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Biosurfactant-producing bacteria can be found in contaminated environments such as biopurification systems (BPS) for pesticide treatments. A total of 18 isolates were screened to determine their ability to produce extracellular biosurfactants, using olive oil as the main carbon source. Out of the eighteen isolates, two strains (C11 and C27) were selected for biosurfactant production. The emulsification activities of the C11 and C27 strains using sunflower oil was 58.4 and 53.7%, respectively, and 46.6 and 48.0% using olive oil. Using molecular techniques and MALDI-TOF, the strains were identified as

The extreme weather conditions in the Antarctic have exerted selective pressures favoring differential features in bacteria to survive this untapped environment (i.e., antibiotic molecules). Notably, higher chances of antibiotic discovery from extremophiles have been proposed recently. Although new organic and environmentally friendly sources for helping in the control of plant pathogenic fungi are necessary, the information about anti-phytopathogenic applications of extremophile microorganisms from untapped environments is limited. In this study, we determined the antifungal effect of actinobacterial strains isolated from Antarctic soils and sediments. Co-culture inhibition assays and Minimum Inhibitory Concentration (MIC) determination revealed that all Antarctic strains (x28) can inhibit the growth of at least one phytopathogenic fungi including Fusarium oxysporum, Rhizoctonia solani, Botrytis sp. and Phytophthora infestans. Additionally, new novel antagonistic relationships are reported. Our work establishes a precedent on Antarctic actinobacteria strains with the capacity to produce antifungal compounds, and its potential for developing new fungicides or biocontrol agents solving current agriculture problems. RESUMEN Las condiciones climáticas extremas en la Antártica han ejercido presiones selectivas en las bacterias, de forma que éstas poseen características diferenciales (ej. moléculas antibióticas) que les permiten sobrevivir a este entorno poco explorado. Recientemente se ha propuesto que pueden existir mayores posibilidades para el descubrimiento de antibióticos a partir de extremófilos. A pesar de que son necesarias nuevas fuentes orgánicas y amigables con el medio ambiente para controlar los hongos patógenos en plantas, la información sobre las aplicaciones anti-fitopatogénicas de microorganismos extremófilos, de ambientes poco explorados, es limitada. En este estudio, se determinó el efecto antifúngico de actinobacterias aisladas de suelos y sedimentos antárticos. Mediante ensayos de inhibición en co-cultivo y determinación de la concentración mínima inhibitoria (CIM) se reveló que todas las cepas antárticas (x28) tienen la capacidad de inhibir el crecimiento de al menos un hongo fitopatógeno, incluyendo Fusarium oxysporum, Rhizoctonia solani, Botrytis sp. y Phytophthora infestans. Adicionalmente, se reportan nuevas relaciones antagónicas. Nuestro trabajo establece un precedente sobre cepas de actinobacterias antárticas con capacidad para la producción de compuestos antifúngicos y su potencial para el desarrollo de nuevos fungicidas o agentes de control biológico con el fin de resolver problemas actuales de la agricultura.

This study aims to describe the antibacterial and cytotoxic properties of a nanocomposite composed of silver chloride and silver nanoparticles (AgCl/Ag) biogenically synthesized using Arthrobacter sp., a non-pathogenic Antarctic soil bacterium. Spherical nanoparticles (hydrodynamic size of 42 nm) coated with biomolecules derived from Arthrobacter sp. were obtained. The antibacterial activity of the nanocomposite was demonstrated against Gram-positive and Gram-negative bacterial strains, including the multidrug-resistant Pseudomonas aeruginosa KPC 37. Furthermore, the cytotoxicity of AgCl/Ag nanocomposite was evaluated against the non-tumoral (Vero) and tumoral (SW-1353) cell lines. The nanocomposite was not cytotoxic to the Vero cells at concentrations below 150 μg/mL, whereas at concentrations above 25 μg/mL, a significant cytotoxic effect was observed for the SW-1353 cells. Interestingly, at 150 μg/mL, the nanocomposite demonstrated a potent antibacterial activity for all bacterial strains evaluated. To the best of our knowledge, this is the first report describing the green synthesis of AgCl/Ag nanocomposite by the bacterium Arthrobacter sp. isolated from Antarctic soil. The obtained nanocomposite may find important biomedical applications, with potent antibacterial and antitumoral effects and low toxicity to healthy cells.

