Low levels of PAHs and organotin compounds in surface sediment samples from a broad marine area of 25 de Mayo (King George) Island, South Shetland Islands.

The Northern region of the Antarctic Peninsula constitutes the area with the highest human presence in West Antarctica. The human presence, with all the activities associated such as logistic, scientific and tourism operations, represents a potential risk of chemical pollution with both, organic and inorganic contaminants. Under these conditions knowledge about the presence and levels of the main persistent organic pollutants (POPs) is essential to evaluate the environmental status of this ecologically relevant and sensitive area. In this work, which complements our previous study regarding trace elements, we performed the first regional-scale monitoring of 24 PAHs (16 of them included in EPA list of primary pollutant), and organotin compounds (OTCs:TBT, DBT and MBT) in surface sediment from 68 sites comprising six different areas in Maxwell Bay, southeast coast of 25 de Mayo (King George) Island. POPs were quantified in surface sediment samples (20-30 m depth) obtained during two summer Antarctic expeditions by gas chromatography-mass spectrometry (GC-MS). The two most anthropized areas (South Fildes and Potter Cove) showed moderated evidence of pollution for PAHs and OTC. In some sampling sites the concentration of total PAHs was higher than 100 ng/g dw, while TBT was detected in only five samples, two of them located in Potter Cove (ranged between 14 and 18 ng/g dw), and three, located in South Fildes area (ranged between 118 and 416 ng/g dw). Although POPs contamination was evidenced in some samples close to scientific stations, a pollution pattern was not clearly identified.

Element concentrations of environmental concern in surface sediment samples from a broad marine area of 25 de Mayo (King George) Island, South Shetland Islands.

Western Antarctica (WA) constitutes the area with the highest human presence in the white continent and also the region where the effects of global warming are more evident worldwide. Such human presence represents a potential risk of pollution with both, organic and inorganic contaminants. Global warming also could modify dynamics and transport of the pollutants, increasing summer water runoff, ice melting and iceberg scouring. Under this fast-changing scenario, knowledge about the concentration of contaminants is essential to evaluate the environmental status of this ecologically relevant area. In this work, we performed the first regional-scale monitoring of 9 trace elements (Cr, Co, Ni, Cu, Zn, As, Pb, Cd and Hg), as well as Fe and Mn, in surface sediment from 64 sites comprising six different areas in Maxwell Bay, 25 de Mayo (King George) Island. Target elements were quantified in surface sediment samples (20-30 m depth) obtained during two summer Antarctic expeditions: 2010/11 and 2011/12 by inductively coupled plasma linked to a quadrupole mass spectrometer (ICP-MS). Based on the average values observed for the reference areas, baseline values were defined for the studied region. A regional enrichment in Cu (compared with the global mean upper crust) was observed and related to the widespread mineralization of volcanic rocks. The most anthropized area (South Fildes) mainly showed sediment class 3 (moderately polluted) for Pb, Cd and Hg with a number samples revealing some highly contaminated hot spots. Although elemental contamination in some samples close to scientific stations or sites where logistic operations were evidenced, a pollution pattern was not clearly identified. The present work represents the first regional-scale attempt to define the baseline values and the anthropic impacts in this region of the WA and also provides the first data about Hg concentration in surface sediment of the study area.

Contact dermatitis caused by dimethylfumarate in Argentina.

For the first time in Argentina, we describe an outbreak of contact dermatitis. New pairs of shoes caused intense pruritus, pain, and eruption, followed by edema, blisters, and a severe negative impact on the epidermal barrier of the feet. We identify dimethylfumarate as the causal agent and suggest an analytical method for its fast identification.

Influence of nutrients addition and bioaugmentation on the hydrocarbon biodegradation of a chronically contaminated Antarctic soil.

