Yttrium immobilization through biomineralization with phosphate by the resistant strain Mesorhizobium qingshengii J19.

AIMS: Yttrium (Y) holds significant industrial and economic importance, being listed as a critical element on the European list of critical elements, thus emphasizing the high priority for its recovery. Bacterial strategies play a crucial role in the biorecovery of metals, offering a promising and environmentally friendly approach. Therefore, gaining a comprehensive understanding of the underlying mechanisms behind bacterial resistance, as well as the processes of bioaccumulation and biotransformation, is of paramount importance. METHODS AND RESULTS: A total of 207 Alphaproteobacteria strains from the University of Coimbra Bacteria Culture Collection were tested for Y-resistance. Among these, strain Mesorhizobium qingshengii J19 exhibited high resistance (up to 4 mM Y) and remarkable Y accumulation capacity, particularly in the cell membrane. Electron microscopy revealed Y-phosphate interactions, while X-ray diffraction identified Y(PO3)3·9H2O biocrystals produced by J19 cells. CONCLUSION: This study elucidates Y immobilization through biomineralization within phosphate biocrystals using M. qingshengii J19 cells.

Supporting early-career dementia researchers: Identifying support needs and ways forward via a European study.

INTRODUCTION: Early-career researchers contribute significantly to dementia research and clinical practice. However, a growing group of early-career dementia researchers (ECDRs) lack appropriate support throughout their careers. Thus, we aim to (i) explore support needs, (ii) determine recommendations, and (iii) set the agenda for organizations to better support ECDRs. METHODS: An iterative, explanatory sequential mixed-methods design was applied. First ECDRs' needs were identified using an online survey informed by the Vitae Researcher Development Framework. Next, priority areas were selected and explored qualitatively with ECDRs in two workshops, utilizing the World Café methodology. RESULTS: Sixty-five ECDRs throughout Europe completed the survey, with the majority reporting that greater support is needed in terms of funding and career opportunities, social support and well-being, and "wide-reaching" dissemination. DISCUSSION: Based on the findings, six recommendations for support organizations, funding bodies, and universities to better support ECDRs are formulated, each intended for specific target audiences. HIGHLIGHTS: This article reports on focal points of career-related support needed in doctoral education and postdoctoral employment to foster a healthier academic environment, including finance, work-life balance, dissemination of research findings, and supervision, both in general and in dementia fields specifically. Funding and resources were identified as a significant challenge, and there was a call for more long-term positions and transition funding for postdoctoral researchers. Early-career dementia researchers addressed the need for support in producing outputs for non-academic audiences, including people living with dementia. The importance of disseminating research to diverse audiences has long been recognized; thus, it is critical that early-career dementia researchers be supported in this effort. Recommendations were formulated for researcher support (organizations), funding bodies, and universities. These recommendations include providing support for disseminating research to non-academic audiences, offering training in supervision skills, and promoting peer-to-peer mentoring and social activities for early-career dementia researchers.

How are early-career dementia researchers considered and supported on a national level by dementia plans and organizations? An overview of global policy approaches.

INTRODUCTION: Despite representing an essential workforce, it is unclear how global policy efforts target early-career dementia researchers (ECDRs). Thus, this study aimed to provide an overview of policies through which ECDRs are considered and supported by dementia plans and organizations. METHODS: G20 member states were evaluated for their national dementia plan alongside policies of leading dementia organizations. Data targeting support for ECDRs were extracted and subject to content analysis using inductive coding. Findings were categorized and narratively synthesized. RESULTS: Only China, Denmark, England, Greece, Northern Ireland, Scotland, Spain, and the United States mentioned ECDRs in their national plan. Additionally, 17 countries formalized ECDR support via dementia organizations. Support efforts included research funding, dissemination and networking, career development, and research advice. DISCUSSION: Few nations formally recognized ECDRs in dementia plans or through dementia organizations. To facilitate equal prospects for ECDRs, top-down approaches are urged to enhance and align their efforts. HIGHLIGHTS: Few G20 countries (8/46) had national dementia plans for early-career researchers. Targeted support comes from government and nongovernmental dementia organizations. Support includes funding, training, advice, research dissemination, and networking. Inconsistent definitions and eligibility criteria are barriers to accessing support. Global coordination and top-down policy will aid early-career dementia researchers.