Antarctic have been suggested as an attractive source for antibiotics discovery and members of Streptomyces genus have historically been studied as natural producers of antimicrobial metabolites. Nonetheless, our knowledge on antibiotic-producing Streptomyces from Antarctic is very limited. In this study, the antimicrobial activity of organic extracts from Antarctic Streptomyces strains was evaluated by disk diffusion assays and minimum inhibitory concentration. The strain Streptomyces sp. So13.3 showed the greatest antibiotic activity (MIC = 15.6 μg/mL) against Gram-positive bacteria and growth reduction of Gram‒negative pathogens. The bioactive fraction in the crude extract was revealed by TLC‒bioautography at Rf = 0.78 with molecular weight between 148 and 624 m/z detected by LC-ESI-MS/MS. The strain So13.3 was taxonomically affiliated as Streptomyces fildesensis. Whole genome sequencing and analysis suggested a 9.47 Mb genome size with 42 predicted biosynthetic gene clusters (BGCs) and 56 putative clusters representing a 22% of total genome content. Interestingly, a large number of them (11 of 42 BGCs and 40 of 56 putative BGCs), did not show similarities with other known BGCs. Our results highlight the potential of the Antarctic Streptomyces strains as a promising source of novel antimicrobials, particularly the strain Streptomyces fildesensis So13.3, which first draft genome is reported in this work.

Biosurfactants, a wide group of compounds produced by different microorganisms, generally have less toxicity and are more biodegradable than synthetic surfactants. Biosurfactant-producing bacteria can be found in contaminated environments, such as soils receiving pesticide applications constantly, or in pesticides treatment systems where microorganisms are adapted to biodegrading pesticides. Five pesticide-tolerant bacteria previously isolated from a pesticide biopurification system were evaluated as biosurfactant-producers. Pseudomonas rhodesiae C4, Rhodococcus jialingiae C8 and Pseudomonas marginalis C9 strains were positive in qualitative tests. Biosurfactant production by these strains using Bushnell-Haas medium with olive oil at 2% (w/v) was evaluated as emulsification index, oil displacement, droplet collapse test and surface tension. After 144 h, these strains showed a similar emulsification index of >55%. The two Pseudomonas (C4 and C9) strains showed lower superficial tension compared with Rhodococcus strain (C8)—34.47, 37.44 and 47.55 mN/m for strains C4, C9 and C8, respectively. The chemical characterization of the biosurfactants revealed the presence of glycolipids in P. rhodesiae (C4) and glycopeptides in P. marginalis (C9). The degradation of chlorpyrifos increased from 39.2% to 51.6% when biosurfactants produced by P.rhodesiae (C4) were added (10%) with respect to the control. Therefore, biopurification systems are a relevant source of biosurfactant-producing bacteria with environmental biotechnology applications.

In this study, we selected and characterized different pesticide-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a pesticides mixture. The amplicon analysis of biomixture reported that the phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were predominant. Six strains grew in the presence of chlorpyrifos and iprodione. Biochemical characterization showed that all isolates were positive for esterase, acid phosphatase, among others, and they were identified as Pseudomonas, Rhodococcus and Achromobacter based on molecular and proteomic analysis. Bacterial growth decreased as both pesticide concentrations increased from 10 to 100 mg L-1 in liquid culture. The Achromobacter sp. strain C1 showed the best chlorpyrifos removal rate of 0.072-0.147 d-1 a half-life of 4.7-9.7 d and a maximum metabolite concentration of 2.10 mg L-1 at 120 h. On the other hand, Pseudomonas sp. strain C9 showed the highest iprodione removal rate of 0.100-0.193 d-1 a half-life of 4-7 d and maximum metabolite concentration of 0.95 mg L-1 at 48 h. The Achromobacter and Pseudomonas strains showed a good potential as chlorpyrifos and iprodione-degrading bacteria.

This study provides the basis for implementing a continuous treatment system for wastewater containing a pesticide mixture formed by atrazine, iprodione, and chlorpyrifos. Two fungal strains (Verticilium sp. H5 and Metacordyceps sp. H12) isolated from a biomixture of a biopurification system were able to remove different pesticide concentrations (10 to 50 mg L−1) efficiently from the liquid medium; however, the half-life of the pesticides was reduced and characterized by a T1/2 of 5.4 to 9.2 d for atrazine, 3.7 to 5.8 d for iprodione, and 2.6 to 2.9 d for chlorpyrifos using the fungal consortium. The immobilization of the fungal consortium in alginate bead was effective, with the highest pesticide removal observed using an inoculum concentration of 30% wv−1. The packed-bed reactor with the immobilized fungal consortium, which was operated in the continuous mode at different flow rates (30, 60, and 90 mL h−1), required approximately 10 d to achieve removal efficiency (atrazine: 59%; iprodione: 96%; chlorpyrifos: ~85%). The bioreactor was sensitive to flow rate fluctuations but was able to recover performance quickly. The pesticide metabolites hydroxyatrazine, 3,5-dichloroaniline, and 3,5,6-trichloro-2-pyridinol were produced, and a slight accumulation of 3,5,6-trichloro-2-pyridinol was observed. Nevertheless, reactor removal efficiency was maintained until the study ended (60 d).

