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Fact Sheet: Commercialization of Sinorhizobium (Rhizobium) Meliloti, RMBPC-2

In September 1997, the Environmental Protection Agency (EPA) approved limited commercialization of the intergeneric microorganism Sinorhizobium meliloti (S. meliloti) strain RMBPC-2. The microorganism will be used as a microbial seed inoculant to coat alfalfa seeds prior to planting. The company that will be manufacturing and distributing the new seed inoculant is Research Seeds, Inc., which is located in St. Joseph, MO. The company will be allowed to manufacture up to a maximum production volume of 500,000 pounds of the microbial seed inoculant during any consecutive 12-month period. Prior to attaining that production volume, the company is required to notify the Agency so that EPA may assess the need for additional data on the microorganism.


Rhizobia are a group of bacteria, encompassing the generaRhizobium, Sinorhizobium and Bradyrhizobium, normally found in soil, which establish mutually beneficial (symbiotic) relationships with legumes. Rhizobia form growths called nodules (nodulation) on the roots of the legumes, and provide usable nitrogen to the plants. In return, the plants provide a carbon and energy source for the rhizobia.

Nitrogen is an essential nutrient for healthy plant growth. Although abundant in the air and in organic matter in the soil, plants are unable to use nitrogen in these forms. Conventional methods of providing nitrogen to plants in a usable form include adding nitrogen rich fertilizers to the soil, or inoculating seed (i.e., coating the seed) with bacteria able to perform a process called nitrogen fixation. Nitrogen fixation is the process of converting atmospheric nitrogen into an inorganic form that plants can use. Nitrogen "fixing" bacteria not only provide nitrogen to the plants they nodulate, but also leave behind excess nitrogen in the soil, potentially reducing the need for nitrogen fertilizers the next growing season. Rhizobia fix nitrogen for legumes, and S. meliloti is specific to the legumes alfalfa, sweet clover and fenugreek. Prior to 1994, S. meliloti was classified as Rhizobium meliloti (R. meliloti).

Rhizobia have been used commercially as seed inoculants in the form of seed coatings for over one hundred years. Currently, about 80% of alfalfa grown in the United States is inoculated with rhizobia prior to planting.


This new microorganism was extensively reviewed by EPA pursuant to its authority under the Toxic Substances Control Act (TSCA). Section 5 of TSCA requires that information about the health and environmental effects of new chemical substances (including new microorganisms) be reviewed by EPA before the substances may be used commercially in the United States. This review is conducted by EPA's Office of Pollution Prevention and Toxics. Information on new chemical substances or new microorganisms is submitted in the form of a premanufacture notice, or PMN. Each PMN for a new chemical substance or new microorganism receives a separate numerical designation; in the case of strain RMBPC-2, the PMN received the designation P92-403. Under TSCA, new microorganisms are those formed by combining genetic material from organisms in different genera (intergeneric). A genus (pl. genera) is a level in the taxonomic classification system used to group organisms based upon their similarity to other organisms.

EPA began evaluating various intergeneric strains of Sinorhizobium (Rhizobium) meliloti beginning in 1987. Research Seeds became involved in this research beginning in 1992, and submitted several PMNs for approval to conduct several small and large scale research field trials with various strains of these microorganisms, including strain RMBPC-2. These field trials included some strains developed by another company and previously evaluated by EPA. These field trials are subject to a Consent Order issued by EPA under section 5(e) of TSCA. The Consent Order, as amended, limits the use of the intergeneric strains of Rhizobium meliloti, including strain RMBPC-2, to specific sites only for research and development (R&D) purposes. The Consent Order went into effect on April 28, 1992, (the Order) and was subsequently modified in 1993 and 1994 to permit additional field trials at different sites.

On May 26, 1994, Research Seeds submitted a request to commercialize Rhizobium meliloti strain RMBPC-2. On January 4, 1995, a subcommittee of the Biotechnology Science Advisory Committee (BSAC) met to review the Agency's draft risk assessment. The BSAC is a panel of scientists from academia and other government agencies which functions as a peer review group for risk assessments of certain biotechnology products reviewed by EPA under TSCA. The BSAC submitted its report on March 6, 1995.

In September, 1997, EPA further amended the Consent Order to allow limited commercial use of S. meliloti strain RMBPC-2. This represents the first commercial use of an intergeneric microorganism in the environment under TSCA. The basis for the Agency's decision to allow the limited commercial use of this microorganismis summarized below.


The host microorganism used to produce RMBPC-2 was S. meliloti strain PC. Genes to enhance nitrogen fixation and nutrient utilization were added to the host strain. In addition, antibiotic resistance marker genes, which are used to isolate strain RMBPC-2 from other bacteria in the laboratory and in the environment, were also added to the host strain to create strain RMBPC-2. Based on evaluation of detailed information on the genetic modifications made to strain RMBPC-2, as summarized more fully below, EPA believes that these genetic changes are not expected to affect the microorganism's behavior in the environment.



Based on its assessment of available information, EPA believes that the initial commercialization of strain RMBPC-2 presents a low level of risk to health and the environment. In addition, strain RMBPC-2 has demonstrated a significant advantage over other commercial alfalfa seed inoculants in improving alfalfa yields under certain soil conditions. EPA acknowledges, however, that there are some uncertainties associated with the behavior of this microorganism in the environment, as noted above. Based on its intended use as a seed inoculant, the microorganism is expected to be produced insubstantial quantities and to be used in the environment in substantial quantities. EPA therefore believes that it is prudent at this time to limit commercial production of strain RMBPC-2, and to establish a subsequent opportunity for EPA to reexamine the product at a future date and to consider, in light of the information and understanding available at that time, whether additional action is needed to address questions about the behavior of strain RMBPC-2 in the environment.

For more information on this case, please contact the TSCA hotline at (202) 554-1404, TDD at (202) 554-0551. For more information on the TSCA Biotechnology Program, please visit the Program's homepage.

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