SS2.05 Phylogenetic and Physiologic Successions in Aquatic Bacterial Communities
Date: Monday, June 10, 2002
Time: 2:00:00 PM
Location: Carson C
 
StepanauskasR, University of Georgia, Athens, USA, ramunas@arches.uga.edu
Moran, M, A, University of Georgia, Athens, USA, mmoran@uga.cc.uga.edu
Bergamaschi, B, A, U.S. Geological Survey, Sacramento, USA, bbergama@usgs.gov
Hollibaugh, J, , University of Georgia, Atehns, USA, aquadoc@uga.edu
 
Environmental controls of bacterioplankton composition in San Francisco Delta
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We examined seasonal and spatial variation in bacterioplankton composition in the San Francisco Delta using terminal restriction fragment length polymorphism (T-RFLP) analysis. Cloned 16S rRNA genes from this system were used to identify taxa represented in the T-RFLP profiles. Principal component analysis of T-RFLP profiles revealed grouping of samples on a seasonal rather than spatial basis. The strongest association with summer/fall communities was demonstrated by Actinomycetes related to Microthrix, beta-Proteobacteria related to Ralstonia, and alfa-Proteobacteria identical to clone LD12. Geobacter-related delta-Proteobacteria and Sanguibacter–related Actinomycetes showed a relative increase during winter/spring, indicating that they were washed out from watershed soils. In an attempt to explain ribotype distribution by environmental controls, a partial least squares regression model was constructed using 14 available X-variables. Four X-variables remained after model optimization: concentration of bioavailable dissolved organic carbon (BDOC), pH, temperature, and river water discharge to the Delta. The highest predictability was achieved for the Ralstonia-, LD12-, and Microthrix- related ribotypes, with corresponding Q^2=0.46, 0.43, and 0.31. These ribotypes were associated with low water discharge and high pH and temperature, indicating that they thrived during summer/autumn conditions with increased primary production and decreased inputs of allochthonous DOC. On the other hand, delta-Proteobacteria and Sanguibacter– related Actinomycetes were associated with high water discharge and low pH and temperature conditions, supporting their terrestrial origin.