The development of novel biological products, such as enzymes, dyes, antibiotics, and others with high potential use for biotechnological applications, continues to stimulate the search for microorganisms in extreme environments. In recent years, the study of Antarctic ecosystems and their microorganisms has received more attention because psychrophilic microorganisms—mainly bacteria and their enzymes—have assumed considerable importance for biotechnological applications. In this study, we characterized a collection of 30 culturable Actinobacteria isolated from the South Shetland Islands, Antarctica, in order to relate their distribution and ability to produce extracellular enzymes with their biotechnological potential. The isolates belonged to eight genus in the phylum Actinobacteria: Arthrobacter, Brevibacterium, Curtobacterium, Janibacter, Knoellia, Rhodococcus, Streptomyces and Thermoleophilum. The screening for biologically active products showed that all the evaluated strains produced at least one extracellular enzyme at 4 °C, with protease, gelatinase and cellulase enzymes being the most common. In conclusion, our data showed that various Antarctic ecosystems are good sources for isolating cultivable Actinobacteria. Furthermore, these bacteria provide high-quality biological material for screening cold-active enzymes that have potential biotechnological applications and economic benefits.

Intensive use of pesticides applied simultaneously in field to improve the effectiveness of pest control increase the environmental contamination, affecting the soil and water quality. Some of the commonly used pesticides are the insecticide chlorpyrifos and the fungicide iprodione; being thus critically essential to develop bioremediation methods to remove these contaminants by tolerant-bacteria. In this study we selected and characterized different pesticides-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a mixture of the pesticides chlorpyrifos and iprodione. Out of the 10 isolated bacterial colonies, only six strains presented adequate growth in presence of the both pesticides at 100 mg L-1. Biochemical and enzymatic characterization using API ZYM showed that all isolates (100%) were positive for esterase, leucine aminopeptidase, acid phosphatase, and naphthol-AS-BI-phosphohydrolase. According to the molecular level study of the 16S ribosomal gene and MALDI TOF/TOF MS, it was possible to determine that the isolated bacteria belong to the genera Pseudomonas, Rhodococcus and Achromobacter. Bacterial growth decreased proportionally (R2 > 0.96) as been as both pesticide concentrations increased from 10 to 100 mg L-1. Achromobacter sp. strain C1 showed the best chlorpyrifos removal (between 56–29%) after 120 h of incubation. On the other hand, the highest iprodione removal (between 91.2–98.9%) was observed for the Pseudomonas sp. strain C9, which was not detected after 48 h of incubation. According with their identification and ability to remove the contaminants, Achromobacter sp. strain C1 and Pseudomonas sp. strain C9 appear as promising microorganisms for their use in the treatment of matrices contaminated with chlorpyrifos, iprodione or their mixture. The results of this study will help to improve current technologies for the biodegradation of this commonly used insecticide and fungicide, in order to give a response to the problem of contamination by pesticides.

The present study aimed to identify novel microbial producers of bioemulsificant compounds from Antarctic soils. Fifty-nine microbial strains were isolated from five different locations at South Shetland Islands, Antarctica, and screened for biosurfactant production by β-hemolytic activity. Strain So 3.2 was determined as bioemulsifier-producer and identified by phenotypic and molecular characterization as Streptomyces luridus. Emulsification activity, oil displacement method and drop-collapsing test were performed to evaluate the biosurfactant activity with different oils and hydrocarbons using two different culture media (Luria Bertani and Bushnell Haas in the presence of different carbon sources: glucose, glycerol, olive oil and n-Hexadecane). Cell free supernatant of Bushnell Haas culture supplemented with n-Hexadecane showed the best results for all tests. Emulsification of hydrocarbons exceeded 60%, reaching up to 90% on oil with high API grade, while displacement tests ranged from 8 cm to 4 cm in diameter according the culture media and tested oils. Our results revealed that Streptomyces luridus So3.2 is able to produce bioemulsifiers capable of emulsifying hydrocarbons and oils, which could be used in different biotechnological applications, particularly for bioremediation of environments contaminated by oil leaks.