Relevance of FeoAB system in Rhodanobacter sp. B2A1Ga4 resistance to heavy metals, aluminium, gallium, and indium.

Aluminium (Al), gallium (Ga), and indium (In) are metals widely used in diverse applications in industry, which consequently result in a source of environmental contamination. In this study, strain Rhodanobacter sp. B2A1Ga4, highly resistant to Al, Ga, and In, was studied to reveal the main effects of these metals on the strain and the bacterial mechanisms linked to the ability to cope with them. An indium-sensitive mutant obtained by random transposon mutagenesis has the feoA gene interrupted. This gene together with the feoB gene is part of the feo operon which encodes a ferrous uptake system (FeoAB). The mutant strain exhibited higher oxidative stress supported by a high concentration of reactive oxygen species (ROS) and low levels of reduced glutathione (GSH) in the presence of metals. The iron supplementation of the growth medium reverted the growth inhibition of the mutant strain caused by Ga and In, significantly reduced the ROS amounts in mutant cells grown in all conditions, and increased its GSH/total glutathione ratio to values similar to those of the native strain. Moreover, the mutant strain when submitted to In increased the production of siderophores. The genome sequence analysis of strain B2A1Ga4 showed a large number of genes encoding putative proteins involved in iron uptake from the cell surface to the cytoplasm. Understanding the bacteria-metal interactions linked to resistance to high-tech metals is relevant to future application of microorganisms in bioremediation and/or biorecovery processes of these metals. KEY POINTS: • The disruption of FeoAB system compromises the bacterial resistance to Al, Ga, and In. • The iron acquisition in Rhodanobacter sp. B2A1Ga4 controls the oxidative stress. • Genome mining of strain B2A1Ga4 reveals several iron transport related genes.

Arsenic accumulation by a rhizosphere bacterial strain Ochrobactrum tritici reduces rice plant arsenic levels.

Arsenic naturally occurs in the earth's crust and can be introduced in the environment by human activities. Agricultural practices in arsenic-contaminated environments pose a threat to human health. The contamination of crops contributes to the metalloid's introduction in the food chain. This study aims to test the hypotheses that the inoculation of a hyperaccumulator rhizobacterial strain, Ochrobactrum tritici As5, to the rhizosphere of rice plants reduces the arsenic presence inside the tissue of the rice plants and reduces the inhibitory effect of the metalloid on the plant's growth parameters. Inoculation of the hyperaccumulating strain O. tritici As5 showed the lowest concentration of arsenic in the plant's tissue (2.6 fold lower than sterile plants), compared to the unmodified type O. tritici SCII24 and sterile rice plants. The inoculation of the type strain SCII24 also led to a decrease in arsenic concentration in the plant tissue compared with sterile plants (1.6 fold lower than sterile plants). The difference in arsenic presence in shoots was smaller among treatment groups than in the roots, showing a similar trend. The inoculation of the hyperaccumulator As5 strain alleviated some of the toxic effects of arsenic on shoot growth compared to inoculation of the unmodified type strain. All these findings together, contribute to our understanding of the interplay between arsenic pollution, plants and their rhizobacteria, especially the role of bioaccumulation of metal(oids) by rhizobacteria, and provide important information on the prevention of arsenic uptake by crops and the development of phytostabilizers.

Increasing the Antimicrobial Activity of Amphiphilic Cationic Copolymers by the Facile Synthesis of High Molecular Weight Stars by Supplemental Activator and Reducing Agent Atom Transfer Radical Polymerization.

Infections caused by bacteria represent a great motif of concern in the health area. Therefore, there is a huge demand for more efficient antimicrobial agents. Antimicrobial polymers have attracted special attention as promising materials to prevent infectious diseases. In this study, a new polymeric system exhibiting antimicrobial activity against a range of Gram-positive and Gram-negative bacterial strains at micromolar concentrations (e.g., 0.8 µM) was developed. Controlled linear and star-shaped copolymers, comprising hydrophobic poly(butyl acrylate) (PBA) and cationic poly(3-acrylamidopropyl)trimethylammonium chloride) (PAMPTMA) segments, were obtained by supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) at 30 °C. The antibacterial activity of the polymers was studied by varying systematically the molecular weight (MW), hydrophilic/hydrophobic balance, and architecture. The MW was found to exert the greatest influence on the antimicrobial activity of the polymers, with minimum inhibitory concentration values decreasing with increasing MW. Live/dead membrane integrity assays and scanning electron microscopy analysis confirmed the bactericidal character of the synthesized PAMPTMA- (b)co-PBA polymers.

