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Identfication and Characterization of Ecologically Relevant Lignin-Degrading Bacteria from Coastal Marine Environments


PIs: Mary Ann Moran and Robert E. Hodson (Dept of Marine Sciences, Univ of Georgia, Athens, GA, USA)

Support: Georgia Sea Grant College Program (R/AT-1)

Timeframe: 9/1/96 - 2/28/99 (complete)

Project Overview:
This project used molecular microbial ecology techniques to identify ecologically-relevant bacterial degraders of lignin and lignin-rich pulp mill effluents in coastal Georgia environments. Specifically, we: 1) used innovative techniques to develop culture collections of lignin- and pulp mill waste-degrading bacteria; 2) used molecular methods to identify ecologically relevant isolates from among the organisms gathered into the culture collections; 3) used molecular methods to identify and determine phylogenetic affinities of ecologically relevant bacterial which are presently unculturable; and 4) characterized important isolates with regard to degradative abilities and phylogenetic affinities.

Findings:
Traditional microbiological methods and new molecular techniques were utilized together in a successful project to identify natural estuarine and coastal ocean bacteria that are capable of degrading lignin and lignin-related aromatic monomers. A new bacterial genus (Sagittula) was discovered and described based on a lignin-degrading organism in one of our culture collections, and this bacterium (Sagittula stellata) serves as the type species. This organism was subsequently found to be a member of a phylogenetic cluster of marine bacteria (placed within the alpha subclass of the Proteobacteria) that dominate coastal regions of the southeastern U.S. (accounting for up to 30% of the bacterial DNA), and possibly plays an important ecological role in degrading lignins, humic substances, and other naturally-occurring aromatic compounds. Enzyme assays of this bacterium and other related organisms from our culture collections indicate the presence of ring-cleavage dioxygenase enzymes, proteins which play a critical role in cleaving aromatic rings during degradation of a variety of aromatic compounds.

Publications:
González, J. M. H., W. B. Whitman, R. E. Hodson, and M. A. Moran. 1996. Identifying numerically abundant culturable bacteria from complex communities: an example from a lignin enrichment culture. Applied and Environmental Microbiology 62:4433-4440.

González, J. M., F. Mayer, M. A. Moran, R. E. Hodson, and W. B. Whitman. 1997. Sagittula stellata gen. nov., sp. nov., a lignin-transforming bacterium from a coastal environment. International Journal of Systematic Bacteriology 47:773-780.

González, J. M., and M. A. Moran. 1997. Numerical dominance of a group of marine bacteria in the -subclass of Proteobacteria in coastal seawater. Applied and Environmental Microbiology 63:4237-4242.


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This page was updated October 13, 2006