http://www.mdpi.com/journal/marinedrugs/special_issues/metabolomic-approaches/ Dear Colleagues, Marine life has developed unique metabolic and physiologic capabilities to survive in the many varied and complex marine ecosystems. Metabolomics is the systematic study of the small-molecule metabolite profiles of organisms. These metabolites range from metabolic intermediates and hormones to other signaling molecules and secondary metabolites. Obtaining a detailed description of the metabolic pathways for marine organisms can be a key to understanding how these organisms bioprocess many of their novel compounds. This in turn can help efficiently direct the search for biochemicals with the potential to improve the health and quality of life of humans, domestic and wild animals and/or have important impacts on the environment. This special issue dedicated to “Metabolomic Approaches to Marine Organisms” hopes to emphasize the importance of studying and understanding the metabolism of marine organisms and the role this knowledge can play in the realm of marine biodiscovery. As the Guest Editor, I invite scientists working on metabolomic questions studying marine organisms to report recent advances in the field. I look forward to working with you towards a successful special issue of the journal Marine Drugs dedicated to this under studied but important area. Prof. Dr. Michael K. StoskopfProf. Dr. Jeffrey Macdonald Guest Editors Submission All manuscripts should be submitted to marinedrugs@mdpi.com with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Marine Drugs is an international peer-reviewed Open Access monthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this Open Access journal is 1600 CHF per accepted paper. http://www.mdpi.com/1660-3397/9/11/2438/ Possible sources of variation in non-polar secondary metabolites of Portieria hornemannii, sampled from two distinct regions in the Philippines (Batanes and Visayas), resulting from different life-history stages, presence of cryptic species, and/or spatiotemporal factors, were investigated. PCA analyses demonstrated secondary metabolite variation between, as well as within, five cryptic Batanes species. Intraspecific variation was even more pronounced in the three cryptic Visayas species, which included samples from six sites. Neither species groupings, nor spatial or temporal based patterns, were observed in the PCA analysis, however, intraspecific variation in secondary metabolites was detected between life-history stages. Male gametophytes (102 metabolites detected) were strongly discriminated from the two other stages, whilst female gametophyte (202 metabolites detected) and tetrasporophyte (106 metabolites detected) samples were partially discriminated. These results suggest that life-history driven variations, and possibly other microscale factors, may influence the variation within Portieria species. http://www.mdpi.com/1660-3397/9/11/2438/ Mon, 21 Nov 2011 00:00:00 CET Marine Drugs 2011-11-21 9 11 Article 2438 2468 1660-3397 Variability of Non-Polar Secondary Metabolites in the Red Alga Portieria 2011-11-21 doi: 10.3390/md9112438 Dioli Ann Payo Joannamel Colo Hilconida Calumpong Olivier de Clerck http://www.mdpi.com/1660-3397/9/9/1566/ Manila clam Ruditapes philippinarum is one of the most important economic species in shellfishery in China due to its wide geographic distribution and high tolerance to environmental changes (e.g., salinity, temperature). In addition, Manila clam is a good biomonitor/bioindicator in “Mussel Watch Programs” and marine environmental toxicology. However, there are several pedigrees of R. philippinarum distributed in the marine environment in China. No attention has been paid to the biological differences between various pedigrees of Manila clams, which may introduce undesirable biological variation in toxicology studies. In this study, we applied NMR-based metabolomics to detect the biological differences in two main pedigrees (White and Zebra) of R. philippinarum and their differential responses to heavy metal exposures (Cadmium and Zinc) using adductor muscle as a target tissue to define one sensitive pedigree of R. philippinarum as biomonitor for heavy metals. Our results indicated that there were significant metabolic differences in adductor muscle tissues between White and Zebra clams, including higher levels of alanine, glutamine, hypotaurine, phosphocholine and homarine in White clam muscles and higher levels of branched chain amino acids (valine, leucine and isoleucine), succinate and 4-aminobutyrate in Zebra clam muscles, respectively. Differential metabolic responses to heavy metals between White and Zebra clams were also found. Overall, we concluded that White pedigree of clam could be a preferable bioindicator/biomonitor in marine toxicology studies and for marine heavy metals based on the relatively high sensitivity to heavy metals. http://www.mdpi.com/1660-3397/9/9/1566/ Mon, 19 Sep 2011 00:00:00 CEST Marine Drugs 2011-09-19 9 9 Article 1566 1579 1660-3397 NMR-Based Metabolomic Investigations on the Differential Responses in Adductor Muscles from Two Pedigrees of Manila Clam Ruditapes philippinarum to Cadmium and Zinc 2011-09-19 doi: 10.3390/md9091566 Huifeng Wu Xiaoli Liu Jianmin Zhao Junbao Yu http://www.mdpi.com/1660-3397/8/10/2578/ The Eastern oyster (Crassostrea virginica) is a useful, robust model marine organism for tissue metabolism studies. Its relatively few organs are easily delineated and there is sufficient understanding of their