Research Project

Summary

Genomics projects include the study of many kinds of organisms that affect our daily lives - for example, bacteria. One of the major groups of bacteria is also one that few people know - microbes that form nodules on the roots of many plants. Inside these nodules, specialized bacteria convert atmospheric nitrogen into a chemically useful form, which is essential for plant growth and thus ultimately for life on Earth. One of the best-studied nitrogen-fixing bacteria is S. meliloti, which fixes nitrogen in the roots of alfalfa and other plants.

This project aimed to understand more about S. meliloti by using genomic methods to study its genes - how they direct nitrogen fixation and many other biochemical reactions. Using complex genetic methods, the project team constructed light-emitting versions of almost 50% of S. meliloti proteins. This gave them an easy way to measure the amount of these proteins in S. meliloti cells - a reflection of genetic activity - under more than 100 conditions of growth. They used similar genetic methods to remove many individual genes from the S. meliloti genome. This process showed the researchers how the absence of these genes affected bacterial growth under many conditions.  The team used DNA micro-arraying to measure gene-expression from all S. meliloti genes (6,200). The resulting, deeper understanding will lead to better and more environmentally friendly methods of nitrogen fixation for the food and agricultural industries.

Fast Facts

• Highlighted outcome:  A body of knowledge about S. meliloti, a bacterium that fixes nitrogen - an essential process for plant growth.
• Number of research personnel:  28 undergraduates, 9 graduate students, 3 fellows, and 15 technicians.
• Number of peer-reviewed publications: 17 research papers.

Notable Publications
Sibley CD, MacLellan SR, and Finan T. 2006.  The Sinorhizobium meliloti chromosomal origin of replication. Microbiol.  152:443-55.

Yuan ZC, Zaheer R, and Finan TM. 2006.  Regulation and properties of PstSCAB, a high-affinity, high-velocity phosphate transport system of Sinorhizobium meliloti.  J. Bacteriol. 188:1089-1102.

Guo H, Sun S, Finan T, and Xu JP. 2005.  Novel DNA sequences from natural strains of the nitrogen-fixing symbiotic bacterium Sinorhizobium meliloti.  Appl. Environ. Microbiol.  71:7130-8.

Mao C, Qiu J, Wang C, Charles TC, and Sobral BWS. 2005.  NodMutDB: a database for genes and mutants involved in symbiosis. Bioinformatics 21:2927-9.

Yuan Z, Zaheer R, and Finan TM. 2005.  Phosphate limitation induces catalase expression in Sinorhizobium meliloti, Pseudomonas aeruginosa and Agrobacterium tumefaciens. Molec. Microbiol. 58: 877-94.