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.

Potential for resistance to freezing by non-virulent bacteria isolated from Antarctica.

Industrial sectors are searching for new compounds to improve the preservation of food and blood, human tissues, and fuels used at low temperatures. Antarctic microorganisms have mechanisms to overcome injuries caused by low temperatures, making them sources of compounds with antifreeze activity. However, it is mandatory that such compounds do not pose a risk to human health. The present study evaluated the potential of Antarctic bacteria to resist freezing, produce virulence factors, their tolerance to physiological pHs/temperature and resistance to antibiotics. Sixty-five isolates were tested for antifreeze compound production, among which, 31 grew after the test. Of these, 3 strains of Arthrobacter sp. (356, 358 and 443), one Psychromonas arctica (ESH238) and one unidentified strain (363) showed positive results for hemolytic activity. Psychrobacter sp. 456 showed proteinase activity. None of the isolates showed resistance to the antibiotics. All isolates were able to grow in one of the three pHs (4, 7 and 8) and/or temperature (36, 38 and 40 ºC). Antarctic bacterial present potential for the production of antifreeze compounds and may be considered safe in industrial processes. The characterization of the genes responsible for virulence factors should be carried out to reinforce the potential applicability of such bacteria.

Heavy metal resistance genes and plasmid-mediated quinolone resistance genes in Arthrobacter sp. isolated from Brazilian soils.

Arthrobacter sp. are Gram-positive bacilli commonly obtained from soil and in the hospital environment. These species have been reported to cause several types of infection. Heavy metals are a threat to the ecological system due to their high-levels of toxicity and the fluoroquinolones are antimicrobials widely used for the treatment of different bacterial infections. The aim of this study was to investigate the resistance to fluoroquinolone and heavy metals, the presence of plasmid-mediated resistance (PMQR) genes and heavy metals resistance (HMR) genes and the presence of plasmids in Arthrobacter sp. obtained from Brazilian soils. Bacterial isolation was performed using soil samples from different Brazilian regions. The bacterial identification was performed by 16S rRNA gene sequencing. The resistance profile for fluoroquinolones and heavy metals was determined by MIC. Several PMQR and HMR genes and plasmid families were investigated by PCR. Eight isolates were obtained from soil samples from different cultivations and regions of Brazil. All isolates were resistant to all fluoroquinolones, cadmium, cobalt and zinc and the majority to copper. Among the PMQR genes, the qepA (4) was the most prevalent, followed by qnrS (3), qnrB (3), oqxB (2) and oqxA (1). Among the HMR genes, the copA was detected in all isolates and the czcA in two isolates. The replication origin of the ColE-like plasmid was detected in all isolates; however, no plasmid was detected by extraction. The association of resistance to heavy metals and antimicrobials is a threat to the environmental balance and to human health. There are no studies reporting the association of PMQR and HMR genes in bacteria belonging to the genus Arthrobacter. To the best of our knowledge, this is the first report of qnrB, qepA, oqxA and oqxB in Arthrobacter species.

[The plant growth-promoting rhizobacterium Arthrobacter agilis UMCV2 endophytically colonizes Medicago truncatula]. / La rizobacteria promotora del crecimiento vegetal Arthrobacter agilis UMCV2 coloniza endofíticamente a Medicago truncatula.

Arthrobacter agilis UMCV2 is a rhizosphere bacterium that promotes legume growth by solubilization of iron, which is supplied to the plant. A second growth promotion mechanism produces volatile compounds that stimulate iron uptake activities. Additionally, A. agilis UMCV2 is capable of inhibiting the growth of phytopathogens. A combination of quantitative polymerase chain reaction and fluorescence in situ hybridization techniques were used here to detect and quantify the presence of the bacterium in the internal tissues of the legume Medicago truncatula. Our results demonstrate that A. agilis UMCV2 behaves as an endophytic bacterium of M. truncatula, particularly in environments where iron is available.

