Tellurite-dependent blackening of bacteria emerges from the dark ages

Environmental contextAlthough tellurium is a relatively rare element in the earth’s crust, its concentration in some niches can be naturally high owing to unique geology. Tellurium, as the oxyanion, is toxic to prokaryotes, and although prokaryotes have evolved resistance to tellurium, no universal mechanism exists. We review the interaction of tellurite with prokaryotes with a focus on those unique strains that thrive in environments naturally rich in tellurium. AbstractThe timeline of tellurite prokaryotic biology and biochemistry is now over 50 years long. Its start was in the clinical microbiology arena up to the 1970s. The 1980s saw the cloning of tellurite resistance determinants whil…

Stability of biogenic metal(loid) nanomaterials related to the colloidal stabilization theory of chemical nanostructures

In the last 15 years, the exploitation of biological systems (i.e. plants, bacteria, mycelial fungi, yeasts, and algae) to produce metal(loid) (Me)-based nanomaterials has been evaluated as eco-friendly and a cost-effective alternative to the chemical synthesis processes. Although the biological mechanisms of biogenic Me-nanomaterial (Bio-Me-nanomaterials) production are not yet completely elucidated, a key advantage of such bio-nanostructures over those chemically synthesized is related to their natural thermodynamic stability, with several studies ascribed to the presence of an organic layer surrounding these Bio-Me-nanostructures. Different macromolecules (e.g. proteins, peptides, lipids…

Cross-linked natural IntegroPectin films from citrus biowaste with intrinsic antimicrobial activity

AbstractPectin recovered via hydrodynamic cavitation (IntegroPectin) from lemon and grapefruit agri-food waste intrinsically containing antimicrobial bioactive substances (flavonoids, phenolic acids, terpenes, and terpenoids) was used to generate innovative and eco-compatible films that efficiently inhibit the growth of Gram-negative pathogens. Extensive characterization of films confirmed the presence of these substances, which differently interact with the polysaccharide polymer (pectin), plasticizer (glycerol), surfactant (Tween 60), and cross-linker (Ca2+), conferring to these films a unique structure. Besides, IntegroPectin-based films constitute versatile systems for the sustained, co…

Genome Sequence of Rhodococcus sp. Strain BCP1, a Biodegrader of Alkanes and Chlorinated Compounds

Rhodococcus sp. strain BCP1 (DSM 44980) co-metabolizes chlorinated compounds and mineralizes a broad range of alkanes being highly tolerant to these toxic chemicals. Here, we present the high-quality draft genome sequence of strain BCP1 consisting of 6,231,823 bp, with a G+C content of 70.4%, 5,902 protein-coding genes, and 58 RNAs genes. Rhodococcus genus comprises Gram-positive, non-sporulating, aerobic bacteria that are widely distributed in the environment (1). Rhodococcus sp. strain BCP1 (formerly: Rhodococcus aetherovorans strain BCP1, DSM 44980) was selected from an aerobic butane-utilizing consortium as the prevailing isolate able to co-metabolize chloroform, vinyl chloride and tric…

Identification of Resistance Genes and Response to Arsenic in Rhodococcus aetherivorans BCP1

This is the accepted manuscript of the paper "Identification of Resistance Genes and Response to Arsenic in Rhodococcus aetherivorans BCP1", published as final paper in "Frontiers in Microbiology Volume 10, 07 May 2019, Pages 888 https://doi.org/10.3389/fmicb.2019.00888”. Arsenic (As) ranks among the priority metal(loid)s that are of public health concern. In the environment, arsenic is present in different forms, organic or inorganic, featured by various toxicity levels. Bacteria have developed different strategies to deal with this toxicity involving different resistance genetic determinants. Bacterial strains of Rhodococcus genus, and more in general Actinobacteria p…

Physical–chemical properties of biogenic selenium nanostructures produced by stenotrophomonas maltophilia SeITE02 and ochrobactrum sp. MPV1

