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Item Antibacterial activity of the antarctic bacterium Janthinobacterium sp. SMN 33.6 against multi-resistant Gram-negative bacteria(Pontificia Universidad Católica de Valparaíso, 2014) Asencio, Geraldine; Lavin, Paris; Alegria, Karen; Domínguez, Mariana; Bello, Helia; González-Rocha, Gerardo; González-Aravena, MarceloBackground: The increment of resistant strains to commonly used antibiotics in clinical practices places in evidence the urgent need to search for newcompounds with antibacterial activity. The adaptations that Antarctic microorganisms have developed, due to the extreme environment that they inhabit, promote themas a potential new source of active compounds for the control of microorganisms causing infections associated with health care. The aimof this studywas to evaluate the antibacterial activity of an ethanol extract of the Antarctic bacterium Janthinobacterium sp., strain SMN 33.6, against nosocomial multi-resistant Gram-negative bacteria. Results: Inhibitory activity against human Gram-negative bacterial pathogens, with concentrations that varied between 0.5 and 16 μg ml-1, was demonstrated. Conclusions: The ethanolic extract of Janthinobacterium sp. SMN 33.6 possesses antibacterial activity against a chromosomal AmpC beta-lactamase-producing strain of Serratia marcescens, an extended-spectrum beta-lactamase-producing Escherichia coli and also against carbapenemase-producing strains of Acinetobacter baumannii and Pseudomonas aeruginosa. This becomes a potential and interesting biotechnological tool for the control of bacteria with multi-resistance to commonly used antibiotics.Item The importance of local settings: within-year variability in seawater temperature at south bay, western antarctic peninsula(Peerj Inc, 2018-01-18) Cárdenas, C.A; González-Aravena, Marcelo; Santibáñez, Pamela A.The Western Antarctic Peninsula (WAP) has undergone significant changes in air and seawater temperatures during the last 50 years. Although highly stenotherm Antarctic organisms are expected to be severely affected by the increase of seawater temperature, high-resolution datasets of seawater temperature within coastal areas of the WAP (where diverse marine communities have been reported) are not commonly available. Here we report on within-year (2016 2017) variation in seawater temperature at three sites on Doumer Island, Palmer Archipelago, WAP. Within a year, Antarctic organisms in South Bay were exposed to water temperatures in excess of 2 C for more than 25 days and 2.5 C for more than 10 days. We recorded a temperature range between����1.7 to 3.0 C. Warming of seawater temperature was 3.75 times faster after October 2016 than it was before October. Results from this study indicate that organisms at South Bay are already exposed to temperatures that are being used in experimental studies to evaluate physiological responses to thermal stress in WAP organisms. Continuous measurements of short to long-term variability in seawater temperature provides important information for parametrizing meaningful experimental treatments that aim to assess the local effects of environmental variation on Antarctic organisms under future climate scenarios.Item HSP70 from the Antarctic sea urchin Sterechinus neumayeri: molecular characterization and expression in response to heat stress(Sociedad de Biología de Chile, 2018) González-Aravena, Marcelo; Calfio, Camila; Mercado, Luis; Morales-Lange, Byron; Bethke, Jorn; De Lorgeril, Julien; Cárdenas, César A.Background: Heat stress proteins are implicated in stabilizing and refolding denatured proteins in vertebrates and invertebrates. Members of the Hsp70 gene family comprise the cognate heat shock protein (Hsc70) and inducible heat shock protein (Hsp70). However, the cDNA sequence and the expression of Hsp70 in the Antarctic sea urchin are unknown. Methods: We amplified and cloned a transcript sequence of 1991 bp from the Antarctic sea urchin Sterechinus neumayeri, experimentally exposed to heat stress (5 and 10 °C for 1, 24 and 48 h). RACE-PCR and qPCR were employed to determine Hsp70 gene expression, while western blot and ELISA methods were used to determine protein expression. Results: The sequence obtained from S. neumayeri showed high identity with Hsp70 members. Several Hsp70 family features were identified in the deduced amino acid sequence and they indicate that the isolated Hsp70 is related to the cognate heat shock protein type. The corresponding 70 kDa protein, called Sn-Hsp70, was immune detected in the coelomocytes and the digestive tract of S. neumayeri using a monospecific polyclonal antibody. We showed that S. neumayeri do not respond to acute heat stress by up-regulation of Sn-Hsp70 at transcript and protein level. Furthermore, the Sn-Hsp70 protein expression was not induced in the digestive tract. Conclusions: Our results provide the first molecular evidence that Sn-Hsp70 is expressed constitutively and is noninduced by heat stress in S. neumayeri.Item High similarity in the microbiota of cold- water sponges of the Genus Mycale from two different geographical areas(Peerj Inc, 2018-06-07) Cárdenas, César A.; González-Aravena, Marcelo; Font, Alejandro; Hestetun, Jon