.. Table 4 Number of protein coding genes of Rhizobium leguminosarum bv. trifolii TA1 associated with the general COG functional categories. Acknowledgements This work was performed under the auspices of the US Department of Energy��s Office of Science, Biological and Environmental Research Program, and by the University of California, selleck chemical 17-AAG Lawrence Berkeley National Laboratory under contract No. DE-AC02-05CH11231, Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344, and Los Alamos National Laboratory under contract No. DE-AC02-06NA25396. We gratefully acknowledge the funding received from the Murdoch University Strategic Research Fund through the Crop and Plant Research Institute (CaPRI) and the Centre for Rhizobium Studies (CRS) at Murdoch University.

The authors would like to thank the Australia-China Joint Research Centre for Wheat Improvement (ACCWI) and SuperSeed Technologies (SST) for financially supporting Mohamed Ninawi��s PhD project.
An available source of nitrogen (N) is essential to life on Earth. Although the atmosphere consists of approximately 80% N, the overwhelming proportion of this is present in the form of dinitrogen (N2) which is biologically inaccessible to the vast majority of higher organisms. Only a subset of microbes has the necessary molecular machinery to make atmospheric N2 bioavailable by enzymatically reducing N2 to NH3. The fact that plant growth is most commonly limited by the availability of N may have provided the selective pressure for a wide range of plant genera, most of which are legumes, to evolve a symbiotic relationship with these N2-fixing microbes.

These microsymbionts, collectively termed root nodule bacteria, receive a carbon source from the plant and in return supply the host with biologically fixed N. When these symbiotic interactions are optimally harnessed in agriculture, all the N-requirements of the host can be met, without the need to apply industrially synthesized N-based fertilizers, thereby increasing both the economic and environmental sustainability of the farming system [1]. Forage and fodder legumes play an integral role in sustainable farming practice, providing feed for stock while also enriching soil with bioavailable N. Worldwide, there are approximately 110 million ha of forage and fodder legumes under production [2], of which members of the Medicago genus comprise a considerable component.

Two bacterial species, Ensifer meliloti and E. medicae are known to nodulate and fix N2 with Medicago spp. [3], although they differ in their symbiotic properties on some Medicago hosts. Specifically, while E. medicae can nodulate and fix N2 with M. murex, M. arabica and M. polymorpha, E. meliloti does not nodulate M. murex, does not fix with M. polymorpha and fixes N2 very poorly with Brefeldin_A M. arabica [4-6]. E.