Complexity involved in the transport of soils and the restrictive legislation for the area makes on-site bioremediation the strategy of choice to reduce hydrocarbons contamination in Antarctica. The effect of biostimulation (with N and P) and bioaugmentation (with two bacterial consortia and a mix of bacterial strains) was analysed by using microcosms set up on metal trays containing 2.5 kg of contaminated soil from Marambio Station. At the end of the assay (45 days), all biostimulated systems showed significant increases in total heterotrophic aerobic and hydrocarbon-degrading bacterial counts. However, no differences were detected between bioaugmented and nonbioaugmented systems, except for J13 system which seemed to exert a negative effect on the natural bacterial flora. Hydrocarbons removal efficiencies agreed with changes in bacterial counts reaching 86 and 81% in M10 (bioaugmented) and CC (biostimulated only) systems. Results confirmed the feasibility of the application of bioremediation strategies to reduce hydrocarbon contamination in Antarctic soils and showed that, when soils are chronically contaminated, biostimulation is the best option. Bioaugmentation with hydrocarbon-degrading bacteria at numbers comparable to the total heterotrophic aerobic counts showed by the natural microflora did not improve the process and showed that they would turn the procedure unnecessarily more complex.

Extracellular proteases from the Antarctic marine pseudoalteromonas sp. P96-47 strain.

The extracellular protease-production capacity of 33 bacterial isolates taken from marine biotopes in King George Island, Antarctica, was evaluated in liquid cultures. The P96-47 isolate was selected due to its high production capacity and was identified as Pseudoalteromonas sp. The optimal growth temperature was 20 degrees C and the optimal for protease production was 15 degrees C. Proteases were purified from culture supernatants, developing a multiple-band profile in zymograms. They were classified as neutral metalloproteases and worked optimally at 45 degrees C with an Eact of 47 kJ/mol. Their stability was higher at neutral pH, retaining more than 80% of activity at pH 6-10 after 3 h incubation at 4 degrees C. After 90 min incubation at 40 and 50 degrees C, the percentages of residual activities were 78% and 44%. These results contribute to the basic knowledge of Antarctic marine proteases and also help evaluate the probable industrial applications of P96-47 proteases.

Extracellular proteases from the Antarctic marine Pseudoalteromonas sp. P96-47 strain / Proteasas extracelulares de la cepa marina antártica Pseudoalteromonas sp. P96-47

The extracellular protease-production capacity of 33 bacterial isolates taken from marine biotopes in King George Island, Antarctica, was evaluated in liquid cultures. The P96-47 isolate was selected due to its high production capacity and was identified as Pseudoalteromonas sp. The optimal growth temperature was 20 °C and the optimal for protease production was 15 °C. Proteases were purified from culture supernatants, developing a multiple-band profile in zymograms. They were classified as neutral metalloproteases and worked optimally at 45 °C with an Eact of 47 kJ/ mol. Their stability was higher at neutral pH, retaining more than 80% of activity at pH 6-10 after 3 h incubation at 4 °C. After 90 min incubation at 40 and 50 °C, the percentages of residual activities were 78% and 44%. These results contribute to the basic knowledge of Antarctic marine proteases and also help evaluate the probable industrial applications of P96-47 proteases.

La capacidad productora de proteasas extracelulares de 33 aislamientos bacterianos tomados de biotopos marinos en la Isla Rey Jorge, Antártida, fue evaluada en cultivo líquido. El aislamiento P96-47 fue seleccionado debido a su alta capacidad productora y fue identificado como Pseudoalteromonas sp. La temperatura óptima de crecimiento fue de 20 °C y la de producción de 15 °C. Las proteasas fueron purificadas a partir del sobrenadante de cultivo, y en los zimogramas desarrollaron un perfil de múltiples bandas. Estas proteasas fueron clasificadas como metaloproteasas neutras y se observó que trabajan óptimamente a 45 °C, con una Eact de 47 kJ/ mol. Su estabilidad fue superior a pH neutro y retuvieron más del 80% de su actividad a pH 6-10 después de 3 h de incubación a 4 °C. Luego de 90 min de incubación a 40 y 50 °C, las actividades residuales fueron 78% y 44%, respectivamente. Los resultados que se presentan en este trabajo contribuyen al conocimiento básico de las proteasas marinas antárticas y también a evaluar las probables aplicaciones industriales de las proteasas de P96-47.

[Changes in viability of two Antarctic marine bacteria exposed to solar radiation in the water column: influence of vertical mixing]. / Cambios en la viabilidad de dos bacterias marinas antárticas expuestas a la radiación solar en la columna de agua: influencia de la mezcla vertical.

