Kaplan, L. A. Stroud Water Research Center, lakaplan@stroudcenter.org
, . A. ,

 
DISSOLVED ORGANIC MATTER METABOLISM AS A LINK TO HETEROGENEITY IN COMMUNITIES OF HETEROTROPHIC BACTERIA
 
Two central questions in aquatic sciences are: (1) what determines whether an organic molecule or compound is biodegradable, and (2) how cosmopolitan are the various species of microbiota? If different environments contain the same resource of species, then a reasonable hypothesis is that comparable community structure will develop in habitats when exposed to similar chemical and physical environments. Studies with biofilm communities from streams in diverse biomes showed that each community was able to metabolize 10 to 30% of the DOC present in the streamwater from which it was colonized. However, short-term (hours) and long-term (weeks) cross-feeding experiments with biofilms from one biome and DOC sources from another revealed an inability to metabolize the DOC. I suggest that community acclimation to
 
Day: Thursday, Feb. 4
Time: 09:45 - 10:00am
Location: Sweeney Center
 
Code: SS33TH0945S
POLAR LIPIDS IN DISSOLVED ORGANIC MATTER: STRUCTURE, SOURCES AND LINKS TO ORGANIC MATTER CYCLING Harvey, H. Chesapeake Biological Laboratory, harvey@cbl.umces.edu
Mannino, A. Chesapeake Biological Laboratory, antonio@cbl.umces.edu
Ju, S. Chesapeake Biological Laboratory, ju@cbl.umces.edu

 
POLAR LIPIDS IN DISSOLVED ORGANIC MATTER: STRUCTURE, SOURCES AND LINKS TO ORGANIC MATTER CYCLING
 
Lipids have been used extensively as organic tracers, but little is known about the molecular composition and structural organization of dissolved lipids. Dissolved organic matter (DOM) was collected throughout the Delaware Estuary, concentrated by ultrafiltration into high (1 to 30 kDa) and very high (30 kDa to 0.2 Ám) nominal molecular weight fractions for analysis of structural composition. Analysis by GC-MS found fatty acids as the primary lipid in both fractions, principally the saturated 14, 16 and 18 carbon acids. Fatty acids were also the major lipid in particles, but with a significantly different molecular distribution. TLC-FID was used to separate and quantify the native form of lipids present. Results show that lipids in both dissolved fractions exist mainly as phospholipids and glycolipids, with only minor amounts of other classes. The distributions of phospholipids showed distinctive trends along the estuarine gradient, with phosphatidylcholine a major component in riverine waters and the chlorophyll maximum while phosphatidylethanolamine increased in coastal waters. Recent laboratory studies have shown that adsorption or enclosure of proteins by polar lipids reduces rates of bacterial degradation. Confirmation of the widespread presence of these lipids in DOM provides supports for the hydrophobic interface as an important control over rates of microbial mineralization.
 
Day: Thursday, Feb. 4
Time: 10:30 - 10:45am
Location: Sweeney Center
 
Code: SS33TH1030S