Dissolved inorganic carbon fixation of Thaumarchaeota vs. Bacteria in the meso- and upper bathypelagic waters of the world’s oceans differentiated with the use of metabolic inhibitors

Recent studies suggest that the dark ocean prokaryotes fix inorganic carbon at rates substantially higher than assumed. We have studied the contribution of Archaea vs. Bacteria to total prokaryotic fixation of dissolved inorganic carbon (DIC) in the meso- and upper bathypelagic waters of the world’s oceans during the Malaspina circumnavigation expedition carried out between December 2010 and July 2011. We used the metabolic inhibitor Erythromycin, an antibiotic specifically inhibiting growth of Bacteria but not affecting Archaea. Bacteria dominated throughout the water column in the three major ocean basins (54% of the total DAPI counts), decreasing in their relative contribution to total prokaryotic abundance from the surface to the meso- and bathypelagic waters. By contrast, the relative contribution of Thaumarchaeota was generally higher in the meso- and bathypelagic layers than in the surface waters (up to 29% of the total DAPI counts in the Pacific Ocean). Averaged over the entire water column, Thaumarchaeota contributed 8%, 33% and 18% to the total prokaryotic DIC fixation in the Indian, Pacific and Atlantic Ocean, respectively. The contribution of Thaumarchaeota to total prokaryotic DIC fixation increased with depth, particularly in the Atlantic below 1000 m depth and in the lower mesopelagic zone of the Pacific Ocean. Preliminary results from an station in the Atlantic Ocean, combining microautoradiography and fluorescence in situ hybridization (MICRO-CARD-FISH), confirmed that both Thaumarchaeota and some bacterial groups such as SAR 324 take up DIC. Thaumarchaeota and SAR 324 accounted for 7 % and 12% of DIC-positive DAPI-stained cells, respectively, as revealed by MICRO-CARD-FISH. Our results suggest that some phylogenetic groups may be significant contributors to the dark ocean chemoautotrophy

Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)

Original research paperAnthropogenic pressures are changing the magnitude and nature of matter inputs into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area. In order to assess short-term responses in biomass, production, and respiration of heterotrophic bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6 microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and primarily limited by C in autumn. Production responded more than biomass to increasing inputs of matter, whereas respiration did not change. The bacterial production response to increasing dissolved organic C load associated with riverine and atmospheric inputs was strongly related to the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that bacterial production might decrease with the increase of P-deficient allochthonous matter inputs, which would have important biogeochemical consequences for C cycling in coastal areas.Spanish Ministry of Science and Innovation, MINECO, CSIC, Xunta of Galicia and European Union (Marie Curie Grants)Versión del edito

Bacterial community composition and optical signature of DOM shape empirical leucine-to-carbon conversion factors in north-eastern Atlantic waters (0-4000 m)

Oral communicationMicrobial heterotrophic activity is a major process regulating the flux of dissolved organic matter (DOM) in the ocean. DOM quantity and quality strongly influence its microbial utilization and fate in the ocean. In order to broaden the vertical resolution of leucine-to-carbon conversion factors (CFs), needed for converting substrate incorporation into biomass production by heterotrophic bacteria, nine dilution experiments were performed in the north Atlantic. We found a very consistent depth-stratification in empirical CFs values from epipelagic to bathypelagic waters (3.95 ± 0.05 to 0.90 ± 0.51 kg C mol Leu-1). Our results demonstrated that the customarily used CF of 1.55 kg C mol Leu-1 in oceanic waters leads to an underestimation of prokaryotic heterotrophic production in epi- and mesopelagic waters, while it causes a severe overestimation in bathypelagic waters. Pearson correlations showed that CFs were related not only to hydrographic variables but also to specific phylogenetic groups and DOM quality and quantity indicators. Furthermore, a multiple linear regression model predicting CFs from relatively simple hydrographic and optical spectroscopic measurements is provided. Taken together, our results suggest that differences in CFs throughout the water column might be mostly associated to the quality of DOM affecting the response of particular phylogenetic groups.ASL

Bacterioplankton responses to riverine and atmospheric inputs in a coastal upwelling system (Ría de Vigo, NW Spain)

12 páginas, 5 figuras, 2 tablasAnthropogenic pressures are changing the magnitude and nature of matter inputs into the ocean. The Ría de Vigo (NW Spain) is a highly productive and dynamic coastal system that is likely affected by such alterations. Previous nutrient-addition microcosm experiments conducted during contrasting hydrographic conditions suggested that heterotrophic bacteria are limited by organic carbon (C) and occasionally co-limited by inorganic nutrients in this coastal area. In order to assess short-term responses in biomass, production, and respiration of heterotrophic bacteria from the Ría de Vigo to increasing amounts of natural inputs of matter, we conducted 6 microcosm experiments, wherein surface seawater collected in spring, summer, and autumn was mixed with increasing amounts of dissolved natural matter concentrates from riverine and atmospheric origin. Simultaneous experiments with controlled inorganic and/or organic additions indicated that bacteria were co-limited by inorganic nutrients and C in spring and summer and primarily limited by C in autumn. Production responded more than biomass to increasing inputs of matter, whereas respiration did not change. The bacterial production response to increasing dissolved organic C load associated with riverine and atmospheric inputs was strongly related to the relative phosphorus (P) content of the dissolved matter concentrates. Our data suggest that bacterial production might decrease with the increase of P-deficient allochthonous matter inputs, which would have important biogeochemical consequences for C cycling in coastal areasThis research was supported by the Spanish Ministry of Science and Innovation through project REIMAGE (grants CTM2011-30155-C03-01 and CTM2011-30155-C03-02) and by the Xunta the Galicia trough project DIMENSION (grant EM2013/023). E. B-L was funded by a F.P.I. MICINN fellowship. M.N.-C. was funded by the CSIC Program "Junta para la Ampliación de Estudios" co-financed by the ESF. S.M.G. was funded by a Marie Curie fellowshipPeer reviewe

