Browsing by Author "De la Iglesia, Rodrigo"

Now showing 1 - 6 of 6
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    Annual phytoplankton dynamics in coastal waters from Fildes Bay, Western Antarctic Peninsula
    (2021) Trefault, Nicole; De la Iglesia, Rodrigo; Moreno-Pino, Mario; dos Santos, Adriana Lopes; Ribeiro, Catherine Gerikas; Parada-Pozo, Genesis; Cristi, Antonia; Marie, Dominique; Vaulot, Daniel
    Year-round reports of phytoplankton dynamics in the West Antarctic Peninsula are rare and mainly limited to microscopy and/or pigment-based studies. We analyzed the phytoplankton community from coastal waters of Fildes Bay in the West Antarctic Peninsula between January 2014 and 2015 using metabarcoding of the nuclear and plastidial 18/16S rRNA gene from both size-fractionated and flow cytometry sorted samples. Overall 14 classes of photosynthetic eukaryotes were present in our samples with the following dominating: Bacillariophyta (diatoms), Pelagophyceae and Dictyochophyceae for division Ochrophyta, Mamiellophyceae and Pyramimonadophyceae for division Chlorophyta, Haptophyta and Cryptophyta. Each metabarcoding approach yielded a different image of the phytoplankton community with for example Prymnesiophyceae more prevalent in plastidial metabarcodes and Mamiellophyceae in nuclear ones. Diatoms were dominant in the larger size fractions and during summer, while Prymnesiophyceae and Cryptophyceae were dominant in colder seasons. Pelagophyceae were particularly abundant towards the end of autumn (May). In addition of Micromonas polaris and Micromonas sp. clade B3, both previously reported in Arctic waters, we detected a new Micromonas 18S rRNA sequence signature, close to, but clearly distinct from M. polaris, which potentially represents a new clade specific of the Antarctic. These results highlight the need for complementary strategies as well as the importance of year-round monitoring for a comprehensive description of phytoplankton communities in Antarctic coastal waters.
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    CHANGES IN BACTERIAL COMMUNITY STRUCTURE ASSOCIATED WITH COASTAL COPPER ENRICHMENT
    (SOC ENVIRONMENTAL TOXICOLOGY & CHEMISTRY-SETAC, 2008) Moran, Ana C.; Hengst, Martha B.; De la Iglesia, Rodrigo; Andrade, Santiago; Correa, Juan A.; Gonzalez, Bernardo
    Marine bacterial communities isolated from the water column, sediment, the rock surface, and the green seaweed Ulva compressa were studied in an intertidal ecosystem. The study area included a coastal zone chronically affected by copper mine waste disposals. Bacterial community composition was analyzed by terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes, and multivariate analyses of T-RFLP data sets were used for comparisons. Results showed that diversity and richness indexes were not able to detect differences among compartments. However, comparisons within the same compartment clearly showed that copper enrichment was associated with changes in the composition of the bacterial communities and revealed that the magnitude of the effect depends on the compartment being considered. In this context, communities from sediments appeared as the most affected by copper enrichment. The present study also demonstrated that intertidal bacterial communities were dominated by Gammaproteobacteria, Firmicutes, and Actinobacteria and the changes in these communities were mainly due to changes in their relative abundances.
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    Distinct oxygen environments shape picoeukaryote assemblages thriving oxygen minimum zone waters off central Chile
    (2020) De la Iglesia, Rodrigo; Echenique-Subiabre, Isidora; Rodriguez-Marconi, Susana; Pablo Espinoza, Juan; von Dassow, Peter; Ulloa, Osvaldo; Trefault, Nicole
    Oxygen minimum zones (OMZs) support ocean biogeochemical cycles of global importance. The OMZ off central Chile is characterized by seasonally variable oxygen concentrations due to upwelling events. Bacterial and archaeal communities from this area have been previously described; however, picoeukaryote communities remain largely unexplored. In order to improve our knowledge on picoeukaryote ecology and the effect of controlling factors on its community structure, environmental parameters and 18S rRNA metabarcoding analyses were performed in water samples collected at several depths at a time series station on the continental shelf in March, May and August. Our results showed that oxygen, nitrate, silicate and temperature are relevant factors shaping the picoeukaryote community structure. Overall, according to our sequence dataset, the OMZ was dominated by Dinophyceae members including marine parasitic dinoflagellates. Moreover, dysoxic and suboxic conditions were enriched by fungi and phagotrophic protists from Ustilaginomycetes, Bicoecea and Choanoflagellatea. The latter is particularly relevant in the understanding of metazoan evolution and the origins of multicellularity in low-oxygen environments. Picoeukaryote communities changed significantly over the 3 months sampled with variations in water column stratification, including the occurrence of a winter bloom of Mamiellales. Altogether, this study reveals a great diversity and dynamics of picoeukaryotes inhabiting a coastal OMZ.
