Covert, J. S.. University of Georgia, phloe@arches.uga.edu
Lala, P. S.. University of Georgia, preethi_lala@hotmail.edu
Moran, M. A.. University of Georgia, mmoran@arches.uga.edu

 
COMPOSITION OF MARINE BACTERIAL COMMUNITIES UTILIZING HIGH AND LOW MOLECULAR WEIGHT FRACTIONS OF DISSOLVED ORGANIC MATTER
 
DOM from a southeastern U.S. estuary was separated into high- and low- molecular weight fractions via ultrafiltration and used to establish enrichment cultures. The DOM fractions were inoculated with natural marine bacteria and incubated for six weeks, after which bulk community DNA was extracted to characterize bacterial community composition by 16S rDNA sequence analysis. Analysis of 16S rDNA clone libraries showed substantial differences in community composition between enrichments, with little overlap among the dominant groups. The <1000 MW DOM enrichment was characterized by an abundance of gamma- and epsilon- Proteobacteria, while the >1000 MW DOM was characterized by alpha- and beta-Proteobacteria. Many of the clones from both size fractions clustered with major lineages of marine bacteria previously identified from oceanic clone libraries. Concurrent measurements of cumulative oxygen consumption showed clear differences in biological quality of the DOM fractions, with the <1000 MW fraction supporting ten times more utilization of organic carbon than the >1000 MW fraction. These data suggest that it may eventually be possible to identify marine bacterial groups that specialize in utilizing specific chemical components of the DOM pool, and point to the value of attempting to reconcile molecular biology-based characterizations of bacterial communities with broader biogeochemical issues.
 
Day: Wednesday, Feb. 3
Time: 09:15 - 09:30am
Location: Hilton of Santa Fe
 
Code: SS38WE0915H