The effect of UV radiation on two Antarctic marine bacterial strains (UVps and UVvi) was studied in the water column of Potter Cove (South Shetland, Antarctica). Quartz flasks were filled with the bacterial suspensions and exposed to solar radiation at 0 m, 1 m and 3 m depth. Assays using flasks exposed to direct solar radiation and others using flasks covered with/by interferential filters which discriminate between UVA and UVB, were performed. In other assays, a vertical mixing of 4 m/h was simulated. Both strains showed a significant decrease in viability (expressed as colony - forming units) when exposed to a surface UVB dose of 8.4 kJ m(-2). Studies with interferential filters showed a significant decrease at 0 and 1 m depth under both UV treatments. The UVps strain appeared to be more sensitive to UVB than to UVA. Damage produced by UVB was attenuated by the vertical mixing when the surface UVB dose was 4.8 kJ m(-2). This effect was not observed when surface UVB dose was 7.7 kJ m(-2). These results show that the negative effect caused by UVB radiation on the bacterioplankton would be significant only in the first meter of water column of the Antarctic coastal waters with high levels of suspended particulate material.

Cambios en la viabilidad de dos bacterias marinas antárticas expuestas a la radiación solar en la columna de agua: influencia de la mezcla vertical / Changes in viability of two Antarctic marine bacteria exposed to solar radiation in the water column: influence of vertical mixing

Se estudió el efecto de la radiación ultravioleta (RUV) sobre dos cepas bacterianas marinas antárticas (UVps y UVvi) en la columna de agua de la caleta Potter (Shetland del Sur, Antártida). Frascos de cuarzo con las cepas en estudio fueron expuestos a la radiación solar en superficie, a 1 m y a 3 m de profundidad. Se realizaron ensayos con exposición directa y con filtros interferenciales que discriminaron la radiación UVA y la UVB. En otros ensayos se simuló una mezcla vertical de 4 m/h. Ambas cepas mostraron una disminución significativa del número de unidades formadoras de colonias, tanto en superficie como a 1 m de profundidad, luego de exponerlas a dosis superficiales de UVB de 8,4 kJ m-2. El estudio con filtros interferenciales mostró una disminución significativa de la viabilidad en ambos tratamientos UV en superficie y a 1 m. La cepa UVps mostró mayor sensibilidad a la UVB que a la UVA. La mezcla vertical amortiguó el daño causado por la UVB cuando la dosis en superficie fue de 4,8 kJ m-2. Este efecto amortiguador no se observó cuando la dosis en superficie fue de 7,7 kJ m-2. Estos resultados muestran que el efecto negativo de la RUV sobre el bacterioplancton sería particularmente importante en el primer metro de profundidad de las aguas costeras antárticas con abundante material particulado en suspensión.

The effect of UV radiation on two Antarctic marine bacterial strains (UVps and UVvi) was studied in the water column of Potter Cove (South Shetland, Antarctica). Quartz flasks were filled with the bacterial suspensions and exposed to solar radiation at 0 m, 1 m and 3 m depth. Assays using flasks exposed to direct solar radiation and others using flasks covered with/by interferential filters which discriminate between UVA and UVB, were performed. In other assays, a vertical mixing of 4 m/h was simulated. Both strains showed a significant decrease in viability (expressed as colony - forming units) when exposed to a surface UVB dose of 8.4 kJ m-2. Studies with interferential filters showed a significant decrease at 0 and 1 m depth under both UV treatments. The UVps strain appeared to be more sensitive to UVB than to UVA. Damage produced by UVB was attenuated by the vertical mixing when the surface UVB dose was 4.8 kJ m-2. This effect was not observed when surface UVB dose was 7.7 kJ m-2. These results show that the negative effect caused by UVB radiation on the bacterioplankton would be significant only in the first meter of water column of the Antarctic coastal waters with high levels of suspended particulate material.

Factors influencing protease production by two Antarctic strains of Stenotrophomonas maltophilia.

