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Dicarboxylate transport by rhizobia
Svetlana N Yurgel1, Michael L Kahn
1Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA. syurgel@wsu.edu
FEMS Microbiology Reviews
|September 18, 2004
Summary
Rhizobia bacteria fix nitrogen for legumes using dicarboxylate transport (Dct) systems. This study explores the DctA protein and its role in nutrient uptake for symbiotic nitrogen fixation.
Area of Science:
- Microbiology
- Plant-microbe interactions
- Biochemistry
Background:
- Rhizobia are soil bacteria that form symbiotic relationships with legumes, converting atmospheric nitrogen into ammonia.
- Dicarboxylate transport (Dct) systems are crucial for this symbiosis, supplying rhizobia with energy and carbon.
- The Dct system typically involves the DctA carrier protein and the DctB/DctD regulatory system.
Purpose of the Study:
- To investigate the role and characteristics of the DctA protein in rhizobial symbiosis.
- To discuss models of substrate recognition for DctA and DctB.
- To explore alternative mechanisms regulating DctA expression.
Main Methods:
- Analysis of dicarboxylate transport mechanisms in rhizobia.
- Review of existing evidence on DctA and DctB/DctD function.
- Discussion of mutagenesis data for S. meliloti DctA.
- Comparison of DctA structure with related transporter families.
Main Results:
- Dicarboxylates are vital energy and carbon sources for nitrogen-fixing rhizobia.
- DctA and DctB/DctD exhibit distinct substrate specificities.
- An uncharacterized mechanism can induce DctA expression during symbiosis in some rhizobia.
- Mutagenesis studies support DctA's structural similarity to glutamate transporters.
Conclusions:
- Dicarboxylate transport is essential for effective nitrogen fixation in legume symbiosis.
- The DctA protein, part of the glutamate transporter family, plays a key role in nutrient import.
- Further research is needed to fully elucidate DctA structure and alternative regulatory pathways.