Two plant-hosted whole-cell bacterial biosensors for detection of bioavailable Cr(VI).

Metal whole-cell biosensors (WCBs) have been reported as very useful tools to detect and quantify the presence of bioavailable fractions of certain metals in water and soil samples. In the current work, two bacterial WCBs able to report Cr(VI) presence and plants growing on Cr(VI)-enriched soil/medium were used to assess the potential transfer of this metal to organisms of higher trophic levels, and the risk of transfer to the food chain. To do it, the functionality of the WCBs within tissues of inoculated plants in contact with Cr(VI)-contaminated soil and water was studied in vitro and in a controlled greenhouse environment. One WCB was the previously described Ochrobactrum tritici pCHRGFP2 and the second, Nitrospirillum amazonense pCHRGFP2, is a newly engineered naturally-occurring endophytic microorganism. Three rice varieties (IAC 4440, BRS 6 CHUÍ, IRGA 425) and one maize variety (1060) were tested as hosts and subjected to Cr(VI) treatments (25 µM), with different results obtained. Inoculation of each WCB into plants exposed to Cr(VI) showed GFP expression within plant tissues. WCBs penetrated the root tissues and later colonized the shoots and leaves. In general, a higher fluorescence signal was detected in roots, together with a higher Cr content and denser WCB colonization. Best fluorescence intensities per plant biomass of shoots were obtained for plant host IRGA 425. Therefore, by analyzing colonized tissues, both WCBs allowed the detection of Cr(VI) contamination in soils and its transfer to plants commonly used in crops for human diet.

Impact of plant-associated bacteria biosensors on plant growth in the presence of hexavalent chromium.

Cr(VI) is a highly toxic metal produced by anthropogenic activity which may impact the environment, affecting plants and animals. In plants, chromium both as Cr(III) or Cr(VI) can be absorbed by roots, is poorly translocated and affects negatively plant growth. Plants used in phytoremediation need to cope with chromium toxicity. This work aimed to evaluate strains of Ochrobactrum tritici and Nitrospirillum amazonense, resistant and modified in order to become chromate whole-cell biosensors, as plant-protectors enabling plants to withstand contaminated soils. In vitro tests were performed in three rice varieties and one maize variety. Initial evaluations of Cr(VI) toxicity to plants showed that plants had different sensitivities and BRS 6 CHUÍ rice variety was the most resistant. The metal affected plant growth and development, essentially in roots which were totally inhibited in rice varieties at 500 µM. This effect was plant-dependent. Modified N. amazonense proved to protect maize plants independently of the inoculation dose but O. tritici showed plant specificity and some toxicity when inoculated at high numbers, inhibiting rice development but not maize. Inoculants were directly responsible for growth improvements of specific plant varieties at 1.25 ppm Cr(VI), a concentration which corresponds to a weak soil contamination. Improvements were observed relatively to the Cr(VI)-treated controls, but also relative to the untreated controls, i.e., the benefits went beyond a simple neutralization of inhibition brought by Cr(VI) toxicity.

Two superoxide dismutases from TnOtchr are involved in detoxification of reactive oxygen species induced by chromate.

BACKGROUND: Superoxide dismutases (SOD) have been reported as the most relevant bacterial enzymes involved in cells protection from reactive oxygen species (ROS). These toxic species are often the product of heavy metal stress. RESULTS: Two genes, chrC and chrF, from TnOtchr genetic determinant of strain Ochrobactrum tritici 5bvl1 were cloned in Escherichia coli in order to overexpress the respective proteins. Both proteins were purified and characterized as superoxide dismutases. ChrC was confirmed as being a Fe-SOD, and the enzymatic activity of the ChrF, not inhibited by hydrogen peroxide or potassium cyanide, suggested its inclusion in the Mn-SOD family. This identification was supported by chemical quantification of total metal content in purified enzyme. Both enzymes showed a maximum activity between pH 7.2-7.5. ChrF retained nearly full activity over a broader range of pH and was slightly more thermostable than ChrC. The genes encoding these enzymes in strain O. tritici 5bvl1 were inactivated, developing single and double mutants, to understand the contribution of these enzymes in detoxification mechanism of reactive oxygen species induced by chromate. During chromate stress, assays using fluorescent dyes indicated an increase of these toxic compounds in chrC, chrF and chrC/chrF mutant cells. CONCLUSIONS: In spite of the multiple genes coding for putative superoxide dismutase enzymes detected in the genome of O. tritici 5bvl1, the ChrC and ChrF might help the strain to decrease the levels of reactive oxygen species in cells.

