with 50 µg/L cefixime and 2.5 mg/L tellurite (CT-mEC) inhibited the growth of competitive bacteria in chicken meat but not that of E. albertii. Therefore, it was indicated that CT-mEC had strong potential to selectively grow E. albertii. In an E. albertii foodborne outbreak, CT-mEC was evaluated. E. albertii was successfully isolated from a food sample, a kind of salad, by enrichment with CT-mEC but not buffered peptone water and mEC. In this study, CT-mEC as a selective enrichment broth has been developed to detect E. albertii in chicken meat. It was demonstrated that the selective enrichment broth was effective for the efficient detection of E. albertii in food.

Cascade Brillouin Lasing in a Tellurite-Glass Microsphere Resonator with Whispering Gallery Modes.

Brillouin microlasers based on microresonators with whispering gallery modes (WGMs) are in high demand for different applications including sensing and biosensing. We fabricated a microsphere resonator with WGMs from a synthesized high-quality tellurite glass with record high Q-factors for tellurite microresonators (Q ≥ 2.5 × 107), a high Brillouin gain coefficient (compared to standard materials, e.g., silica glasses), and a Brillouin frequency shift of 9 ± 0.5 GHz. The high density of excited resonance modes and high loaded Q-factors allowed us to achieve experimentally cascade Stokes-Brillouin lasing up to the 4th order inclusive. The experimental results are supported by the results of the theoretical analysis. We also theoretically obtained the dependences of the output Brillouin powers on the pump power and found the pump-power thresholds for the first five Brillouin orders at different values of pump frequency detuning and Q-factors, and showed a significant effect of these parameters on the processes under consideration.

Investigation into the Antibacterial Mechanism of Biogenic Tellurium Nanoparticles and Precursor Tellurite.

Antibacterial tellurium nanoparticles have the advantages of high activity and biocompatibility. Microbial synthesis of Te nanoparticles is not only a green technology but builds new ecological relationships in diverse environments. However, the antibacterial mechanism of Te nanoparticles is largely unclear. In this study, we report the bacterial synthesis of rod-shaped Te nanoparticles (BioTe) with high antibacterial activity against Escherichia coli. Morphology and permeability examination indicates that membrane damage is the primary reason for the antibacterial activity of BioTe, rather than ROS production and DNA damage. Moreover, a comparison of transcriptome and relative phenotypes reveals the difference in antibacterial mechanisms between BioTe and tellurite. Based on our evidence, we propose an antibacterial mode of rod-shaped BioTe, in which positively charged BioTe interact with the cell membrane through electrostatic attraction and then penetrate the membrane by using their sharp ends. In contrast, tellurite toxicity might be involved in sulfur metabolism.

Tolerance, Adaptation, and Cell Response Elicited by Micromonospora sp. Facing Tellurite Toxicity: A Biological and Physical-Chemical Characterization.

The intense use of tellurium (Te) in industrial applications, along with the improper disposal of Te-derivatives, is causing their accumulation in the environment, where oxyanion tellurite (TeO32-) is the most soluble, bioavailable, and toxic Te-species. On the other hand, tellurium is a rare metalloid element whose natural supply will end shortly with possible economic and technological effects. Thus, Te-containing waste represents the source from which Te should be recycled and recovered. Among the explored strategies, the microbial TeO32- biotransformation into less toxic Te-species is the most appropriate concerning the circular economy. Actinomycetes are ideal candidates in environmental biotechnology. However, their exploration in TeO32- biotransformation is scarce due to limited knowledge regarding oxyanion microbial processing. Here, this gap was filled by investigating the cell tolerance, adaptation, and response to TeO32- of a Micromonospora strain isolated from a metal(loid)-rich environment. To this aim, an integrated biological, physical-chemical, and statistical approach combining physiological and biochemical assays with confocal or scanning electron (SEM) microscopy and Fourier-transform infrared spectroscopy in attenuated total reflectance mode (ATR-FTIR) was designed. Micromonospora cells exposed to TeO32- under different physiological states revealed a series of striking cell responses, such as cell morphology changes, extracellular polymeric substance production, cell membrane damages and modifications, oxidative stress burst, protein aggregation and phosphorylation, and superoxide dismutase induction. These results highlight this Micromonospora strain as an asset for biotechnological purposes.

The putative phosphate transporter PitB (PP1373) is involved in tellurite uptake in Pseudomonas putida KT2440.

Tellurium oxyanions are chemical species of great toxicity and their presence in the environment has increased because of mining industries and photovoltaic and electronic waste. Recovery strategies for this metalloid that are based on micro-organisms are of interest, but further studies of the transport systems and enzymes responsible for implementing tellurium transformations are required because many mechanisms remain unknown. Here, we investigated the involvement in tellurite uptake of the putative phosphate transporter PitB (PP1373) in soil bacterium Pseudomonas putida KT2440. For this purpose, through a method based on the CRISPR/Cas9 system, we generated a strain deficient in the pitB gene and characterized its phenotype on exposing it to varied concentrations of tellurite. Growth curves and transmission electronic microscopy experiments for the wild-type and ΔpitB strains showed that both were able to internalize tellurite into the cytoplasm and reduce the oxyanion to black nano-sized and rod-shaped tellurium particles, although the ΔpitB strain showed an increased resistance to the tellurite toxic effects. At a concentration of 100 µM tellurite, where the biomass formation of the wild-type strain decreased by half, we observed a greater ability of ΔpitB to reduce this oxyanion with respect to the wild-type strain (~38 vs ~16 %), which is related to the greater biomass production of ΔpitB and not to a greater consumption of tellurite per cell. The phenotype of the mutant was restored on over-expressing pitB in trans. In summary, our results indicate that PitB is one of several transporters responsible for tellurite uptake in P. putida KT2440.