Stenotrophomonas maltophilia SeITE02 and Ochrobactrum sp. MPV1 were isolated from the rhizosphere soil of the selenium-hyperaccumulator legume Astragalus bisulcatus and waste material from a dumping site for roasted pyrites, respectively. Here, these bacterial strains were studied as cell factories to generate selenium-nanostructures (SeNS) under metabolically controlled growth conditions. Thus, a defined medium (DM) containing either glucose or pyruvate as carbon and energy source along with selenite (SeO23−) was tested to evaluate bacterial growth, oxyanion bioconversion and changes occurring in SeNS features with respect to those generated by these strains grown on rich media. Transmissi…

Processing of metals and metalloids by actinobacteria: Cell resistance mechanisms and synthesis of metal(loid)-based nanostructures

Metal(loid)s have a dual biological role as micronutrients and stress agents. A few geochemical and natural processes can cause their release in the environment, although most metal-contaminated sites derive from anthropogenic activities. Actinobacteria include high GC bacteria that inhabit a wide range of terrestrial and aquatic ecological niches, where they play essential roles in recycling or transforming organic and inorganic substances. The metal(loid) tolerance and/or resistance of several members of this phylum rely on mechanisms such as biosorption and extracellular sequestration by siderophores and extracellular polymeric substances (EPS), bioaccumulation, biotransformation, and me…

Lipid Nanocarriers-Loaded Nanocomposite as a Suitable Platform to Release Antibacterial and Antioxidant Agents for Immediate Dental Implant Placement Restorative Treatment

Immediate implant placement is a single-stage restorative approach for missing teeth widely used to overcome the ridge remodeling process occurring after dental extractions. The success of this procedure relies on opportune osseointegration in the surrounding tissues. To support this process, a multifunctional nanocomposite, to be applied in the fresh post-extraction socket, was here designed, prepared, and characterized. This formulation consists of quercetin (QRC)-loaded nanostructured lipid carriers (NLCs) entrapped in a chitosan-based solid matrix containing ciprofloxacin (CPX). QRC-NLCs were prepared by homogenization followed by high-frequency sonication, and thereafter this dispersio…

Biosynthesis of selenium-nanoparticles and -nanorods as a product of selenite bioconversion by the aerobic bacterium Rhodococcus aetherivorans BCP1

The wide anthropogenic use of selenium compounds represents the major source of selenium pollution world- wide, causing environmental issues and health concerns. Microbe-based strategies for metal removal/recovery have received increasing interest thanks to the association of the microbial ability to detoxify toxic metal/ metalloid polluted environments with the production of nanomaterials. This study investigates the tolerance and the bioconversion of selenite (SeO32−) by the aerobically grown Actinomycete Rhodococcus aetherivorans BCP1 in association with its ability to produce selenium nanoparticles and nanorods (SeNPs and SeNRs). The BCP1 strain showed high tolerance towards SeO32− with…

Towards a new treatment against polymicrobial infections: high antibacterial activity of lemon IntegroPectin against Pseudomonas aeruginosa and Escherichia coli

AbstractLemon IntegroPectin obtained via hydrodynamic cavitation of waste lemon peel in water only shows high antibacterial activity against two Gram-negative bacteria, Pseudomonas aeruginosa and Escherichia coli. The antibacterial effect against the ubiquitous pathogen P. aeruginosa was evaluated in terms of the minimal bactericidal (MBC) and minimal inhibitory concentration (MIC). Preliminary insight on the antibacterial mechanism of IntegroPectin originates from investigating its inhibitory activity against E. coli. Given the non-cytotoxic nature of citrus IntegroPectin and the ease of its reproducible production in large amounts, the route is open to the industrial development of a new …

Neuroprotective and Mitoprotective Effects of Lemon IntegroPectin on SH-SY5Y Cells

AbstractLemon IntegroPectin obtained via hydrodynamic cavitation of organic lemon processing waste in water shows significant neuroprotective activity in vitro, as first reported in this study investigating the effects of both lemon IntegroPectin and commercial citrus pectin on cell viability, cell morphology, reactive oxygen species (ROS) production and mitochondria perturbation induced by treatment of neuronal SH-SY5Y human cells with H2O2. Mediated by ROS including H2O2 and its derivatives, oxidative stress alters numerous cellular processes, including mitochondrial regulation and cell signaling, propagating cellular injury that leads to incurable neurodegenerative diseases. These result…

