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Lignin Degradation by Typical Bacteria from Coastal Seawater: the Marine Alpha Cluster

PI: Mary Ann Moran (Dept of Marine Sciences, Univ of Georgia, Athens, GA, USA)

Support: Georgia Sea Grant College Program (R/AT-6)

Timeframe: 3/21/98 - 2/28/01 (complete)

Project Overview:
1. To isolate and identify bacteria from the newly-recognized Marine Alpha cluster that are capable of transforming pulp and paper industry wastes and naturally-occurring lignins and humic substances.
2. To use molecular techniques to identify and quantify lignin-degrading Marine Alpha bacteria in coastal Georgia environments, including areas impacted by pulp industry wastes.
3. To use molecular techniques to quantify lignin-degrading Marine Alpha bacteria in laboratory enrichment studies using industry wastes and other lignin-related compounds.
4. To use microbiological techniques to characterize the physiological abilities of Marine Alpha isolates, including rates of degradation of pulp mill wastes, naturally-occurring lignins and humic substances, and other aromatic compounds.

       Results from this project are beginning to provide insights into the identity of marine bacteria involved in the degradation of aromatic compounds in coastal regions of the southeastern US. Detailed studies are providing information on the enzymology and organization of a family of ring-cleavage dioxygenase genes of potential interest for biotechnological and bioremediative purposes.
       We have characterized aromatic compound degradation by culturable marine Alpha bacteria isolated from coastal Georgia environments. Experiments measured rates of degradation of simple (i.e. single ring) and complex (i.e. lignin) aromatic compounds. Enzymology-based approaches were used to characterize activity levels of two important enzymes in the degradation pathway of aromatic compounds in selected isolates: protocatechuate 3,4 dioxygenase and catechol 1,2 dioxygenase. These enzymes occupy key, rate-limiting positions in the pathway for aromatic ring degradation in many prokaryotes. Our coastal marine bacteria had activity levels comparable to those measure previously for soil bacteria, including members of the genera Pseudomonas, and Acinetobacteri, which have served as model organisms for much of the previous microbiological and biochemical studies of aromatic ring cleavage by prokaryotes.
        Ring-cleavage dioxygenases and related genes have been cloned and sequenced from the two coastal Georgia marine bacteria.

González, J.M., R.E. Hodson and M.A. Moran. 1999. Bacterial populations in replicate marine enrichment cultures: Assessing variability in abundance using 16S rRna-based probes. Hydrobiologia. 401:69-75.

Buchan, A., E. L. Neidle, and M. A. Moran. 2001. Diversity of the ring-cleaving dioxygenase gene pcaH in a saltmarsh bacterial community. Appl. Env. Microbiol. 67:5801-5809.

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This page was updated October 13, 2006