Browsing by Author "Tamayo-Leiva, Javier"

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    Dark Diazotrophy during the Late Summer in Surface Waters of Chile Bay, West Antarctic Peninsula
    (2022) Alcaman-Arias, Maria E.; Cifuentes-Anticevic, Jeronimo; Castillo-Inaipil, Wilson; Farias, Laura; Sanhueza, Cynthia; Fernandez-Gomez, Beatriz; Verdugo, Josefa; Abarzua, Leslie; Ridley, Christina; Tamayo-Leiva, Javier; Diez, Beatriz
    Although crucial for the addition of new nitrogen in marine ecosystems, dinitrogen (N-2) fixation remains an understudied process, especially under dark conditions and in polar coastal areas, such as the West Antarctic Peninsula (WAP). New measurements of light and dark N-2 fixation rates in parallel with carbon (C) fixation rates, as well as analysis of the genetic marker nifH for diazotrophic organisms, were conducted during the late summer in the coastal waters of Chile Bay, South Shetland Islands, WAP. During six late summers (February 2013 to 2019), Chile Bay was characterized by high NO3- concentrations (similar to 20 mu M) and an NH4+ content that remained stable near 0.5 mu M. The N:P ratio was approximately 14.1, thus close to that of the Redfield ratio (16:1). The presence of Cluster I and Cluster III nifH gene sequences closely related to Alpha-, Delta- and, to a lesser extent, Gammaproteobacteria, suggests that chemosynthetic and heterotrophic bacteria are primarily responsible for N-2 fixation in the bay. Photosynthetic carbon assimilation ranged from 51.18 to 1471 nmol C L-1 d(-1), while dark chemosynthesis ranged from 9.24 to 805 nmol C L-1 d(-1). N2 fixation rates were higher under dark conditions (up to 45.40 nmol N L-1 d(-1)) than under light conditions (up to 7.70 nmol N L-1 d(-1)), possibly contributing more than 37% to new nitrogen-based production (>2.5 g N m(-2) y(-1)). Of all the environmental factors measured, only PO43--exhibited a significant correlation with C and N-2 rates, being negatively correlated (p < 0.05) with dark chemosynthesis and N-2 fixation under the light condition, revealing the importance of the N:P ratio for these processes in Chile Bay. This significant contribution of N-2 fixation expands the ubiquity and biological potential of these marine chemosynthetic diazotrophs. As such, this process should be considered along with the entire N cycle when further reviewing highly productive Antarctic coastal waters and the diazotrophic potential of the global marine ecosystem.
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    Diversity and functionality of soil prokaryotic communities in antarctic volcanic soils: insights from penguin-influenced environments
    (2024) Segura, Diego; Jordaan, Karen; Diez, Beatriz; Tamayo-Leiva, Javier; Doetterl, Sebastian; Wasner, Daniel; Cifuentes-Anticevic, Jeronimo; Casanova-Katny, Angelica
    In the nutrient-limited Antarctic terrestrial habitat, penguins transfer a significant amount of nutrients from the marine to the terrestrial ecosystem through their depositions (i.e., guano). This guano influences soil physicochemical properties, leading to the formation of ornithogenic soil rich in nutrients and organic matter. We hypothesize that soil prokaryotic communities will be strongly influenced by the contribution of nitrogenous nutrients from penguin rookeries, maintaining the influence over long distances. The objective was to establish how the soil prokaryotic diversity and community structure change with distance from a penguin colony, which provides large amounts of guano and nitrogenous compounds, and to study the effects of these nutrients on the functional role of these communities. Methods include volcanic soil sampling along a 1200 m transect from the penguin active rookery and the characterization of soil nutrient content and soil prokaryotic communities using 16S rRNA high-throughput amplicon sequencing. In contrast to our hypothesis, the results showed that the impact of guano from the penguin colony was restricted to the first 300 m. Probably because the penguin rookery was sheltered, strong wind and wind direction did not affect the transport of nutrients from the penguin rookery. Areas close to the penguin rookery were dominated by Proteobacteria and Bacteroidetes, while areas situated further away were dominated by Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Nitrospirae, and Planctomycetes. Beta diversity analysis among the soil prokaryotic communities revealed a high degree of community heterogeneity, strongly associated with N compound characteristics (NH4, NO3, and %N), C, and pH. Inferences from N metabolism genes suggest a high potential of the microbial community for dissimilatory nitrate reduction genes (DNRA) to ammonium, assimilatory nitrate reduction (ANR), and denitrification. Although it is assumed that the nitrogenous compounds of the penguin colonies reach long distances and affect the prokaryotic community, this effect can vary with wind directions or the morphology of the site, reducing the impact of the guano over long distances, as our results indicate. On the other hand, functional predictions give some clues about the main actors in nitrogen cycling, through processes like dissimilatory nitrate reduction, assimilatory nitrate reduction, and denitrification.