On the ability of perfluorohexane sulfonate (PFHxS) bioaccumulation by two Pseudomonas sp. strains isolated from PFAS‐contaminated environmental matrices

PFASs (perfluoroalkyl and polyfluoroalkyl substances) are highly fluorinated, aliphatic, synthetic compounds with high thermal and chemical stability as well as unique amphiphilic properties which make them ingredients in a range of industrial processes. PFASs have attracted consideration due to their persistence, toxicity and bioaccumulation tendency in the environment. Recently, attention has begun to be addressed to shorter-chain PFASs, such as perfluorohexane sulfonate [PFHxS], apparently less toxic to and more easily eliminated from lab animals. However, short-chain PFASs represent end-products from the transformation of fluorotelomers whose biotic breakdown reactions have not been ide…

Antimicrobial activity of biogenically produced spherical Se-nanomaterials embedded in organic material against Pseudomonas aeruginosa and Staphylococcus aureus strains on hydroxyapatite-coated surfaces

In an effort to prevent the formation of pathogenic biofilms on hydroxyapatite (HA)-based clinical devices and surfaces, we present a study evaluating the antimicrobial efficacy of Spherical biogenic Se-Nanostructures Embedded in Organic material (Bio Se-NEMO-S) produced by Bacillus mycoides SelTE01 in comparison with two different chemical selenium nanoparticle (SeNP) classes. These nanomaterials have been studied as potential antimicrobials for eradication of established HA-grown biofilms, for preventing biofilm formation on HA-coated surfaces and for inhibition of planktonic cell growth of Pseudomonas aeruginosa NCTC 12934 and Staphylococcus aureus ATCC 25923. Bio Se-NEMO resulted more e…

Identification and characterization of new prolylendopeptidases (PEPs) from Actinomycetes

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…

New neuroprotective effect of lemon integropectin on neuronal cellular model

Lemon IntegroPectin obtained via hydrodynamic cavitation of organic lemon processing waste in water shows significant neuroprotective activity in vitro, as first reported in this study investigating the effects of both lemon IntegroPectin and commercial citrus pectin on cell viability, cell morphology, reactive oxygen species (ROS) production, and mitochondria perturbation induced by treatment of neuronal SH-SY5Y human cells with H2O2. Mediated by ROS, including H2O2 and its derivatives, oxidative stress alters numerous cellular processes, such as mitochondrial regulation and cell signaling, propagating cellular injury that leads to incurable neurodegenerative diseases. These results, and t…

New biocides based on imidazolinium-functionalised hybrid mesoporous silica nanoparticles

Here, we report the development of a new biocide based on hybrid mesoporous silica nanoparticles (MSN). The MSN was synthesized by condensation method in emulsion followed by grafting with two different silylated ionic liquid moieties, namely butyl imidazolinium bromide and imidazolinium propansulfonate betaine. Features of nanoparticles were characterized by Thermogravimetry, Infrared and ss-NMR Spectroscopy, and Transmission Electron Microscopy. The antibacterial properties were tested against a Gram-positive bacterial strain previously isolated from artefacts of interest in the field of Cultural Heritage. Interestingly, the hybrid material presents an antibacterial activity higher than i…

Selenium and tellurium nanomaterials

Abstract Over the last 40 years, the rapid and exponential growth of nanotechnology led to the development of various synthesis methodologies to generate nanomaterials different in size, shape and composition to be applied in various fields. In particular, nanostructures composed of Selenium (Se) or Tellurium (Te) have attracted increasing interest, due to their intermediate nature between metallic and non-metallic elements, being defined as metalloids. Indeed, this key shared feature of Se and Te allows us the use of their compounds in a variety of applications fields, such as for manufacturing photocells, photographic exposure meters, piezoelectric devices, and thermoelectric materials, t…

Pectin: A Long-Neglected Broad-Spectrum Antibacterial.

