Intact polar diacylglycerol biomarker lipids isolated from suspended particulate organic matter accumulating in an ultraoligotrophic water column

Abstract

Intact polar diacylglycerols (IP-DAGs) are essential components of cell membranes. Because they are structurally diverse and hypothesized to represent primarily living cells, they are potential molecular markers for a recent contribution by microbial communities to various carbon reservoirs. This study employed a novel molecular networking approach to investigate the evolution of IP-DAG structural diversity with depth in an ultraoligotrophic environment of the western South Pacific Ocean to test the hypothesis that particle transport to depth is rapid enough to preserve the IP-DAG biomarker signature of the photosynthetic community. IP-DAG profiles for several cultured cyanobacteria and photosynthetic picoeukaryotes were used as templates for constructing molecular networks to compare and interpret IP-DAG signatures of suspended particles isolated from a water column depth profile. Analysis of corresponding genetic community composition data for the same field samples was used to connect IP-DAG structures with their likely biological sources. Our data show that, although most IP-DAG classes associated with photosynthetic organisms were not observed below the euphotic zone, several other IP-DAG classes in deep samples might provide interesting targets for future studies seeking to examine the in situ contribution of deep sea microbes to suspended particulate organic matter (POM). Overall, the results represent the deepest water column IP-DAG dataset to date and demonstrate the utility of molecular networking for analyzing and visualizing complex environmental datasets.

Planktonic Lipidome Responses to Aeolian Dust Input in Low-Biomass Oligotrophic Marine Mesocosms

“…avg. = 30.4 ± 0.7; Figures 4A, 5) and saturated compared to those described in the surface equatorial N. Pacific (Van Mooy and Fredricks, 2010) or produced in algal cultures (Kato et al, 1996), including picoeukaryotes (Kharbush et al, 2016). The absence of the long chain C 22:6 fatty acid further discounts a eukaryotic source of PC (cf.…”

“…same filters (Brandsma et al, 2012;Kharbush et al, 2016). The oligotrophic conditions and relatively lower amounts of biomass in the mesocosms investigated during the current study may thus explain why PG and PE were below the limit of detection.…”

“…While no GSL has been reported by previous IPL surveys of surface seawater (Van Mooy and Fredricks, 2010;Popendorf et al, 2011b;Brandsma et al, 2012;Kharbush et al, 2016), GSLs have been associated with anaerobic production in subsurface FIGURE 9 | Correlated changes in IPL relative abundance with τ PO4 and fractional phosphate uptake by plankton >2 µm in control mesocosms (circles) and those amended with Saharan dust (squares) or mixed aerosol (triangles) and collected on day −1 (light gray), day 3 (dark gray), or day 6 (black).…”

“…Recent advances in lipid analysis via tandem ultra high pressure liquid chromatography mass spectrometry (UHPLC-MS) now allow rapid and enhanced detection of intact polar lipids (IPLs) as well as structural elucidation of their polar headgroups and alkyl chains (e.g., Wörmer et al, 2013). Sophisticated molecular networks have also been employed to facilitate the interpretation of the large data sets obtained by such analyses (Kharbush et al, 2016).…”

Perspectives on Chemical Oceanography in the 21st century: Participants of the COME ABOARD Meeting examine aspects of the field in the context of 40 years of DISCO

“…Research on the cycling of specific organic compounds through proteomics, metabolomics, lipidomics and the chemical and structural characterization of organic matter represent Emerging areas of Chemical Oceanography. These types of measurements (e.g., Collins et al, 2016;Heal et al, 2017;Kharbush et al, 2016;Kido Soule et al, 2015;Koch et al, 2005;Pearson, 2014;Slattery et al, 2012) may have a solid theoretical basis but their interpretive power is currently limited by the extent of application. For example, marine proteomics studies have revealed physiological responses of Southern Ocean phytoplankton to changing environmental conditions (Boyd et al, 2016), identified combined nutrient stressors in the Pacific Ocean , and been used to track organic nitrogen sources from the water column to sediment burial in the Bering Sea (Moore et al, 2012), demonstrating the field's emerging interpretive power.…”