This work presents the insecticidal activity of known sesquiterpenes with eudesmane skeleton synthesized by the conventional Robinson annulations reaction using dihydrocarvone and ethylvinylketone. The insecticidal activity was assayed against Drosophila melanogaster.

Extracts from Calceolaria talcana exhibited strong bioinsecticidal effects against Drosophila melanogaster and Spodoptera frugiperda. The most active extract was ethyl acetate and its majority compound verbascoside. The highest lethal concentration to the larvae of S. frugiperda and D. melanogaster was 20.0 μg/ml of the ethyl acetate extract with 95.8% and 67.0% of mortality, respectively. Against D. melanogaster the ethyl acetate extract showed the highest activity with 75.05% of antifeedant index at 25 μg/ml, methanol extract instead showed 100% to 100 μg/ml. At very low concentrations ethyl acetate and methanol extracts induce antifeedant and insect growth regulatory activity showing selective effects as deterrent and on the sclerotization showing a pre-emergence effect on S. frugiperda. The results from these extracts were better than showed by methanol extracts from Cedrela salvadorensis, Myrtillocactus geometrizans and Yucca periculosa samples used as positive controls.

Extracts obtained from a common shrub that occurs as part of vegetative species growing on arid lands of North-Central Chile and adjacent central Argentina known as “piquilin” Condalia microphylla (Rhamnaceae) showed insect growth inhibitory activity against the fall armyworm Spodoptera frugiperda, yellow meal worm Tenebrio molitor and fruit fly Drosophila melanogaster larvae in artificial diet feeding assays. The effects of these extracts on mortality, antifeedancy and growth inhibition were examined. The phytochemical profile of the most active extract was examined with conventional chromatographic and spectroscopic procedures. This n-hexane extract showed a high percentage of hentriacontane and triacontane. The observed mortality strongly correlates with the contents of these long-chain n-alkanes compounds, the LD50 for n-hexane, ethyl acetate and methanol extracts against S. frugiperda, were 3.89, 9.4, and 9.7 ppm; against T. molitor 5.2, 14.2, and 20.4 ppm, and against D. melanogaster 3.23, 7.65 and 17.9 ppm, respectively. Fil: Cespedes, Carlos L.. Universidad del Bio Bio; Chile Fil: Molina, Sofia C.. Universidad del Bio Bio; Chile Fil: Muñoz, Evelyn. Universidad del Bio Bio; Chile Fil: Lamilla, Claudio. Universidad del Bio Bio; Chile Fil: Alarcon, Julio. Universidad del Bio Bio; Chile Fil: Palacios, Sara Maria. Universidad Catolica de Córdoba. Facultad de Ciencias Químicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Carpinella, Maria Cecilia. Universidad Catolica de Córdoba. Facultad de Ciencias Químicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Avila, José G.. Universidad Nacional Autonoma de Mexico. Facultad de Estudios Superiores de Iztacala; México

The genus Blechnum has 13 species that are common plants, well-distributed in Chile. Here, we report a phytochemical analysis of B. chilense (Kaulf.) Mett., as well as the insecticidal effects of extracts of this plant. From the n-hexane fraction four phytoecdysones were isolated: ecdysone, ponasterone, shidasterone and 2-deoxycrustecdysone. A bioassay with Drosophila melanogaster larvae was used to evaluate insecticidal activity. The EtOAc and n-hexane fractions at 800 ppm caused 66.7 and 50.0% larval mortality, respectively. Treatments with both extracts at 800 ppm caused the greatest larval mortality, whereas treatments with 500 and 200 ppm induced premature pupation compared with the control and the highest adult mortality, probably due to interference with ecdysteroid metabolism and inhibition of ecdysis triggering hormone (ETH). The dead adult flies exhibited malformations.

The genus Blechnum has 13 species that are common plants, well-distributed in Chile. Here, we report a phytochemical analysis of B. chilense (Kaulf.) Mett., as well as the insecticidal effects of extracts of this plant. From the n-hexane fraction four phytoecdysones were isolated: ecdysone, ponasterone, shidasterone and 2-deoxycrustecdysone. A bioassay with Drosophila melanogaster larvae was used to evaluate insecticidal activity. The EtOAc and n-hexane fractions at 800 ppm caused 66.7 and 50.0% larval mortality, respectively. Treatments with both extracts at 800 ppm caused the greatest larval mortality, whereas treatments with 500 and 200 ppm induced premature pupation compared with the control and the highest adult mortality, probably due to interference with ecdysteroid metabolism and inhibition of ecdysis triggering hormone (ETH). The dead adult flies exhibited malformations.