Natural hot spots for gain of multiple resistances: arsenic and antibiotic resistances in heterotrophic, aerobic bacteria from marine hydrothermal vent fields.

Microorganisms are responsible for multiple antibiotic resistances that have been associated with resistance/tolerance to heavy metals, with consequences to public health. Many genes conferring these resistances are located on mobile genetic elements, easily exchanged among phylogenetically distant bacteria. The objective of the present work was to isolate arsenic-, antimonite-, and antibiotic-resistant strains and to determine the existence of plasmids harboring antibiotic/arsenic/antimonite resistance traits in phenotypically resistant strains, in a nonanthropogenically impacted environment. The hydrothermal Lucky Strike field in the Azores archipelago (North Atlantic, between 11°N and 38°N), at the Mid-Atlantic Ridge, protected under the OSPAR Convention, was sampled as a metal-rich pristine environment. A total of 35 strains from 8 different species were isolated in the presence of arsenate, arsenite, and antimonite. ACR3 and arsB genes were amplified from the sediment's total DNA, and 4 isolates also carried ACR3 genes. Phenotypic multiple resistances were found in all strains, and 7 strains had recoverable plasmids. Purified plasmids were sequenced by Illumina and assembled by EDENA V3, and contig annotation was performed using the "Rapid Annotation using the Subsystems Technology" server. Determinants of resistance to copper, zinc, cadmium, cobalt, and chromium as well as to the antibiotics ß-lactams and fluoroquinolones were found in the 3 sequenced plasmids. Genes coding for heavy metal resistance and antibiotic resistance in the same mobile element were found, suggesting the possibility of horizontal gene transfer and distribution of theses resistances in the bacterial population.

Assessment of antimicrobial resistance, biofilm formation, and surface modification potential in hospital strains of Pseudomonas aeruginosa and Klebsiella pneumoniae.

The occurrence of healthcare-associated infections is a multifactorial phenomenon related to hospital space contamination by bacteria. The ESKAPE group, specifically Pseudomonas aeruginosa and Klebsiella pneumoniae, play a relevant role in the occurrence of these infections. Therefore, comprehensive research is needed to identify characteristics that justify the prevalence of these species in the healthcare environment. In this line, the study aimed to determine the antimicrobial resistance, biofilm formation, and the potential for polymer degradation in a collection of 33 P. aeruginosa strains and 2 K. pneumoniae strains sampled from various equipment and non-critical surfaces in a Portuguese hospital. Antimicrobial susceptibility tests revealed that none of the strains was categorized as multidrug-resistant (non-MDR). An assessment of their biofilm-forming capabilities indicated that 97 % of the strains exhibited biofilm-producing characteristics. Notably, within this group, the majority of P. aeruginosa and half of K. pneumoniae strains were classified as strong biofilm producers. Furthermore, the strains were evaluated for their potential to cause damage or change medical devices, namely infusion sets, nasal cannula, and urinary catheters. Three P. aeruginosa strains, two strong and one moderate biofilm producers, showed the highest ability to modify surfaces of the nasal cannula and infusion sets. Additionally, the Chi-square test revealed a statistically significant relationship between the presence of P. aeruginosa strains and the water accession spots. In conclusion, this work suggests that bacteria from this group hold a significant ability to grow in the healthcare environment through the degradation of non-critical materials. This suggests a potential concern for the persistence and proliferation of these organisms in hospital environments, emphasizing the importance of robust infection control measures to mitigate the risks associated with bacterial growth on such surfaces.

Exploring long-term retention and reactivation of micropollutant biodegradation capacity.