First reported in the late 1930s and first partly explained in 1970, the antibacterial activity of pectin remained almost ignored until the late 1990s. The concomitant emergence of research on natural antibacterials and on new usages of pectin polysaccharides, including those in medicine widely researched in Russia, has led to a renaissance of research in the physiological properties of this uniquely versatile polysaccharide ubiquitous in plants and fruits. Collecting scattered information, this study provides an updated overview on the subtle factors affecting the behaviour of pectin as antimicrobial. Less degraded pectin extracted via acid-free routes, we argue in the conclusions, will so…

Biotechnology of Rhodococcus for the production of valuable compounds

Abstract Bacteria belonging to Rhodococcus genus represent ideal candidates for microbial biotechnology applications because of their metabolic versatility, ability to degrade a wide range of organic compounds, and resistance to various stress conditions, such as metal toxicity, desiccation, and high concentration of organic solvents. Rhodococcus spp. strains have also peculiar biosynthetic activities that contribute to their strong persistence in harsh and contaminated environments and provide them a competitive advantage over other microorganisms. This review is focused on the metabolic features of Rhodococcus genus and their potential use in biotechnology strategies for the production o…

Growth of Rhodococcus sp. strain BCP1 on gaseous n-alkanes: New metabolic insights and transcriptional analysis of two soluble di-iron monooxygenase genes

none 7 si Rhodococcus sp. strain BCP1 was initially isolated for its ability to grow on gaseous n-alkanes, which act as inducers for the co-metabolic degradation of low-chlorinated compounds. Here, both molecular and metabolic features of BCP1 cells grown on gaseous and short-chain n-alkanes (up to n-heptane) were examined in detail. We show that propane metabolism generated terminal and sub-terminal oxidation products such as 1- and 2-propanol, whereas 1-butanol was the only terminal oxidation product detected from n-butane metabolism. Two gene clusters, prmABCD and smoABCD—coding for Soluble Di-Iron Monooxgenases (SDIMOs) involved in gaseous n-alkanes oxidation—were detected in the BCP1 g…

A combined physical-chemical and microbiological approach to unveil the fabrication, provenance, and state of conservation of the Kinkarakawa-gami art.

AbstractKinkarakawa-gami wallpapers are unique works of art produced in Japan between 1870 and 1905 and exported in European countries, although only few examples are nowadays present in Europe. So far, neither the wallpapers nor the composing materials have been characterised, limiting the effective conservation–restoration of these artefacts accounting also for the potential deteriogen effects of microorganisms populating them. In the present study, four Kinkarakawa-gami wallpapers were analysed combining physical–chemical and microbiological approaches to obtain information regarding the artefacts’ manufacture, composition, dating, and their microbial community. The validity of these met…

A Comparative Analysis of Aquatic and Polyethylene-Associated Antibiotic-Resistant Microbiota in the Mediterranean Sea

Simple Summary In recent years, a growing interest has been devoted to the bacterial characterization of marine plastic debris. So far, a few publications have explored the composition of microbial communities on polyethylene (PE) waste items and the occurrence of antibiotic-resistant bacteria (ARB). The occurrence of ARB in natural matrices can contribute to the spread of antibiotic resistance genes (ARGs) among environmental bacteria. In this study, we compared the microbial composition and the presence of ARGs in water and PE fragments collected from a stream and the seawater in a coastal area of Northwestern Sicily. Our findings showed more ARGs on PE fragments than the corresponding wa…

Aerobic growth of Rhodococcus aetherivorans BCP1 using selected naphthenic acids as the sole carbon and energy sources

Naphthenic acids (NAs) are an important group of toxic organic compounds naturally occurring in hydrocarbon deposits. This work shows that Rhodococcus aetherivorans BCP1 cells not only utilize a mixture of eight different NAs (8XNAs) for growth but they are also capable of marked degradation of two model NAs, cyclohexanecarboxylic acid (CHCA) and cyclopentanecarboxylic acid (CPCA) when supplied at concentrations from 50 to 500 mgL−1 . The growth curves of BCP1 on 8XNAs, CHCA, and CPCA showed an initial lag phase not present in growth on glucose, which presumably was related to the toxic effects of NAs on the cell membrane permeability. BCP1 cell adaptation responses that allowed survi…

Conservation state of two paintings in the Santa Margherita cliff cave: role of the environment and of the microbial community

