Gradients in intact polar diacylglycerolipids across the Mediterranean Sea are related to phosphate availability

Abstract

Intact polar membrane lipids compose a significant fraction of cellular material in plankton and their synthesis imposes a substantial constraint on planktonic nutrient requirements. As a part of the Biogeochemistry from the Oligotrophic to the Ultraoligtrophic Mediterranean (BOUM) cruise we examined the distribution of several classes of intact polar diacylglycerolipids (IP-DAGs) across the Mediterranean, and found that phospholipid concentration as a percent of total lipids correlated with phosphate concentration. In addition, the ratios of non-phosphorus lipids to phospholipids – sulfoquinovosyldiacylglycerol (SQDG) to phosphatidylglycerol (PG), and betaine lipids to phosphatidylcholine (PC) – were also found to increase from west to east across the Mediterranean. Additionally, microcosm incubations from across the Mediterranean were amended with phosphate and ammonium, and in the course of several days nutrient amendments elicited a shift in the ratios of IP-DAGs. These experiments were used to assess the relative contribution of community shifts and physiological response to the observed change in IP-DAGs across the Mediterranean. The ratio of SQDG to chlorophyll $a$ was also explored as an indicator of phytoplankton response to nitrogen availability. This study is the first to demonstrate the dynamic response of membrane lipid composition to changes in nutrients in a natural, mixed planktonic community

Marine microbial intact polar diacylglycerolipids and their application in the study of nutrient stress and bacterial production

“…Given the diverse locations of these samples it is unsurprising that the relative distribution of IP-DAGs varied across the three samples ( Figure 3). IP-DAG concentrations calculated by the two methods were of the same order of magnitude for all six IP-DAG classes analyzed in all three samples, and were similar to published IP-DAG concentrations from other marine samples (Brandsma et al, 2012;Popendorf et al, 2011b;. Both methods found similar relative distributions of IP-DAGs in each sample, with phospholipids being relatively abundant in the Benguela upwelling sample, all IP-DAGs being at relatively low concentrations in the Mid-Atlantic sample, and glycolipids being relatively abundant in the Uruguayan coast ( Figure 3).…”

“…This is likely particularly true for IP-DAG classes that have many molecular ions all at low concentrations, such as DGDG, where each integrated peak has a relatively low signal to noise ratio and thus integration of each smoothed peak adds some amount of error. For DGDG, which is generally at low concentrations in the ocean (Table 4; Popendorf et al 2011b) the summation of seven chromatograms in the ITMS method seems to lead to highly variable results relative to the TQMS method.…”

“…Led by advances in high performance liquid chromatography/electrospray ionization ion-trap mass spectrometry (HPLC-ESI-ITMS) methods we have established that IP-DAGs in the upper ocean are dominated by glycolipids, phospholipids, sulfolipids and betaine lipids (Popendorf et al, 2011b;Schubotz et al, 2009;) (SM Figure 1) . Phospholipids from marine microbes have been well studied Suzumura and Ingall, 2001;Van Mooy et al, 2008;White, 1988), however the latter two classes of molecules, sulfolipids and betaine lipids, were largely unknown to chemical oceanography until recently (Schubotz et al, 2009;, and appear to be significantly more abundant in the surface ocean than phospholipids (Brandsma et al, 2012;Popendorf et al, 2011b;Schubotz et al, 2009;.…”

“…Phospholipids from marine microbes have been well studied Suzumura and Ingall, 2001;Van Mooy et al, 2008;White, 1988), however the latter two classes of molecules, sulfolipids and betaine lipids, were largely unknown to chemical oceanography until recently (Schubotz et al, 2009;, and appear to be significantly more abundant in the surface ocean than phospholipids (Brandsma et al, 2012;Popendorf et al, 2011b;Schubotz et al, 2009;.…”

“…In addition, sulfolipids and betaine lipids have shown utility as indicators of nutrient stress and stoichiometric flexibility Popendorf et al, 2011b;. Quantification of IP-DAGs at the class level is of particular interest, as the heteroatoms that distinguish headgroup classes (e.g.…”