The factors limiting micropollutant biodegradation in the environment and how to stimulate this process have often been investigated. However, little information is available on the capacity of microbial communities to retain micropollutant biodegradation capacity in the absence of micropollutants or to reactivate micropollutant biodegradation in systems with fluctuating micropollutant concentrations. This study investigated how a period of 2 months without the addition of micropollutants and other organic carbon affected micropollutant biodegradation by a micropollutant-degrading microbial community. Stimulation of micropollutant biodegradation was performed by adding different types of dissolved organic carbon (DOC)-extracted from natural sources and acetate-increasing 10 × the micropollutant concentration, and inoculating with activated sludge. The results show that the capacity to biodegrade 3 micropollutants was permanently lost. However, the biodegradation activity of 2,4-D, antipyrine, chloridazon, and its metabolites restarted when these micropollutants were re-added to the community. Threshold concentrations similar to those obtained before the period of no substrate addition were achieved, but biodegradation rates were lower for some compounds. Through the addition of high acetate concentrations (108 mg-C/L), gabapentin biodegradation activity was regained, but 2,4-D biodegradation capacity was lost. An increase of bentazon concentration from 50 to 500 µg/L was necessary for biodegradation to be reactivated. These results provide initial insights into the longevity of micropollutant biodegradation capacity in the absence of the substance and strategies for reactivating micropollutant biodegrading communities.

Biostimulation with oxygen and electron donors supports micropollutant biodegradation in an experimentally simulated nitrate-reducing aquifer.

The availability of suitable electron donors and acceptors limits micropollutant natural attenuation in oligotrophic groundwater. This study investigated how electron donors with different biodegradability (humics, dextran, acetate, and ammonium), and different oxygen concentrations affect the biodegradation of 15 micropollutants (initial concentration of each micropollutant = 50 µg/L) in simulated nitrate reducing aquifers. Tests mimicking nitrate reducing field conditions showed no micropollutant biodegradation, even with electron donor amendment. However, 2,4-dichlorophenoxyacetic acid and mecoprop were biodegraded under (micro)aerobic conditions with and without electron donor addition. The highest 2,4-dichlorophenoxyacetic acid and mecoprop biodegradation rates and removal efficiencies were obtained under fully aerobic conditions with amendment of an easily biodegradable electron donor. Under microaerobic conditions, however, amendment with easily biodegradable dissolved organic carbon (DOC) inhibited micropollutant biodegradation due to competition between micropollutants and DOC for the limited oxygen available. Microbial community composition was dictated by electron acceptor availability and electron donor amendment, not by micropollutant biodegradation. Low microbial community richness and diversity led to the absence of biodegradation of the other 13 micropollutants (such as bentazon, chloridazon, and carbamazepine). Finally, adaptation and potential growth of biofilms interactively determined the location of the micropollutant removal zone relative to the point of amendment. This study provides new insight on how to stimulate in situ micropollutant biodegradation to remediate oligotrophic groundwaters as well as possible limitations of this process.

Sterilized Polyhexanide-Releasing Chitosan Membranes with Potential for Use in Antimicrobial Wound Dressings.

Wound infection is a common complication of chronic wounds. It can impair healing, which may not occur without external help. Antimicrobial dressings (AMDs) are a type of external help to infected chronic wounds. In this study, highly porous membranes made of only chitosan and containing the antiseptic polyhexanide (poly(hexamethylene biguanide); PHMB) were prepared by cryogelation, aiming to be used in AMDs. These membranes exhibited a water swelling capacity of 748%, a water drop penetration time of 11 s in a dry membrane and a water vapor transmission rate of 34,400 g H2O/m2/24 h when in contact with water. The best drug loading method involved simultaneous loading by soaking in a PHMB solution and sterilization by autoclaving, resulting in sterilized, drug-loaded membranes. When these membranes and a commercial PHMB-releasing AMD were assayed under the same conditions, albeit far from the in vivo conditions, their drug release kinetics were comparable, releasing PHMB for ca. 6 and 4 h, respectively. These membranes exhibited high antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, which are bacterial species commonly found in infected wounds and blood clotting activity. The obtained results suggest that these membranes may have potential for use in the development of AMDs.

Influence of redox condition and inoculum on micropollutant biodegradation by soil and activated sludge communities.