Abstract The conservation of ancient paintings sited in humid environments is an actual challenge for restorers, because it needs the knowledge of the materials the paintings are made up and of their interaction with a peculiar surrounding environment; thus, tailored procedures and strategies aimed at restoring and preserving paintings are necessary. The Santa Margherita’s cave in Castellammare del Golfo (Trapani, Italy) is a natural cave, containing the remains of paintings, in a poor state of conservation, belonging to an ancient church dated back to the Middle Age. The present manuscript reports the monitoring of environmental conditions (i.e., temperature and humidity) in a full year as…

Formulation of Mesoporous Silica Nanoparticles for Controlled Release of Antimicrobials for Stone Preventive Conservation

The biotic deterioration of artifacts of archaeological and artistic interest mostly relies on the action of microorganisms capable of thriving under the most disparate environmental conditions. Thus, to attenuate biodeterioration phenomena, biocides can be used by the restorers to prevent or slow down the microbial growth. However, several factors such as biocide half-life, its wash-out because of environmental conditions, and its limited time of action make necessary its application repeatedly, leading to negative economic implications. Sound and successful treatments are represented by controlled release systems (CRSs) based on porous materials. Here, we report on the design and developm…

Assembly, growth and conductive properties of tellurium nanorods produced by Rhodococcus aetherivorans BCP1

AbstractTellurite (TeO32−) is a hazardous and toxic oxyanion for living organisms. However, several microorganisms can bioconvert TeO32− into the less toxic form of elemental tellurium (Te0). Here, Rhodococcus aetherivorans BCP1 resting (non-growing) cells showed the proficiency to produce tellurium-based nanoparticles (NPs) and nanorods (NRs) through the bioconversion of TeO32−, depending on the oxyanion initial concentration and time of cellular incubation. Te-nanostructures initially appeared in the cytoplasm of BCP1 cells as spherical NPs, which, as the exposure time increased, were converted into NRs. This observation suggested the existence of an intracellular mechanism of TeNRs assem…

New Synthetic Nitro-Pyrrolomycins as Promising Antibacterial and Anticancer Agents

: Pyrrolomycins (PMs) are polyhalogenated antibiotics known as powerful biologically active compounds, yet featuring high cytotoxicity. The present study reports the antibacterial and antitumoral properties of new chemically synthesized PMs, where the three positions of the pyrrolic nucleus were replaced by nitro groups, aiming to reduce their cytotoxicity while maintaining or even enhancing the biological activity. Indeed, the presence of the nitro substituent in diverse positions of the pyrrole determined an improvement of the minimal bactericidal concentration (MBC) against Gram-positive (i.e., Staphylococcus aureus) or -negative (i.e., Pseudomonas aeruginosa) pathogen strains as compare…

Graphene Oxide Carboxymethylcellulose Nanocomposite for Dressing Materials.

Sore, infected wounds are a major clinical issue, and there is thus an urgent need for novel biomaterials as multifunctional constituents for dressings. A set of biocomposites was prepared by solvent casting using different concentrations of carboxymethylcellulose (CMC) and exfoliated graphene oxide (Exf-GO) as a filler. Exf-GO was first obtained by the strong oxidation and exfoliation of graphite. The structural, morphological and mechanical properties of the composites (CMCx/Exf-GO) were evaluated, and the obtained composites were homogenous, transparent and brownish in color. The results confirmed that Exf-GO may be homogeneously dispersed in CMC. It was found that the composite has an i…

Genome and phenotype microarray analyses of rhodococcus sp. BCP1 and rhodococcus opacus R7: Genetic determinants and metabolic abilities with environmental relevance

In this paper comparative genome and phenotype microarray analyses of Rhodococcus sp. BCP1 and Rhodococcus opacus R7 were performed. Rhodococcus sp. BCP1 was selected for its ability to grow on short-chain n-alkanes and R. opacus R7 was isolated for its ability to grow on naphthalene and on o-xylene. Results of genome comparison, includ- ing BCP1, R7, along with other Rhodococcus reference strains, showed that at least 30% of the genome of each strain presented unique sequences and only 50% of the predicted proteome was shared. To associate genomic features with metabolic capabilities of BCP1 and R7 strains, hundreds of different growth conditions were tested through Phenotype Microarray, b…

Untargeted Metabolomics Investigation on Selenite Reduction to Elemental Selenium by Bacillus mycoides SeITE01