T.; Hajdu, Eduardo; Trefault, Nicole; Malmberg, Maja; Bongcam-Rudloff, ErikSponges belonging to genus Mycale are common and widely distributed across the oceans and represent a significant component of benthic communities in term of their biomass, which in many species is largely composed by bacteria. However, the microbial communities associated with Mycale species inhabiting different geographical areas have not been previously compared. Here, we provide the first detailed description of the microbiota of two Mycale species inhabiting the sub-Antarctic Magellan region (53 S) and the Western Antarctic Peninsula (62 64 S), two geographically distant areas (>1,300 km) with contrasting environmental conditions. The sponges Mycale (Aegogropila) magellanica and Mycale (Oxymycale) acerata are both abundant members of benthic communities in the Magellan region and in Antarctica, respectively. High throughput sequencing revealed a remarkable similarity in the microbiota of both sponge species, dominated by Proteobacteria and Bacteroidetes, with both species sharing more than 74% of the OTUs. In contrast, 16% and 10% of the OTUs were found only in either M. magellanica or M. acerata, respectively. Interestingly, despite slight differences in the relative abundance, the most dominant OTUs were present in both species, whereas the unique OTUs had very low abundances (less than 1% of the total abundance). These results show a significant overlap among the microbiota of both Mycale species and also suggest the existence of a low level of specificity of the most dominant symbiont groups.Item Expression pattern of heat shock proteins during acute thermal stress in the antarctic sea urchin, Sterechinus neumayeri(Sociedad de Biología de Chile, 2016) González, Karina; Gaitán-Espitia, Juan; Font, Alejandro; Cárdenas, César A.; González-Aravena, MarceloBackground: Antarctic marine organisms have evolved a variety of physiological, life-history and molecular adaptations that allow them to cope with the extreme conditions in one of the coldest and most temperaturestable marine environments on Earth. The increase in temperature of the Southern Ocean, product of climate change, represents a great challenge for the survival of these organisms. It has been documented that some Antarctic marine invertebrates are not capable of generating a thermal stress response by means of an increase in the synthesis of heat shock proteins, which could be related with their low capacity for acclimatization. In order to understand the role of heat shock proteins as a compensatory response in Antarctic marine species to projected scenarios of increased seawater temperatures, we assessed the expression of the genes Hsp90, Grp78, Hyou1 and Hsc70 in the Antarctic sea urchin Sterechinus neumayeri under three thermal treatments (1 °C, 3 °C and 5 °C), for a period of exposure of 1, 24 and 48 h. Results: The results obtained showed that these genes were expressed themselves in all of the tissues analyzed in a constitutive form. During acute thermal stress, an overexpression of the Hsp90, Grp78 and Hyou1 genes was observed in coelomocyte samples at 3 °C after 48 h, while in esophageal samples, an increase in Hsp90 and Grp78 expression was observed after 48 h. Thermal stress at 5 °C, in general, did not produce a significant increase in the expression of the genes that were studied. The expression of Hsp70 did not show modifications in its expression as a result of thermal stress. Conclusions: S. neumayeri is capable of overexpressing stress proteins as a result of thermal stress, however, this response is delayed and to a lesser degree compared to other Antarctic or temperate species. These results indicate that adult individuals could cope with the expected impacts caused by an increase in coastal sea temperatures in the Southern Ocean.Item Isolation and characterization of an antarctic flavobacterium strain with agarase and alginate lyase activities(De Gruyter Open, 2016) Lavin, Paris; Atala, Cristian; Gallardo-Cerda, Jorge; González-Aravena, Marcelo; De la Iglesia, Rodrigo; Oses, Rómulo; Torres-Díaz, Cristian; Trefault, Nicole; Molina-Montenegro, Marco A.; Laughinghouse IV, H. DailSeveral bacteria that are associated with macroalgae can use phycocolloids as a carbon source. Strain INACH002, isolated from decomposing Porphyra (Rhodophyta), in King George Island, Antarctica, was screened and characterized for the ability to produce agarase and alginate-lyase enzymatic activities. Our strain INACH002 was identified as a member of the genus Flavobacterium, closely related to Flavobacterium faecale, using 16S rRNA gene analysis. The INACH002 strain was characterized as psychrotrophic due to its optimal temperature (17 ºC) and maximum temperature (20°C) of growth. Agarase and alginate-lyase displayed enzymatic activities within a range of 10°C to 50°C, with differences in the optimal temperature to hydrolyze agar (50°C), agarose (50°C) and alginate (30°C) during the first 30 min of activity. Strain Flavobacterium INACH002 is a promising Antarctic biotechnological resource; however, further research is required to illustrate the structural and functional bases of the enzymatic performance observed during the degradation of different substrates at different temperatures.