Microbial Community Profile and Water Quality in a Protected Area of the Caatinga Biome.

The Caatinga is a semi-arid biome in northeast Brazil. The Paraguaçú River is located in the Caatinga biome, and part of its course is protected by the National Park of Chapada Diamantina (PNCD). In this study we evaluated the effect of PNCD protection on the water quality and microbial community diversity of this river by analyzing water samples obtained from points located inside and outside the PNCD in both wet and dry seasons. Results of water quality analysis showed higher levels of silicate, ammonia, particulate organic carbon, and nitrite in samples from the unprotected area compared with those from protected areas. Pyrosequencing of the 16S rRNA genes revealed that Burkholderiales was abundant in samples from all three sites during both seasons and was represented primarily by the genus Polynucleobacter and members of the Comamonadaceae family (e.g., genus Limnohabitans). During the dry season, the unprotected area showed a higher abundance of Flavobacterium sp. and Arthrobacter sp., which are frequently associated with the presence and/or degradation of arsenic and pesticide compounds. In addition, genes that appear to be related to agricultural impacts on the environment, as well as those involved in arsenic and cadmium resistance, copper homeostasis, and propanediol utilization, were detected in the unprotected areas by metagenomic sequencing. Although PNCD protection improves water quality, agricultural activities around the park may affect water quality within the park and may account for the presence of bacteria capable of pesticide degradation and assimilation, evidencing possible anthropogenic impacts on the Caatinga.

Tutorial for writing systematic reviews for the Brazilian Journal of Physical Therapy (BJPT) / Tutorial para elaboração de revisões sistemáticas para o Brazilian Journal of Physical Therapy (BJPT)

Systematic reviews aim to summarize all evidence using very rigorous methods in order to address a specific research question with less bias as possible. Systematic reviews are widely used in the field of physical therapy, however not all reviews have good quality. This tutorial aims to guide authors of the Brazilian Journal of Physical Therapy on how systematic reviews should be conducted and reported in order to be accepted for publication. It is expected that this tutorial will help authors of systematic reviews as well as journal editors and reviewers on how to conduct, report, critically appraise and interpret this type of study design. .

Revisões sistemáticas têm como objetivo sumarizar toda a evidência disponível, através de métodos rigorosos, para responder a uma pergunta de pesquisa específica com o mínimo de viés possível. Revisões sistemáticas são amplamente utilizadas na fisioterapia, porém nem todas as revisões possuem boa qualidade. Esse tutorial tem como objetivo guiar os autores do Brazilian Journal of Physical Therapy sobre como revisões sistemáticas deveriam ser conduzidas e descritas para que sejam aceitas para publicação. Espera-se que esse tutorial irá auxiliar autores de revisões sistemáticas, assim como editores e revisores de periódicos em como conduzir, descrever, fazer análise crítica e interpretar esse tipo de delineamento de pesquisa.

Cloning and sequencing of a dextranase-encoding cDNA from Penicillium minioluteum.

A cDNA from Penicillium minioluteum HI-4 encoding a dextranase (1,6-alpha-glucan hydrolase, EC 3.2.1.11) was isolated and characterized. cDNA clones corresponding to genes expressed in dextran-induced cultures were identified by differential hybridization. Southern hybridization and restriction mapping analysis of selected clones revealed four different groups of cDNAs. The dextranase cDNA was identified after expressing a cDNA fragment from each of the isolated groups of cDNA clones in the Escherichia coli T7 system. The expression of a 2 kb cDNA fragment in E. coli led to the production of a 67 kDa protein which was recognized by an anti-dextranase polyclonal antibody. The cDNA contains 2109 bp plus a poly(A) tail, coding for a protein of 608 amino acids, including 20 N-terminal amino acid residues which might correspond to a signal peptide. There was 29% sequence identity between the P. minioluteum dextranase and the dextranase from Arthrobacter sp. CB-8.