Functional responses of key marine bacteria to environmental change – toward genetic counselling for coastal waters

Coastal ecosystems deteriorate globally due to human-induced stress factors, like nutrient loading and pollution. Bacteria are critical to marine ecosystems, e.g., by regulating nutrient cycles, synthesizing vitamins, or degrading pollutants, thereby providing essential ecosystem services ultimately affecting economic activities. Yet, until now bacteria are overlooked both as mediators and indicators of ecosystem health, mainly due to methodological limitations in assessing bacterial ecosystem functions. However, these limitations are largely overcome by the advances in molecular biology and bioinformatics methods for characterizing the genetics that underlie functional traits of key bacterial populations – “key” in providing important ecosystem services, being abundant, or by possessing high metabolic rates. It is therefore timely to analyze and define the functional responses of bacteria to human-induced effects on coastal ecosystem health. We posit that categorizing the responses of key marine bacterial populations to changes in environmental conditions through modern microbial oceanography methods will allow establishing the nascent field of genetic counselling for our coastal waters. This requires systematic field studies of linkages between functional traits of key bacterial populations and their ecosystem functions in coastal seas, complemented with systematic experimental analyses of the responses to different stressors. Research and training in environmental management along with dissemination of results and dialogue with societal actors are equally important to ensure the role of bacteria is understood as fundamentally important for coastal ecosystems. Using the responses of microorganisms as a tool to develop genetic counselling for coastal ecosystems can ultimately allow for integrating bacteria as indicators of environmental change

Empirical leucine-to-carbon conversion factors for estimating heterothrophic bacterial production in surface waters of the world oceans

Comunicación oralBacterial biomass production is a key parameter for evaluating the role of bacterioplankton in ocean carbon cycling. However, bacterial production cannot be directly measured and is typically estimated from the incorporation rates of radiolabelled leucine. The conversion of leucine uptake rates into bacterial carbon production rates requires the use of conversion factors (CFs) which must be empirically determined. Despite the empirical leucine-to-carbon CFs vary widely across environments very little is known about its potential controlling factors. We conducted a set of 10 surface seawater cultures experiments where the growth of the natural bacterial assemblage was promoted by filtration (removal of grazers) or by both filtration and dilution. Sampling stations were located between 30 ºN and 30 ºS, including the Atlantic, Pacific and Indian oceans. CFs varied from 0.13 to 1.47 Kg C mol Leu-1, being higher in the filtrated than in the filtrated and diluted treatment. The abundance of picocyanobacteria explained 60% of the observed variability. Our results further suggest that the composition of bacterioplankton, as assessed by ARISA fingerprinting, may partially explain the observed variation in CFs

Biogeography of planktonic bacterial communities across the whole Mediterranean Sea

Bacterial population distribution in the Mediterranean Sea has been mainly studied by considering small geographical areas or specific phylogenetic groups. The present study is a molecular microbiology investigation aimed to identify the environmental factors driving total bacterioplankton community composition of seawater samples collected along a transect covering the whole Mediterranean Sea. We performed automated ribosomal intergenic sequence analysis (ARISA) and microscope evaluation of prokaryotic abundance of seawater sampled across both vertical profiles and longitudinal transects in the whole basin. Prokaryotic abundance decreased with depth at all the stations and presented similar values in epi-, meso- and bathypelagic layers across the whole Mediterranean Sea. However, peculiar bacterial assemblages were selected along a longitudinal transect in the epipelagic layers of the eastern and western sub-basins. Vertical differences of the bacterial communities were observed only when considering the epi- and bathypelagic waters, while the study of the structure of bacterial communities at a finer scale across the water column displayed higher variability at the intermediate layers. Nonetheless, different physico-chemical factors were significantly related to the distribution of bacterial populations, both according to geographic position and down the water column in the whole Mediterranean Sea. These results demonstrated that bacterial assemblages are putatively correlated to different water masses of the complex hydrographical systems of the eastern and western Mediterranean sub-basins

Functional responses of key marine bacteria to environmental change – toward genetic counselling for coastal waters

