Biosynthesis of photostable CdS quantum dots by UV-resistant psychrotolerant bacteria isolated from Union Glacier, Antarctica.

BACKGROUND: Quantum Dots (QDs) are fluorescent nanoparticles with exceptional optical and optoelectronic properties, finding widespread utility in diverse industrial applications. Presently, chemically synthesized QDs are employed in solar cells, bioimaging, and various technological domains. However, many applications demand QDs with prolonged lifespans under conditions of high-energy radiation. Over the past decade, microbial biosynthesis of nanomaterials has emerged as a sustainable and cost-effective process. In this context, the utilization of extremophile microorganisms for synthesizing QDs with unique properties has recently been reported. RESULTS: In this study, UV-resistant bacteria were isolated from one of the most extreme environments in Antarctica, Union Glacier at the Ellsworth Mountains. Bacterial isolates, identified through 16 S sequencing, belong to the genera Rhodococcus, Pseudarthrobacter, and Arthrobacter. Notably, Rhodococcus sp. (EXRC-4 A-4), Pseudarthrobacter sp. (RC-2-3), and Arthrobacter sp. (EH-1B-1) tolerate UV-C radiation doses ≥ 120 J/m². Isolated UV-resistant bacteria biosynthesized CdS QDs with fluorescence intensities 4 to 8 times higher than those biosynthesized by E. coli, a mesophilic organism tolerating low doses of UV radiation. Transmission electron microscopy (TEM) analysis determined QD sizes ranging from 6 to 23 nm, and Fourier-transform infrared (FTIR) analysis demonstrated the presence of biomolecules. QDs produced by UV-resistant Antarctic bacteria exhibit high photostability after exposure to UV-B radiation, particularly in comparison to those biosynthesized by E. coli. Interestingly, red fluorescence-emitting QDs biosynthesized by Rhodococcus sp. (EXRC-4 A-4) and Arthrobacter sp. (EH-1B-1) increased their fluorescence emission after irradiation. Analysis of methylene blue degradation after exposure to irradiated QDs biosynthesized by UV-resistant bacteria, indicates that the QDs transfer their electrons to O2 for the formation of reactive oxygen species (ROS) at different levels. CONCLUSIONS: UV-resistant Antarctic bacteria represent a novel alternative for the sustainable generation of nanostructures with increased radiation tolerance-two characteristics favoring their potential application in technologies requiring continuous exposure to high-energy radiation.

Minicells as an Escherichia coli mechanism for the accumulation and disposal of fluorescent cadmium sulphide nanoparticles.

BACKGROUND: Bacterial biosynthesis of fluorescent nanoparticles or quantum dots (QDs) has emerged as a unique mechanism for heavy metal tolerance. However, the physiological pathways governing the removal of QDs from bacterial cells remains elusive. This study investigates the role of minicells, previously identified as a means of eliminating damaged proteins and enhancing bacterial resistance to stress. Building on our prior work, which unveiled the formation of minicells during cadmium QDs biosynthesis in Escherichia coli, we hypothesize that minicells serve as a mechanism for the accumulation and detoxification of QDs in bacterial cells. RESULTS: Intracellular biosynthesis of CdS QDs was performed in E. coli mutants ΔminC and ΔminCDE, known for their minicell-producing capabilities. Fluorescence microscopy analysis demonstrated that the generated minicells exhibited fluorescence emission, indicative of QD loading. Transmission electron microscopy (TEM) confirmed the presence of nanoparticles in minicells, while energy dispersive spectroscopy (EDS) revealed the coexistence of cadmium and sulfur. Cadmium quantification through flame atomic absorption spectrometry (FAAS) demonstrated that minicells accumulated a higher cadmium content compared to rod cells. Moreover, fluorescence intensity analysis suggested that minicells accumulated a greater quantity of fluorescent nanoparticles, underscoring their efficacy in QD removal. Biosynthesis dynamics in minicell-producing strains indicated that biosynthesized QDs maintained high fluorescence intensity even during prolonged biosynthesis times, suggesting continuous QD clearance in minicells. CONCLUSIONS: These findings support a model wherein E. coli utilizes minicells for the accumulation and removal of nanoparticles, highlighting their physiological role in eliminating harmful elements and maintaining cellular fitness. Additionally, this biosynthesis system presents an opportunity for generating minicell-coated nanoparticles with enhanced biocompatibility for diverse applications.

Solid medium for the direct isolation of bacterial colonies growing with polycyclic aromatic hydrocarbons or 2,4,6-trinitrotoluene (TNT).

Isolation of hydrocarbon-degrading bacteria is a key step for the study of microbiological diversity, metabolic pathways, and bioremediation. However current strategies lack simplicity and versatility. We developed an easy method for the screening and isolation of bacterial colonies capable of degrading hydrocarbons, such as diesel or polycyclic aromatic hydrocarbons (PAHs), as well as the pollutant explosive, 2,4,6-trinitrotoluene (TNT). The method uses a two-layer solid medium, with a layer of M9 medium, and a second layer containing the carbon source deposited through the evaporation of ethanol. Using this medium we grew hydrocarbon-degrading strains, as well as TNT-degrading isolates. We were able to isolate PAHs-degrading bacterial colonies directly from diesel-polluted soils. As a proof of concept, we used this method to isolate a phenanthrene-degrading bacteria, identified as Acinetobacter sp. and determined its ability to biodegrade this hydrocarbon.

Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., two new species with the ability to degrade TNT isolated from soil samples at Deception Island, maritime Antarctica.