Bacillus mycoides SeITE01 is an environmental isolate that transforms the oxyanion selenite (SeO32−) into the less bioavailable elemental selenium (Se0) forming biogenic selenium nanoparticles (Bio-SeNPs). In the present study, the reduction of sodium selenite (Na2SeO3) by SeITE01 strain and the effect of SeO32− exposure on the bacterial cells was examined through untargeted metabolomics. A time-course approach was used to monitor both cell pellet and cell free spent medium (referred as intracellular and extracellular, respectively) metabolites in SeITE01 cells treated or not with SeO32−. The results show substantial biochemical changes in SeITE01 cells when exposed to SeO32−. The initial u…

A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL&minus

Volatile Compounds of Lemon and Grapefruit IntegroPectin

An HS-SPME GC-MS analysis of the volatile compounds adsorbed at the outer surface of lemon and grapefruit pectins obtained via the hydrodynamic cavitation of industrial waste streams of lemon and grapefruit peels in water suggests important new findings en route to understanding the powerful and broad biological activity of these new pectic materials. In agreement with the ultralow degree of esterification of these pectins, the high amount of highly bioactive &alpha

Superior Antibacterial Activity of Integral Lemon Pectin Extracted via Hydrodynamic Cavitation

Abstract Pectin extracted via hydrodynamic cavitation in water only from waste lemon peel and further isolated via freeze drying displays significant antibacterial activity against Staphylococcus aureus, a Gram positive pathogen which easily contaminates food. The antibacterial effect of the new IntegroPectin is largely superior to that of commercial citrus pectin, opening the way to advanced applications of a new bioproduct now obtainable in large amounts and at low cost from citrus juice industry's waste.

Antibacterial PEGylated Solid Lipid Microparticles for Cosmeceutical Purpose: Formulation, Characterization, and Efficacy Evaluation

The development of efficacious means of delivering antioxidant polyphenols from natural sources for the treatment of skin diseases is of great interest for many cosmetic and pharmaceutical companies. Resveratrol (RSV) and Limonene (LIM) have been shown to possess good anti-inflammatory and antibacterial properties against Staphylococcus aureus infections responsible for many skin disorders, such as acne vulgaris. In this study, solid lipid microparticles are designed as composite vehicles capable of encapsulating a high amount of trans-RSV and enhancing its absorption through the stratum corneum. A microparticulate system based on mixture of PEGylate lipids, long-chain alcohols and LIM is a…

Flavonoids in Lemon and Grapefruit IntegroPectin

Abstract Following the analysis of terpenes present in new lemon and grapefruit “IntegroPectin” pectins obtained via the hydrodynamic cavitation of industrial lemon and grapefruit processing waste, the HPLC‐MS analysis of flavonoid and other phenolic compounds reveals the presence of eriocitrin, naringin, hesperidin and kaempferol typical of the respective citrus fruits. The pectic fibers rich in rhamnogalacturonan‐I regions act as chemical sponges adsorbing and concentrating at their outer surface highly bioactive citrus flavonoids and terpenes. These findings, together with the unique molecular structure of these new whole citrus pectins, provide preliminary insight into the broad‐scope b…

Biogenic Selenium Nanoparticles: A Fine Characterization to Unveil Their Thermodynamic Stability

Among the plethora of available metal(loid) nanomaterials (NMs), those containing selenium are interesting from an applicative perspective, due to their high biocompatibility. Microorganisms capable of coping with toxic Se-oxyanions generate mostly Se nanoparticles (SeNPs), representing an ideal and green alternative over the chemogenic synthesis to obtain thermodynamically stable NMs. However, their structural characterization, in terms of biomolecules and interactions stabilizing the biogenic colloidal solution, is still a black hole that impairs the exploitation of biogenic SeNP full potential. Here, spherical and thermodynamically stable SeNPs were produced by a metal(loid) tolerant Mic…

Influence of bacterial physiology on processing of selenite, biogenesis of nanomaterials and their thermodynamic stability

We explored how Ochrobactrum sp. MPV1 can convert up to 2.5 mM selenite within 120 h, surviving the challenge posed by high oxyanion concentrations. The data show that thiol-based biotic chemical reaction(s) occur upon bacterial exposure to low selenite concentrations, whereas enzymatic systems account for oxyanion removal when 2 mM oxyanion is exceeded. The selenite bioprocessing produces selenium nanomaterials, whose size and morphology depend on the bacterial physiology. Selenium nanoparticles were always produced by MPV1 cells, featuring an average diameter ranging between 90 and 140 nm, which we conclude constitutes the thermodynamic stability range for these nanostructures. Alternativ…

