Clade-specific quantitative analysis of photosynthetic gene expression in prochlorococcus

© 2015 Fernández-Pinos et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Newly designed primers targeting rbcL (CO2 fixation), psbA (photosystem II) and rnpB (reference) genes were used in qRT-PCR assays to assess the photosynthetic capability of natural communities of Prochlorococcus, the most abundant photosynthetic organism on Earth and a major contributor to primary production in oligotrophic oceans. After optimizing sample collection methodology, we analyzed a total of 62 stations from the Malaspina 2010 circumnavigation (including Atlantic, Pacific and Indian Oceans) at three different depths. Sequence and quantitative analyses of the corresponding amplicons showed the presence of high-light (HL) and low-light (LL) Prochlorococcus clades in essentially all 182 samples, with a largely uniform stratification of LL and HL sequences. Synechococcus cross-amplifications were detected by the taxon-specific melting temperatures of the amplicons. Laboratory exposure of Prochlorococcus MED4 (HL) and MIT9313 (LL) strains to organic pollutants (PAHs and organochlorine compounds) showed a decrease of rbcL transcript abundances, and of the rbcL to psbA ratios for both strains. We propose this technique as a convenient assay to evaluate effects of environmental stressors, including pollution, on the oceanic Prochlorococcus photosynthetic function

High atmosphere-ocean exchange of semivolatile aromatic hydrocarbons

Polycyclic aromatic hydrocarbons, and other semivolatile aromatic-like compounds, are an important and ubiquitous fraction of organic matter in the environment. The occurrence of semivolatile aromatic hydrocarbons is due to anthropogenic sources such as incomplete combustion of fossil fuels or oil spills, and other biogenic sources. However, their global transport, fate and relevance for the carbon cycle have been poorly assessed, especially in terms of fluxes. Here we report a global assessment of the occurrence and atmosphere-ocean fluxes of 64 polycyclic aromatic hydrocarbons analysed in paired atmospheric and seawater samples from the tropical and subtropical Atlantic, Pacific and Indian oceans. The global atmospheric input of polycyclic aromatic hydrocarbons to the global ocean is estimated at 0.09 Tg per month, four times greater than the input from the Deepwater Horizon spill. Moreover, the environmental concentrations of total semivolatile aromatic-like compounds were 10 2 -10 3 times higher than those of the targeted polycyclic aromatic hydrocarbons, with a relevant contribution of an aromatic unresolved complex mixture. These concentrations drive a large global deposition of carbon, estimated at 400 Tg C yr -1, around 15% of the oceanic CO uptake.This work was funded by the Spanish Ministry of Economy and Competitiveness (Circumnavigation Expedition Malaspina 2010: Global Change and Biodiversity Exploration of the Global Ocean. CSD2008-00077). B.G.-G. and M.-C.F.-P. acknowledge a predoctoral fellowship from BBVA Foundation and the Spanish National Research Council (CSIC), respectively. CSIC and the Spanish Government are also acknowledged for additional financial support.Peer Reviewe

Photosynthetic gene expression responses of the oceanic ubiquitous cyanobacterium Prochlorococcus due to changes of environmental variables

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainThe cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on Earth [1]. Being a main global primary producer and ubiquist in the tropical and subtropical regions of the world’s oceans [2], it constitutes a good sentinel species for evaluating the effect of environmental stressors on oceanic photosynthesis. We developed a sensitive method to monitor the expression of two genes responsible of photosynthesis in Prochlorococcus, rbcL (RuBisCO) and psbA (D1 protein), using rnpB as reference gene [3,4]. We applied the method to samples from 63 stations of the Malaspina circumnavigation cruise (December 2010 - July 2011), sampled at three depths. In addition, natural communities of nano-and picoplankton were experimentally exposed to organic pollutant mixtures. Expression of Prochlorococcus rbcL and psbA genes correlated with several physical variables and other biological measurements, and were sensitive to low levels of organic pollutant mixtures. We consider these sublethal effects on the photosynthesis, together with already known effects at cellular level [5,6], are significant potential perturbators of the oceanic carbon cycle. This confirms the anthropogenic chemosphere as a vector of global change during the Anthropocene. 1. Bryant DA 2003 Proc Natl Acad Sci USA 100:9647-9649 2. Partensky F et al. 1999 Microbiol Mol Biol Rev 63:106-127 3. Martiny AC et al. 2006 Proc Natl Acad Sci USA 103:12552-12557 4. Gomez-Baena G et al 2009 Res Microbiol 160:567-575 5. Echeveste P et al. 2010 Chemosphere 81:161-168 6. Echeveste P et al. 2011 Environ Pollut 159:1307-1316Peer Reviewe

Effects of organic pollutants on oceanic photosynthetic function mediated by Prochlorococcus

Society of Environmental Toxicology and Chemistry (SETAC) Europe 25th Annual Meeting, 3-7 May 2015, Barcelona.-- 2 pages, 4 figuresProchlorococcus is the smallest and most abundant photosynthetic organism known on Earth and a major contributor of ocenic primary production. This cianobacterium is ubiquist in every ocean from 40°N to 40°S, from surface to 200 m depth in the water column, reaching abundances close to 10 cells/mL worldwide [1]. Its large surface/volume ratio gives it a high efficiency for light and nutrients capture. On the other hand, this characteristics also implicate a higher intake and a faster bioconcentration of pollutants, resulting in an extreme sensitivity to a variety of environmental stressors, from UV radiation to organic pollutants [2]. Therefore, Prochlorococcus constitutes an excellent sentinel organism to evaluate the dependence of the photosynthetic function to environmental variables and anthropogenic impacts in middle latitudinal oceans. Over the past century the global phytoplankton concentration has declined and changes in chlorophyll and primary production have been detected, which has been attributed to the impact of global climate change [3]. Global Change is a set of interlinked vectors, being one of the best studied the climate change. Neverthelees, the only vector whose global impact has not been quantifyed yet is chemical pollution [4]. In this way, the main objective of the present work was to measure the photosynthetic capacity of Prochlorococcus in Atlantic, Indian and Pacific oceans during the Malaspina circumnavigation, and study its relationship with the concentrations of diverse organic pollutants. This study was performed within a framework of more than 300 biological, physical and chemical variables, using both field sample collection and experiments on board with wild communitiesThis work was funded by the Spanish Government through the Malaspina project. MC Fernández-Pinos acknowledges a predoctoral fellowship from the Spanish National Research CouncilPeer Reviewe