Two motile, rod-shaped, Gram-stain-negative bacterial strains, TNT11T and TNT19T, were isolated from soil samples collected at Deception Island, Antarctica. According to the 16S rRNA gene sequence similarity, both strains belong to the genus Pseudomonas. Further genomic analyses based on ANI and dDDH suggested that these strains were new species. Growth of strain TNT11T is observed at 0-30 â„ƒ (optimum, 20 â„ƒ), pH 4.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum, 1% NaCl), while for TNT19T is observed at 0-30 â„ƒ (optimum between 15 and 20 â„ƒ), pH 5.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum between 0 and 1% NaCl). The fatty acid profile consists of the major compounds; C16:0 and C16:1 ω6 for TNT11T, and C16:0 and C12:0 for TNT19T. Based on the draft genome sequences, the DNA G + C content for TNT11T is 60.43 mol% and 58.60 mol% for TNT19T. Based on this polyphasic study, TNT11T and TNT19T represent two novel species of the genus Pseudomonas, for which the proposed names are Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., respectively. The type strains are Pseudomonas violetae TNT11T (= RGM 3443T = LMG 32959T) and Pseudomonas emilianonis TNT19T (= RGM 3442T = LMG 32960T). Strains TNT11T and TNT19T were deposited to CChRGM and BCCM/LMG with entry numbers RGM 3443/LMG 32959 and RGM 3442/LMG 32960, respectively.

Arthrobacter vasquezii sp. nov., isolated from a soil sample from Union Glacier, Antarctica.

A Gram-stain-positive, catalase-positive, non-motile bacteria, with a rod-coccus cycle (designated as EH-1B-1T) was isolated from a soil sample from Union Glacier in Ellsworth Mountains, Antarctica. Strain EH-1B-1T had an optimal growth temperature of 28 °C and grew at pH 7-10. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, C16 : 0 and anteiso-C17 : 0. The G+C content based on the whole genome sequence was 63.1 mol%. Strain EH-1B-1T was most closely related to members of the genus Arthrobacter, namely Arthrobacter subterraneus and Arthrobacter tumbae. The strain grew on tryptic soy agar, Reasoner's 2A agar, lysogeny broth agar and nutrient agar. The average nucleotide identity and digital DNA-DNA hybridization values between strain EH-1B-1T and its closest reference type strains ranged from 78 to 88 % and from 20.9 to 36.3 %, respectively. Based on phenotypic, chemotypic and genotypic evidence, it is proposed that strain EH-1B-1T represents a novel species of Arthrobacter, for which the name Arthrobacter vasquezii sp. nov. is proposed, with strain EH-1B-1T (RGM 3386T=LMG 32961T) as the type strain.

Development and assessment of a virtual escape-room game for teaching industrial bioprocesses.

This article presents a study on the implementation of a virtual escape-room game as a novel teaching methodology in biochemistry education. The game aimed to engage students in producing monoclonal antibodies against SARS-CoV-2 while reinforcing theoretical concepts and fostering teamwork. Three versions of the game were tested, incorporating modifications to address student feedback on and improve the overall experience. The study employed a satisfaction survey to gather insights from students regarding their perception of the game. Results showed that the implementation of answer flexibility using RegEx had a significant positive impact on student satisfaction and motivation. The introduction of RegEx allowed for a more realistic and immersive gaming experience, as students could provide varied answers while still being evaluated correctly. Overall, the findings highlight the effectiveness of the game's design, the suitability of the Google Forms platform for distance learning, and the importance of incorporating answer flexibility through RegEx. These results provide valuable guidance for educators seeking to enhance student engagement and satisfaction through the use of escape-room games in biochemistry education.

Biosynthesis of Cu-In-S Nanoparticles by a Yeast Isolated from Union Glacier, Antarctica: A Platform for Enhanced Quantum Dot-Sensitized Solar Cells.

In recent years, the utilization of extremophile microorganisms for the synthesis of metal nanoparticles, featuring enhanced properties and diverse compositions, has emerged as a sustainable strategy to generate high-quality nanomaterials with unique characteristics. Our study focuses on the biosynthesis of Cu-In-S (CIS) nanoparticles, which has garnered considerable attention in the past decade due to their low toxicity and versatile applications in biomedicine and solar cells. Despite this interest, there is a notable absence of reports on biological methods for CIS nanoparticle synthesis. In this research, three yeast species were isolated from soil samples in an extreme Antarctic environment-Union Glacier, Ellsworth Mountains. Among these isolates, Filobasidium stepposum demonstrated the capability to biosynthesize CIS nanoparticles when exposed to copper sulfate, indium chloride, glutathione, and cysteine. Subsequent purification and spectroscopic characterization confirmed the presence of characteristic absorbance and fluorescence peaks for CIS nanoparticles at 500 and 650 nm, respectively. Transmission electron microscopy analysis revealed the synthesis of monodisperse nanoparticles with a size range of 3-5 nm. Energy dispersive X-ray spectroscopy confirmed the composition of the nanoparticles, revealing the presence of copper, indium, and sulfur. The copper/indium ratio ranged from 0.15 to 0.27, depending on the reaction time. The biosynthesized CIS nanoparticles showed higher photostability than biomimetic nanoparticles and demonstrated successful application as photosensitizers in quantum dot-sensitized solar cells (QDSSC), achieving a conversion efficiency of up to 0.0247%. In summary, this work presents a cost-effective, straightforward, and environmentally friendly method for CIS nanoparticle synthesis. Furthermore, it constitutes the first documented instance of a biological procedure for producing these nanoparticles, opening avenues for the development of environmentally sustainable solar cells.