Coastal ecosystems deteriorate globally due to human-induced stress factors, like nutrient loading and pollution. Bacteria are critical to marine ecosystems, e.g., by regulating nutrient cycles, synthesizing vitamins, or degrading pollutants, thereby providing essential ecosystem services ultimately affecting economic activities. Yet, until now bacteria are overlooked both as mediators and indicators of ecosystem health, mainly due to methodological limitations in assessing bacterial ecosystem functions. However, these limitations are largely overcome by the advances in molecular biology and bioinformatics methods for characterizing the genetics that underlie functional traits of key bacterial populations – “key” in providing important ecosystem services, being abundant, or by possessing high metabolic rates. It is therefore timely to analyze and define the functional responses of bacteria to human-induced effects on coastal ecosystem health. We posit that categorizing the responses of key marine bacterial populations to changes in environmental conditions through modern microbial oceanography methods will allow establishing the nascent field of genetic counselling for our coastal waters. This requires systematic field studies of linkages between functional traits of key bacterial populations and their ecosystem functions in coastal seas, complemented with systematic experimental analyses of the responses to different stressors. Research and training in environmental management along with dissemination of results and dialogue with societal actors are equally important to ensure the role of bacteria is understood as fundamentally important for coastal ecosystems. Using the responses of microorganisms as a tool to develop genetic counselling for coastal ecosystems can ultimately allow for integrating bacteria as indicators of environmental change

Functional responses of key marine bacteria to environmental change - toward genetic counselling for coastal waters

Coastal ecosystems deteriorate globally due to human-induced stress factors, like nutrient loading and pollution. Bacteria are critical to marine ecosystems, e.g., by regulating nutrient cycles, synthesizing vitamins, or degrading pollutants, thereby providing essential ecosystem services ultimately affecting economic activities. Yet, until now bacteria are overlooked both as mediators and indicators of ecosystem health, mainly due to methodological limitations in assessing bacterial ecosystem functions. However, these limitations are largely overcome by the advances in molecular biology and bioinformatics methods for characterizing the genetics that underlie functional traits of key bacterial populations - "key" in providing important ecosystem services, being abundant, or by possessing high metabolic rates. It is therefore timely to analyze and define the functional responses of bacteria to human-induced effects on coastal ecosystem health. We posit that categorizing the responses of key marine bacterial populations to changes in environmental conditions through modern microbial oceanography methods will allow establishing the nascent field of genetic counselling for our coastal waters. This requires systematic field studies of linkages between functional traits of key bacterial populations and their ecosystem functions in coastal seas, complemented with systematic experimental analyses of the responses to different stressors. Research and training in environmental management along with dissemination of results and dialogue with societal actors are equally important to ensure the role of bacteria is understood as fundamentally important for coastal ecosystems. Using the responses of microorganisms as a tool to develop genetic counselling for coastal ecosystems can ultimately allow for integrating bacteria as indicators of environmental change.We thank for the many inspiring discussions with Ulla Li Zweifel and Åke Hagström on taking advantage of microbial genetic blueprints for informing on the health status of natural waters. We gratefully acknowledge Martin Brusin for contributing drawings of Figure 1. Research on this subject was supported by the marine strategic research program EcoChange to J. P and the BONUS BLUEPRINT project, which has received funding from BONUS, the Joint Baltic Sea Research and Development Program (Art 185), and Swedish, German and Danish research councils to JP, AA, ML and LR.Peer reviewe

Epidemiological trends of HIV/HCV coinfection in Spain, 2015-2019

Altres ajuts: Spanish AIDS Research Network; European Funding for Regional Development (FEDER).Objectives: We assessed the prevalence of anti-hepatitis C virus (HCV) antibodies and active HCV infection (HCV-RNA-positive) in people living with HIV (PLWH) in Spain in 2019 and compared the results with those of four similar studies performed during 2015-2018. Methods: The study was performed in 41 centres. Sample size was estimated for an accuracy of 1%. Patients were selected by random sampling with proportional allocation. Results: The reference population comprised 41 973 PLWH, and the sample size was 1325. HCV serostatus was known in 1316 PLWH (99.3%), of whom 376 (28.6%) were HCV antibody (Ab)-positive (78.7% were prior injection drug users); 29 were HCV-RNA-positive (2.2%). Of the 29 HCV-RNA-positive PLWH, infection was chronic in 24, it was acute/recent in one, and it was of unknown duration in four. Cirrhosis was present in 71 (5.4%) PLWH overall, three (10.3%) HCV-RNA-positive patients and 68 (23.4%) of those who cleared HCV after anti-HCV therapy (p = 0.04). The prevalence of anti-HCV antibodies decreased steadily from 37.7% in 2015 to 28.6% in 2019 (p < 0.001); the prevalence of active HCV infection decreased from 22.1% in 2015 to 2.2% in 2019 (p < 0.001). Uptake of anti-HCV treatment increased from 53.9% in 2015 to 95.0% in 2019 (p < 0.001). Conclusions: In Spain, the prevalence of active HCV infection among PLWH at the end of 2019 was 2.2%, i.e. 90.0% lower than in 2015. Increased exposure to DAAs was probably the main reason for this sharp reduction. Despite the high coverage of treatment with direct-acting antiviral agents, HCV-related cirrhosis remains significant in this population