Micropollutant biodegradation is selected by the interplay among environmental conditions and microbial community composition. This study investigated how different electron acceptors, and different inocula with varying microbial diversity, pre-exposed to distinct redox conditions and micropollutants, affect micropollutant biodegradation. Four tested inocula comprised of agricultural soil (Soil), sediment from a ditch in an agricultural field (Ditch), activated sludge from a municipal WWTP (Mun AS), and activated sludge from an industrial WWTP (Ind AS). Removal of 16 micropollutants was investigated for each inoculum under aerobic, nitrate reducing, iron reducing, sulfate reducing, and methanogenic conditions. Micropollutant biodegradation was highest under aerobic conditions with removal of 12 micropollutants. Most micropollutants were biodegraded by Soil (n = 11) and Mun AS inocula (n = 10). A positive correlation was observed between inoculum community richness and the number of different micropollutants a microbial community initially degraded. The redox conditions to which a microbial community had been exposed appeared to positively affect micropollutant biodegradation performance more than pre-exposure to micropollutants. Additionally, depletion of the organic carbon present in the inocula resulted in lower micropollutant biodegradation and overall microbial activities, suggesting that i) an additional carbon source is needed to promote micropollutant biodegradation; and ii) overall microbial activity can be a good indirect indicator for micropollutant biodegradation activity. These results could help to develop novel micropollutant removal strategies.

Genome mining to unravel potential metabolic pathways linked to gallium bioleaching ability of bacterial mine isolates.

Gallium (Ga) is considered a high-tech Critical Metal, used in the manufacture of several microelectronic components containing either gallium arsenide (GaAs) or gallium nitride (GaN). The current high demand for this critical metal urges the development of effective recovery processes from secondary resources such as mine tailings or electronic recycling material. The importance of bioleaching as a biotechnological process to recover metals prompted this study, where an integrative approach combining experimental and genomic analysis was undertaken to identify potential mechanisms involved in bioleaching ability and strategies to cope with high metal(loid)s concentrations in five mine isolates. The Clusters of Orthologous Group (COG) annotation showed that the "amino acid transport and metabolism" [E] was the most predominant functional category in all genomes. In addition, the KEEG pathways analysis also showed predicted genes for the biosynthetic pathways of most amino acids, indicating that amino acids could have an important role in the Ga leaching mechanism. The presence of effective resistance mechanisms to Ga and arsenic (As) was particularly important in GaAs bioleaching batch assays, and might explain the divergence in bioleaching efficiency among the bacterial strains. Rhodanobacter sp. B2A1Ga4 and Sphingomonas sp. A2-49 with higher resistance, mainly to As, were the most efficient bioleaching strains under these conditions. In bioleaching assays using cell-free spent medium Arthrobacter silviterrae A2-55 with lower As resistance outperformed all the other stains. Overall, higher efficiency in Ga leaching was obtained in bioleaching assays using GaAs when compared to GaN.

Post-measurement compressed calibration for ICP-MS-based metal quantification in mine residues bioleaching.

Bioleaching is an actual economical alternative to treat residues, which allows, depending on the chosen strategy, two possible outcomes: (1) a leachate enriched with target metals, or (2) a residue enriched in target metals through the leaching of interfering components (IC). This work aimed to study the metals released by bioprocessing the Panasqueira mine tailings, as a strategy to increase critical metals' relative concentration in residues. Biostimulation of the local microbiota was compared to a bioaugmentation approach using the autochthonous Diaphorobacter polyhydroxybutyrativorans strain B2A2W2. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was selected to study the metals released in the leachate through multi-element external standards. A new data treatment method was developed to use a preliminary sweep of intensities to quantify the non-initial target metals concentration in the leachate, based on preliminary ICP-MS intensity measurements. The results demonstrated that biostimulation was an efficient bioleaching strategy for the IC silicon, aluminium, magnesium, selenium, manganese, zinc, iron, and copper, by decreasing concentration, resulting in a relative increase in the gallium and yttrium (10x) levels in the treated residue. The strategy followed to quantify a large number of elements with ICP-MS using a reduced number of data points for calibration proved valid and speeded up the analytical process.

Evaluation of the Microbiological Effectiveness of Three Accessible Mask Decontamination Methods and Their Impact on Filtration, Air Permeability and Physicochemical Properties.