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    Hidden interactions in the intertidal rocky shore: variation in pedal mucus microbiota among marine grazers that feed on epilithic biofilm communities
    (2022) Arboleda-Baena, Clara; Pareja, Claudia Belen; Pla, Isadora; Logares, Ramiro; De la Iglesia, Rodrigo; Navarrete, Sergio Andres
    In marine ecosystems, most invertebrates possess diverse microbiomes on their external surfaces, such as those found in the pedal mucus of grazing gastropods and chitons that aids displacement on different surfaces. The microbes are then transported around and placed in contact with free-living microbial communities of micro and other macro -organisms, potentially exchanging species and homogenizing microbial composition and structure among grazer hosts. Here, we characterize the microbiota of the pedal mucus of five distantly related mollusk grazers, quantify differences in microbial community structure, mucus protein and carbohydrate content, and, through a simple laboratory experiment, assess their effects on integrated measures of biofilm abundance. Over 665 Amplicon Sequence Variants (ASVs) were found across grazers, with significant differences in abundance and composition among grazer species and epilithic biofilms. The pulmonate limpet Siphonaria lessonii and the periwinkle Echinolittorina peruviana shared similar microbiota. The microbiota of the chiton Chiton granosus, keyhole limpet Fissurella crassa, and scurrinid limpet Scurria araucana differed markedly from one another, and form those of the pulmonate limpet and periwinkle. Flavobacteriaceae (Bacteroidia) and Colwelliaceae (Gammaproteobacteria) were the most common among microbial taxa. Microbial strict specialists were found in only one grazer species. The pedal mucus pH was similar among grazers, but carbohydrate and protein concentrations differed significantly. Yet, differences in mucus composition were not reflected in microbial community structure. Only the pedal mucus of F. crassa and S. lessonii negatively affected the abundance of photosynthetic microorganisms in the biofilm, demonstrating the specificity of the pedal mucus effects on biofilm communities. Thus, the pedal mucus microbiota are distinct among grazer hosts and can affect and interact non-trophically with the epilithic biofilms on which grazers feed, potentially leading to microbial community coalescence mediated by grazer movement. Further studies are needed to unravel the myriad of non-trophic interactions and their reciprocal impacts between macro-and microbial communities.
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    Marine biocorrosion inhibition of Pseudomonas sp. biofilms on 304 stainless steel coated with poly-6-aminoindole produced by two different electrochemical methods
    (2024) Castaneda, Erik; Castillo, Javiera; Pascual, Marta; Rubio, Francisca; Vargas, Ignacio; De la Iglesia, Rodrigo; Armijo, Francisco
    Forming a bacterial biofilm on a metallic surface could result in biocorrosion and biofouling development. New environmentally friendly coatings are required to protect infrastructure, especially in coastal and marine environments. This study aimed to evaluate the mitigation of biocorrosion produced by Pseudomonas sp. biofilms on AISI 304 stainless steel (SS304) coupons modified with poly-6-aminoindole (PAIn) using two electrochemical techniques: cyclic voltammetry (SS/6-PAIn CV) and chronoamperometry (SS/6-PAIn CA). Experimental trials were performed in two stages: (i) the settlement and colonization of bacteria (1 h of incubation) and (ii) biofilm development (7 days of incubation). Colonized surfaces were characterized by epifluorescence and field emission scanning electron microscopy. Biocorrosion mitigation was evaluated using linear resistance polarization, electrochemical impedance spectroscopy, and linear scanning voltammetry in simulated seawater at 20 degrees C. The results showed biofilm formation on SS304 and SS/6-PAIn CA, but in SS/6-PAIn CV, the coating considerably reduced biofilm formation, with alterations in the size and structural organization of the biofilm. The biofilm cover percentages were 31.63 %, 22.66 %, and 9.25 % for SS304, SS/6-PAIn CA, and SS/6-PAIn CV, respectively. Thus, SS/6-PAIn CV reduced biofilm growth by 70.76 % compared to bare SS after seven days of culture. Electrochemical parameters determined by LSV and EIS showed a significant improvement in charge transfer resistance and coating resistance for the SS/6-PAIn CV compared to the coating produced by chronoamperometry. Although both coatings protected the metallic surface, SS/6-PAIn CV presented the best protective properties, emerging as a promising alternative coating to mitigate the biocorrosion process of SS304 in a marine environment.
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    Vegetation drives the response of the active fraction of the rhizosphere microbial communities to soil warming in Antarctic vascular plants
    (2022) Parada-Pozo, Genesis; Bravo, Leon A.; Saez, Patricia L.; Cavieres, Lohengrin A.; Reyes-Diaz, Marjorie; Abades, Sebastian; Alfaro, Fernando D.; De la Iglesia, Rodrigo; Trefault, Nicole
    In the Antarctic Peninsula, increases in mean annual temperature are associated with the coverage and population density of the two Antarctic vascular plant species-Deschampsia antarctica and Colobanthus quitensis-potentially modifying critical soil processes. In this study, we characterized the diversity and community composition of active microorganisms inhabiting the vascular plant rhizosphere in two sites with contrasting vegetation cover in King George Island, Western Antarctic Peninsula. We assessed the interplay between soil physicochemical properties and microbial diversity and composition, evaluating the effect of an in situ experimental warming on the microbial communities of the rhizosphere from D. antarctica and C. quitensis. Bacteria and Eukarya showed different responses to warming in both sites, and the effect was more noticeable in microbial eukaryotes from the low vegetation site. Furthermore, important changes were found in the relative abundance of Tepidisphaerales (Bacteria) and Ciliophora (Eukarya) between warming and control treatments. Our results showed that rhizosphere eukaryal communities are more sensitive to in situ warming than bacterial communities. Overall, our results indicate that vegetation drives the response of the active fraction of the microbial communities from the rhizosphere of Antarctic vascular plants to soil warming.