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    Global phylogenomic novelty of the Cas1 gene from hot spring microbial communities
    (2022) Salgado Salgado, Oscar; Guajardo-Leiva, Sergio; Moya-Beltrán, Ana; Barbosa, Carla; Ridley, Christina; Tamayo-Leiva, Javier; Quatrini, Raquel; Mojica, Francisco; Díez, Beatriz
    The Cas1 protein is essential for the functioning of CRISPR-Cas adaptive systems. However, despite the high prevalence of CRISPR-Cas systems in thermophilic microorganisms, few studies have investigated the occurrence and diversity of Cas1 across hot spring microbial communities. Phylogenomic analysis of 2,150 Cas1 sequences recovered from 48 metagenomes representing hot springs (42–80°C, pH 6–9) from three continents, revealed similar ecological diversity of Cas1 and 16S rRNA associated with geographic location. Furthermore, phylogenetic analysis of the Cas1 sequences exposed a broad taxonomic distribution in thermophilic bacteria, with new clades of Cas1 homologs branching at the root of the tree or at the root of known clades harboring reference Cas1 types. Additionally, a new family of casposases was identified from hot springs, which further completes the evolutionary landscape of the Cas1 superfamily. This ecological study contributes new Cas1 sequences from known and novel locations worldwide, mainly focusing on under-sampled hot spring microbial mat taxa. Results herein show that circumneutral hot springs are environments harboring high diversity and novelty related to adaptive immunity systems.
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    Influence of Estuarine Water on the Microbial Community Structure of Patagonian Fjords
    (2021) Tamayo-Leiva, Javier; Cifuentes-Anticevic, Jeronimo; Aparicio-Rizzo, Pilar; Arroyo, Jose Ignacio; Masotti, Italo; Diez, Beatriz
    Fjords are sensitive areas affected by climate change and can act as a natural laboratory to study microbial ecological processes. The Chilean Patagonian fjords (41-56 degrees S), belonging to the Subantarctic ecosystem (46-60 degrees S), make up one of the world's largest fjord systems. In this region, Estuarine Water (EW) strongly influences oceanographic conditions, generating sharp gradients of oxygen, salinity and nutrients, the effects of which on the microbial community structure are poorly understood. During the spring of 2017 we studied the ecological patterns (dispersal and oceanographic factors) underlying the microbial community distribution in a linear span of 450 km along the estuarine-influenced Chilean Patagonian fjords. Our results show that widespread microbial dispersion existed along the fjords where bacterioplankton exhibited dependence on the eukaryotic phytoplankton community composition. This dependence was particularly observed under the low chlorophyll-a conditions of the Baker Channel area, in which a significant relationship was revealed between SAR11 Clade III and the eukaryotic families Pyrenomonadaceae (Cryptophyte) and Coccomyxaceae (Chlorophyta). Furthermore, dissolved oxygen and salinity were revealed as the main drivers influencing the surface marine microbial communities in these fjords. A strong salinity gradient resulted in the segregation of the Baker Channel prokaryotic communities from the rest of the Patagonian fjords. Likewise, Microbacteriaceae, Burkholderiaceae and SAR11 Clade III, commonly found in freshwater, were strongly associated with EW conditions in these fjords. The direct effect of EW on the microbial community structure and diversity of the fjords exemplifies the significance that climate change and, in particular, deglaciation have on this marine region and its productivity.
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    Proteorhodopsin Phototrophy in Antarctic Coastal Waters
    (2021) Cifuentes-Anticevic, Jeronimo; Alcaman-Arias, Maria E.; Alarcon-Schumacher, Tomas; Tamayo-Leiva, Javier; Pedros-Alio, Carlos; Farias, Laura; Diez, Beatriz
    Microbial proton-pumping rhodopsins are considered the simplest strategy among phototrophs to conserve energy from light. Proteorhodopsins are the most studied rhodopsins thus far because of their ubiquitous presence in the ocean, except in Antarctica, where they remain understudied. We analyzed proteorhodopsin abundance and transcriptional activity in the Western Antarctic coastal seawaters. Combining quantitative PCR (qPCR) and metagenomics, the relative abundance of proteorhodopsin-bearing bacteria accounted on average for 17, 3.5, and 29.7% of the bacterial community in Chile Bay (South Shetland Islands) during 2014, 2016, and 2017 summer-autumn, respectively. The abundance of proteorhodopsin-bearing bacteria changed in relation to environmental conditions such as chlorophyll a and temperature. Alphaproteobacteria, Gammaproteobacteria, and Flavobacteriia were the main bacteria that transcribed the proteorhodopsin gene during day and night. Although green light-absorbing proteorhodopsin genes were more abundant than blue-absorbing ones, the latter were transcribed more intensely, resulting in .50% of the proteorhodopsin transcripts during the day and night. Flavobacteriia were the most abundant proteorhodopsin-bearing bacteria in the metagenomes; however, Alphaproteobacteria and Gammaproteobacteria were more represented in the metatranscriptomes, with qPCR quantification suggesting the dominance of the active SAR11 clade. Our results show that proteorhodopsin-bearing bacteria are prevalent in Antarctic coastal waters in late austral summer and early autumn, and their ecological relevance needs to be elucidated to better understand how sunlight energy is used in this marine ecosystem.