I. Overview

II. Results

III. Current Participants

IV. Publications

V. References

I. Overview
Legumes and bacteria of the genus Rhizobium form an association of great significance to agriculture. The nitrogen-fixing abilities of Rhizobia enable legumes (e.g. beans, alfalfa) to grow without the need for nitrogenous fertilizers that are both expensive and harmful to the environment. Unfortunately, the associative abilities of Rhizobium are confined to the legumes.

Certain nitrogen-fixing cyanobacteria have a much wider range of plants with which they form associations. Cyanobacteria form productive associations with representatives of four major categories of plants: angiosperms (Gunnera), gymnosperms (cycads), ferns (Azolla), and bryophytes (Anthoceros). Unfortunately, productive associations have not been described with any plant that plays a major role in human nutrition.

Recently (Gantar et al, 1991), an association has been observed between a strain (2S9B) of the cyanobacterium Nostoc and wheat, obviously a big name plant. Miro Gantar, a collaborator at Florida International University in Miami, is examining the ability of the Nostoc to support the nitrogen needs of wheat while we here at UR are attempting to develop a means of genetically manipulating the cyanobacterium, so that we can study the process of association.

II. Results
Restriction enzymes, molecular defenses against foreign DNA, must be thwarted before the transfer of DNA into cyanobacteria can proceed to a degree that is of much use (Elhai et al, 1997). With this in mind, we decided to determine the restriction activities possessed by Nostoc 2S9B. Digestion of well-characterized DNA extracts of Nostoc revealed the bad news: the strain has at least four restriction enzymes, any one of which could compromise efforts to perform genetic manipulations.

Rather than use established but labor-intensive methods to overcome restriction (Elhai et al, 1997), we chose a novel approach, one that might be applicable to efforts to overcome... (to be continued)

III. Current Participants

Those pursuing this project will work with Andrey to develop a plasmid that can protect recombinant DNA from the potent defences Nostoc presents against foreign DNA.

IV. Publications
Miroslav Gantar and Jeff Elhai (1999). Colonization of wheat para-nodules by N₂-fixing cyanobacterium Nostoc 2S9B. New Phytologist 141:373-379. Abstract

Miroslav Gantar (1999). Co-cultivation of N₂-fixing cyanobacterium Nostoc sp. strain 2S9B and wheat callus. Symbiosis 29:1-18.

Miroslav Gantar (2000). Mechanical damage of roots provides enhanced colonization of the wheat endorhizosphere by the dinitrogen-fixing cyanobacterium Nostoc sp strain 2S9B. Biology and Fertility of Soils 32:250-255.

V. References
Elhai J, Vepritskiy A, Muro-Pastor AM, Flores E, Wolk CP (1997). Reduction of conjugal transfer efficiency by three restriction activities of Anabaena sp. strain PCC 7120. Journal of Bacteriology 179:1998-2005.

Gantar M, Kerby NW, Obreht Z, and Rowell P (1991). Colonization of wheat (Triticum vulgare L.). I. A survey of soil cyanobacterial isolates forming associations with roots. New Phytologist 118:477-483.