Antifouling Systems Based on a Polyhedral Oligomeric Silsesquioxane-Based Hexyl Imidazolium Salt Adsorbed on Copper Nanoparticles Supported on Titania

The reaction of octakis(3-chloropropyl)octasilsesquioxane with four equivalents of 1-hexylimidazole or 1-decylimidazole gave two products labelled as HQ-POSS (hexyl-imidazolium quaternized POSS) and DQ-POSS (decyl-imidazolium quaternized POSS) as regioisomer mixtures. An investigation of the biological activity of these two compounds revealed the higher antimicrobial performances of HQ-POSS against Gram-positive and Gram-negative microorganisms, proving its broad-spectrum activity. Due to its very viscous nature, HQ-POSS was adsorbed in variable amounts on the surface of biologically active oxides to gain advantages regarding the expendability of such formulations from an applicative perspe…

Chemogenic versus biogenic synthesis of Selenium nanoparticles: a structural characterization

Among the plethora of available metal- and metalloid-based nanomaterials (NMs), selenium nanostructures (SeNSs) are one of the most interesting from an applicative perspective due to their intermediate properties between metals and non-metals, as well as their high biocompatibility. In this regard, the capability of microorganisms to biotransform toxic Se-oxyanions – i.e., selenite (SeO32-) and selenate (SeO42-) – into their less bioavailable elemental forms [Se(0)], mostly generating Se nanoparticles (SeNPs), represents as a useful and green alternative over chemogenic synthesis allowing to obtain highly thermodynamically stable NMs. However, their structural characterization, in terms of …

Rhodococcus aetherivorans BCP1 as cell factory for the production of intracellular tellurium nanorods under aerobic conditions

Tellurite (TeO3 2−) is recognized as a toxic oxyanion to living organisms. However, mainly anaerobic or facultative-anaerobic microorganisms are able to tolerate and convert TeO3 2− into the less toxic and available form of elemental Tellurium (Te0), producing Te-deposits or Te-nanostructures. The use of TeO3 2−-reducing bacteria can lead to the decontamination of polluted environments and the development of “green-synthesis” methods for the production of nanomaterials. In this study, the tolerance and the consumption of TeO3 2− have been investigated, along with the production and characterization of Te-nanorods by Rhodococcus aetherivorans BCP1 grown under aerobic conditions. Aerobically …

Is Caretta Caretta a Carrier of Antibiotic Resistance in the Mediterranean Sea?

Sea turtles can be considered a sentinel species for monitoring the health of marine ecosystems, acting, at the same time, as a carrier of microorganisms. Indeed, sea turtles can acquire the microbiota from their reproductive sites and feeding, contributing to the diffusion of antibiotic-resistant strains to uncontaminated environments. This study aims to unveil the presence of antibiotic-resistant bacteria in (i) loggerhead sea turtles stranded along the coast of Sicily (Mediterranean Sea), (ii) unhatched and/or hatched eggs, (iii) sand from the turtles&rsquo

Ochrobactrum sp. MPV1 from a dump of roasted pyrites can be exploited as bacterial catalyst for the biogenesis of selenium and tellurium nanoparticles

Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles—both inside and outside the cells—characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have att…

Tunable photoluminescence properties of selenium nanoparticles: biogenic versus chemogenic synthesis

Abstract Various technological and biomedical applications rely on the ability of materials to emit light (photoluminescence [PL]), and, among them, metal nanoparticles (NPs) and semi-conductor Quantum Dots (QDs) represent ideal candidates as sensing probes and imaging tools, portraying better PL features than conventional organic dyes. However, the knowledge of PL behavior of semiconductor NPs – i.e., selenium; SeNPs – is still in its infancy, especially for those synthesized by microorganisms. Considering the essential role played by biogenic SeNPs as antimicrobial, anticancer, and antioxidant agents, or food supplements, their PL properties must be explored to take full advantage of them…