UV-Induced Redox Conversion of Tellurite by Biacetyl.

Tellurium (Te) is a rare element of great value, but it exists mainly in the toxic form of tellurite (TeIV) in water. Effective approaches that are able to reduce the toxicity and recover Te from contaminated water are highly needed. Here, we developed a simple but effective way to reduce toxic TeIV to widely applicable elemental Te0. With the combination of ultraviolet (UV) and biacetyl (BD), the oxidation state of Te could be feasibly changed from IV to 0 or VI. The consumption of dissolved oxygen (DO) was a key factor in the redox conversion of TeIV. Under UV irradiation, BD was first cleaved to acetyl radicals, which could then combine with water molecules to form more reductive diol radicals or combine with DO to form strongly oxidative peroxide radicals. Even without deoxygenation, the UV/BD system could rapidly change from being oxidative to being reductive because of the fast depletion of DO. Owing to the high quantum yield of the acetyl radical, the reduction efficiency of the UV/BD system was about 1 order of magnitude higher than that of UV/sulfite and was more efficient than the commonly used biological methods. This work provides a proof of concept for the reduction of tellurite, which could have relevant implications for water treatment and resource recovery applications.

Tellurium: A Rare Element with Influence on Prokaryotic and Eukaryotic Biological Systems.

Metalloid tellurium is characterized as a chemical element belonging to the chalcogen group without known biological function. However, its compounds, especially the oxyanions, exert numerous negative effects on both prokaryotic and eukaryotic organisms. Recent evidence suggests that increasing environmental pollution with tellurium has a causal link to autoimmune, neurodegenerative and oncological diseases. In this review, we provide an overview about the current knowledge on the mechanisms of tellurium compounds' toxicity in bacteria and humans and we summarise the various ways organisms cope and detoxify these compounds. Over the last decades, several gene clusters conferring resistance to tellurium compounds have been identified in a variety of bacterial species and strains. These genetic determinants exhibit great genetic and functional diversity. Besides the existence of specific resistance mechanisms, tellurium and its toxic compounds interact with molecular systems, mediating general detoxification and mitigation of oxidative stress. We also discuss the similarity of tellurium and selenium biochemistry and the impact of their compounds on humans.

Theoretical Investigation of an Alcohol-Filled Tellurite Photonic Crystal Fiber Temperature Sensor Based on Four-Wave Mixing.

For this study, a temperature sensor utilizing a novel tellurite photonic crystal fiber (PCF) is designed. In order to improve the sensor sensitivity, alcohol is filled in the air holes of the tellurite PCF. Based on the degenerate four-wave mixing theory, temperature sensing in the mid-infrared region (MIR) can be achieved by detecting the wavelength shift of signal waves and idler waves during variations in temperature. Simulation results show that at a pump wavelength of 3550 nm, the temperature sensitivity of this proposed sensor can be as high as 0.70 nm/°C. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on four-wave mixing (FWM) in a non-silica PCF.

Characterisation of STEC and other diarrheic E. coli isolated on CHROMagar™STEC at a tertiary referral hospital, Cape Town.

BACKGROUND: Shiga toxin producing E. coli (STEC) is an emerging zoonotic pathogen that can cause acute renal failure, especially in children. Clinical microbiology laboratories may fail to detect STEC and other diarrhoeic E. coli unless purposive rigorous screening procedures are followed using appropriate diagnostic technology; CHROMagar™STEC has rarely been used for isolation of African diarrhoeic E. coli hence characteristics of isolates on this medium are not yet fully understood. This study aimed to determine the prevalence and characteristics of STEC and other diarrhoeic E. coli isolated on CHROMagar™STEC from stool samples submitted to the microbiology laboratory of a South African public sector tertiary care hospital. RESULTS: In total, 733 stool samples were tested. Of these, 4.5% (33/733) possessed diarrhoeic E. coli. Of the diarrheic E. coli, 5/33 (15.2%) were STEC, 15/33 (45.5%) EAggEC, 6/33 (18.2%) atypical EPEC, 5/33 (15.2%) typical EPEC, and 1/33 (3%) DAEC. None of the STEC isolates had been identified by routine testing (based on using sorbitol media to test for E. coli O157: H7 strains and not the other STEC) in the laboratory. Of the 33 strains, 55% (95% CI = 40.8-72.7) showed resistance to ampicillin. CONCLUSIONS: CHROMagar™STEC enabled detection of tellurite - resistant diarrhoeic E. coli that would be missed using routine methods. Further studies are needed to determine the proportion and characteristics of those which might have been missed using this approach.

A comparative analysis of tellurite detoxification by members of the genus Shewanella.

The increasing industrial utilization of tellurium has resulted in an important environmental pollution with the soluble, extremely toxic oxyanion tellurite. In this context, the use of microorganisms for detoxifying tellurite or tellurium biorecovery has gained great interest. The ability of different Shewanella strains to reduce tellurite to elemental tellurium was assessed; the results showed that the reduction process is dependent on electron transport and the ∆pH gradient. While S. baltica OS155 showed the highest tellurite resistance, S. putrefaciens was the most efficient in reducing tellurite. Moreover, pH-dependent tellurite transformation was associated with tellurium precipitation as tellurium dioxide. In summary, this work highlights the high tellurite reduction/detoxification ability exhibited by a number of Shewanella species, which could represent the starting point to develop friendly methods for the recovery of elemental tellurium (or tellurium dioxide).