The influence of culture medium buffer capacity, the supplementation of culture medium with L-ala and the requirement of calcium for exoprotease production by Antarctic psychrotrophic Stenotrophomonas maltophilia strains ANT-1-1 and ANT-7-1 were examined. When increasing concentrations of calcium chloride (0 to 0.3 g l-1) were added to culture media, maximum protease production yields increased 70-75% (ANT-1-1) and 50% (ANT-7-1), while biomass levels showed little difference. Calcium was also necessary for optimal activity of proteases. L-ala had no effect on protease production. The reduction in buffer capacity, with the consequent change in external pH, had a positive effect, enhancing protease yields. Secretion of proteases into the medium started at the beginning of the stationary phase, corresponding with a rise in pH values up to pH 8.7 and was maximal at 36 h of culture. These results indicate that the regulation of calcium concentration and buffer capacity and also pH monitoring are factors to be considered when the design of an industrial culture medium and the optimisation of protease production processes using these Antarctic strains are concerned.

Factors influencing protease production by two Antarctic strains of Stenotrophomonas maltophilia

The influence of culture medium buffer capacity, the supplementation of culture medium with L-ala and the requirement of calcium for exoprotease production by Antarctic psychrotrophic Stenotrophomonas maltophilia strains ANT-1-1 and ANT-7-1 were examined. When increasing concentrations of calcium chloride (0 to 0.3 g l-1) were added to culture media, maximum protease production yields increased 70-75 (ANT-1-1) and 50 (ANT-7-1), while biomass levels showed little difference. Calcium was also necessary for optimal activity of proteases. L-ala had no effect on protease production. The reduction in buffer capacity, with the consequent change in external pH, had a positive effect, enhancing protease yields. Secretion of proteases into the medium started at the beginning of the stationary phase, corresponding with a rise in pH values up to pH 8.7 and was maximal at 36 h of culture. These results indicate that the regulation of calcium concentration and buffer capacity and also pH monitoring are factors to be considered when the design of an industrial culture medium and the optimisation of protease production processes using these Antarctic strains are concerned.

Factors influencing protease production by two Antarctic strains of Stenotrophomonas maltophilia

The influence of culture medium buffer capacity, the supplementation of culture medium with L-ala and the requirement of calcium for exoprotease production by Antarctic psychrotrophic Stenotrophomonas maltophilia strains ANT-1-1 and ANT-7-1 were examined. When increasing concentrations of calcium chloride (0 to 0.3 g l-1) were added to culture media, maximum protease production yields increased 70-75 (ANT-1-1) and 50 (ANT-7-1), while biomass levels showed little difference. Calcium was also necessary for optimal activity of proteases. L-ala had no effect on protease production. The reduction in buffer capacity, with the consequent change in external pH, had a positive effect, enhancing protease yields. Secretion of proteases into the medium started at the beginning of the stationary phase, corresponding with a rise in pH values up to pH 8.7 and was maximal at 36 h of culture. These results indicate that the regulation of calcium concentration and buffer capacity and also pH monitoring are factors to be considered when the design of an industrial culture medium and the optimisation of protease production processes using these Antarctic strains are concerned.(AU)

Factors influencing protease production by two Antarctic strains of Stenotrophomonas maltophilia.

The influence of culture medium buffer capacity, the supplementation of culture medium with L-ala and the requirement of calcium for exoprotease production by Antarctic psychrotrophic Stenotrophomonas maltophilia strains ANT-1-1 and ANT-7-1 were examined. When increasing concentrations of calcium chloride (0 to 0.3 g l-1) were added to culture media, maximum protease production yields increased 70-75

(ANT-1-1) and 50

(ANT-7-1), while biomass levels showed little difference. Calcium was also necessary for optimal activity of proteases. L-ala had no effect on protease production. The reduction in buffer capacity, with the consequent change in external pH, had a positive effect, enhancing protease yields. Secretion of proteases into the medium started at the beginning of the stationary phase, corresponding with a rise in pH values up to pH 8.7 and was maximal at 36 h of culture. These results indicate that the regulation of calcium concentration and buffer capacity and also pH monitoring are factors to be considered when the design of an industrial culture medium and the optimisation of protease production processes using these Antarctic strains are concerned.