The need to secure public health and mitigate the environmental impact associated with the massified use of respiratory protective devices (RPD) has been raising awareness for the safe reuse of decontaminated masks by individuals and organizations. Among the decontamination treatments proposed, in this work, three methods with the potential to be adopted by households and organizations of different sizes were analysed: contact with nebulized hydrogen peroxide (H2O2); immersion in commercial bleach (NaClO) (sodium hypochlorite, 0.1% p/v); and contact with steam in microwave steam-sanitizing bags (steam bag). Their decontamination effectiveness was assessed using reference microorganisms following international standards (issued by ISO and FDA). Furthermore, the impact on filtration efficiency, air permeability and several physicochemical and structural characteristics of the masks, were evaluated for untreated masks and after 1, 5 and 10 cycles of treatment. Three types of RPD were analysed: surgical, KN95, and cloth masks. Results demonstrated that the H2O2 protocol sterilized KN95 and surgical masks (reduction of >6 log10 CFUs) and disinfected cloth masks (reduction of >3 log10 CFUs). The NaClO protocol sterilized surgical masks, and disinfected KN95 and cloth masks. Steam bags sterilized KN95 and disinfected surgical and cloth masks. No relevant impact was observed on filtration efficiency.

Chromium resistance strategies and toxicity: what makes Ochrobactrum tritici 5bvl1 a strain highly resistant.

Large-scale industrial use of chromium (Cr) resulted in widespread environmental contamination with hexavalent chromium (Cr(VI)). The ability of microorganisms to survive in these environments and detoxify chromate requires the presence of specific resistance systems. Several Cr(VI) resistant species, belonging to a variety of genera, have been isolated in recent years. Ochrobactrum tritici strain 5bvl1 is a model for a highly Cr(VI)-resistant and reducing microorganism, with different strategies to cope with chromium. The strain contains the transposon-located (TnOtChr) chromate resistance genes chrB, chrA, chrC, chrF. The chrB and chrA genes were found to be essential for the establishment of high resistance but not chrC or chrF genes. Other mechanisms involved in chromium resistance in this strain were related to strategies such as specific or unspecific Cr(VI) reduction, free-radical detoxifying activities, and repairing DNA damage. Expression of the chrB, chrC or chrF genes was related to increased resistance to superoxide-generating agents. Genetic analyses also showed that, the ruvB gene is related to chromium resistance in O. tritici 5bvl1. The RuvABC complex probably does not form when ruvB gene is interrupted, and the repair of DNA damage induced by chromium is prevented. Aerobic or anaerobic chromate reductase activity and other unspecific mechanisms for chromium reduction have been identified in different bacteria. In the strain O. tritici 5bvl1, several unspecific mechanisms were found. Dichromate and chromate have different effects on the physiology of the chromium resistant strains and dichromate seems to be more toxic. Toxicity of Cr(VI) was evaluated by following growth, reduction, respiration, glucose uptake assays and by comparing cell morphology.

A DedA Family Membrane Protein in Indium Extrusion in Rhodanobacter sp. B2A1Ga4.

Indium (In) is a critical metal widely used in electronic equipment, and the supply of this precious metal is a major challenge for sustainable development. The use of microorganisms for the recovery of this critical high-tech element has been considered an excellent eco-friendly strategy. The Rhodanobacter sp. B2A1Ga4 strain, highly resistant to In, was studied in order to disclose the bacterial mechanisms closely linked to the ability to cope with this metal. The mutation of the gene encoding for a DedA protein homolog, YqaA, affected drastically the In resistance and the cellular metabolic activity of strain Rhodanobacter sp. B2A1Ga4 in presence of this metal. This indicates that this protein plays an important role in its In resistance phenotype. The negative impact of In might be related to the high accumulation of the metal into the mutant cells showing In concentration up to approximately 4-fold higher than the native strain. In addition, the expression of the yqaA gene in this mutant reverted the bacterial phenotype with a significant decrease of In accumulation levels into the cells and an increase of In resistance. Membrane potential measurements showed similar values for native and mutant cells, suggesting that there was no loss of proton-motive force in the mutant cells. The results from this study suggest a potential role of this DedA family protein as a membrane transporter involved in the In efflux process. The mutant strain also has the potential to be used as a biotool in bioaccumulation strategies, for the recovery of In in biomining activities.