functions based on classical assays to support interpretation of advanced spectroscopic approaches. Here we apply high-resolution proton nuclear magnetic resonance (1H NMR)-based metabolomic analysis to C. virginica to investigate the differences in the metabolic profile of different organ groups, and magnetic resonance imaging (MRI) to non-invasively identify the well separated organs. Metabolites were identified in perchloric acid extracts of three portions of the oyster containing: (1) adductor muscle, (2) stomach and digestive gland, and (3) mantle and gills. Osmolytes dominated the metabolome in all three organ blocks with decreasing concentration as follows: betaine > taurine > proline > glycine > ß-alanine > hypotaurine. Mitochondrial metabolism appeared most pronounced in the adductor muscle with elevated levels of carnitine facilitating ß-oxidation, and ATP, and phosphoarginine synthesis, while glycogen was elevated in the mantle/gills and stomach/digestive gland. A biochemical schematic is presented that relates metabolites to biochemical pathways correlated with physiological organ functions. This study identifies metabolites and corresponding 1H NMR peak assignments for future NMR-based metabolomic studies in oysters. http://www.mdpi.com/1660-3397/8/10/2578/ Fri, 08 Oct 2010 00:00:00 CEST Marine Drugs 2010-10-08 8 10 Article 2578 2596 1660-3397 Metabolomic Investigations of American Oysters Using 1H-NMR Spectroscopy 2010-10-08 doi: 10.3390/md8102578 Andrey P. Tikunov Christopher B. Johnson Haakil Lee Michael K. Stoskopf Jeffrey M. Macdonald http://www.mdpi.com/1660-3397/8/10/2546/ Symbioses play an important role within the marine environment. Among the most well known of these symbioses is that between coral and the photosynthetic dinoflagellate, Symbiodinium spp. Understanding the metabolic relationships between the host and the symbiont is of the utmost importance in order to gain insight into how this symbiosis may be disrupted due to environmental stressors. Here we summarize the metabolites related to nutritional roles, diel cycles and the common metabolites associated with the invertebrate-Symbiodinium relationship. We also review the more obscure metabolites and toxins that have been identified through natural products and biomarker research. Finally, we discuss the key role that metabolomics and functional genomics will play in understanding these important symbioses. http://www.mdpi.com/1660-3397/8/10/2546/ Thu, 30 Sep 2010 00:00:00 CEST Marine Drugs 2010-09-30 8 10 Review 2546 2568 1660-3397 Symbiodinium—Invertebrate Symbioses and the Role of Metabolomics 2010-09-30 doi: 10.3390/md8102546 Benjamin R. Gordon William Leggat http://www.mdpi.com/1660-3397/8/8/2369/ The successful applications of magnetic resonance imaging (MRI) in medicine are mostly due to the non-invasive and non-destructive nature of MRI techniques. Longitudinal studies of humans and animals are easily accomplished, taking advantage of the fact that MRI does not use harmful radiation that would be needed for plain film radiographic, computerized tomography (CT) or positron emission (PET) scans. Routine anatomic and functional studies using the strong signal from the most abundant magnetic nucleus, the proton, can also provide metabolic information when combined with in vivo magnetic resonance spectroscopy (MRS). MRS can be performed using either protons or hetero-nuclei (meaning any magnetic nuclei other than protons or 1H) including carbon (13C) or phosphorus (31P). In vivo MR spectra can be obtained from single region ofinterest (ROI or voxel) or multiple ROIs simultaneously using the technique typically called chemical shift imaging (CSI). Here we report applications of CSI to marine samples and describe a technique to study in vivo glycine metabolism in oysters using 13C MRS 12 h after immersion in a sea water chamber dosed with [2-13C]-glycine. This is the first report of 13C CSI in a marine organism. http://www.mdpi.com/1660-3397/8/8/2369/ Thu, 19 Aug 2010 00:00:00 CEST Marine Drugs 2010-08-19 8 8 Article 2369 2383 1660-3397 Applications of Chemical Shift Imaging to Marine Sciences 2010-08-19 doi: 10.3390/md8082369 Haakil Lee Andrey Tikunov Michael K. Stoskopf Jeffrey M. Macdonald http://www.mdpi.com/1660-3397/8/8/2318/ Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO2-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO2 levels (partial pressure of CO2 in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated PCO2 and 15 °C hemolymph pH fell (pHe = 7.1 ± 0.2 (CO2-group) vs. 7.6 ± 0.1 (control)) and PeCO2 values in hemolymph increased (0.5 ± 0.2 kPa (CO2-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO2-incubated oysters ([HCO-3]e = 1.8 ± 0.3 mM (CO2-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pHe did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO2-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO2-incubated group. Investigation in isolated gill cells revealed a similar temperature-dependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na+/K+-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using 1H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks. http://www.mdpi.com/1660-3397/8/8/2318/ Wed, 11 Aug 2010 00:00:00 CEST Marine Drugs 2010-08-11 8 8 Article 2318 2339 1660-3397 Impact of Ocean Acidification on Energy Metabolism of Oyster, Crassostrea gigas—Changes in Metabolic Pathways and Thermal Response 2010-08-11 doi: 10.3390/md8082318 Gisela Lannig Silke Eilers Hans O. Pörtner Inna M. Sokolova Christian Bock